Genes and Inheritance

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  • Created by: JAlderman
  • Created on: 30-11-19 16:57
Define the word 'Genome'
All the hereditary material (coding and non-coding) of a particular organism.
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Lower eukaryotes have ? coding regions.
?= more
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Higher eukaryotes have more ? regions
?= Non-coding
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Coding regions are called?
Exons
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Non-coding regions are called?
Introns
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Prokaryotes have little or no ?
Introns
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Define the word 'gene'
Unit of hereditary information
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Genes are located at the ? of a chromosome.
?= locus
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How many genes in the human genome?
21,000
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Define and explain alleles.
Alternative form of genes. For Example: The gene may be eye colour; the alleles could be blue and brown.
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Repetitive DNA- Mini satellites= ?
VNTRs (Variable Number Tandem repeats).
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How many base pairs?
Can be 15 to 100 bp long.
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VNTRs varies from individual to individual and so can be used for ?
?= DNA fingerprinting
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Repetitive DNA- Micro satellites= ?
STRs (Short Tandem Repeats)
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How many base pairs?
2-6 bp in length
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STRs can be used for ?
?= DNA profiling
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Excessive nucleotide repeats causes disease; Name 2 diseases.
Fragile X Syndrome and Huntinton's disease.
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Define 'Dark DNA'
DNA which may appear to be missing but may be present.
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Describe genome evolution.
Mutation->Gene duplication-> Divergence->Phylogenetic Trees
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Mitochondrial DNA has ? genetic variance.
?= little
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mtDNA is inherited from the ?
?= mother
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mtDNA is used in ?
Forensic Science- Identifying unknown, badly decomposed or skeletal bodies.
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Annotation of a genome means
That we only describe coding regions within a genome.
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Prokaryotes have a ? but no nucleus.
?= nucleoid
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DNA is bigger than the cell and so has to be packaged. What are 2 other functions of packaging DNA?
1. To protect the DNA. 2. To regulate the DNA.
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What are the 2 parts of packaging DNA?
1. Looping 2. Supercoiling
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Loops condense DNA by ? fold
10
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Supercoiling is helped by ?
Type 2 Topoisomerases
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Supercoiling condenses by ? fold
100
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What removes supercoiling and induces relaxation of DNA?
Type 1 topoisomerases
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Removing supercoiling must be ?
local
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Therefore, topoisomerase 1 enzymes ? the backbone on a single strand.
?= nick (cut)
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What drugs target these enzymes to treat bacterial infections by preventing gne expression?
Fluroquinolones
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In prokaryotes, DNA replication travels ? until it reaches a specific site of ?
?= Bidirectional ?= Termination
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Name 6 differences between prokaryotic and eukaryotic DNA.
Prokaryotic DNA is: 1. Circular 2. Smaller 3. Not enclosed in nucleus 4. Supercoiled into nucleoid 5. No telomeres 6. Replication is efficient
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Define Plasmids.
Small, circular dsDNA found in the cytoplasm of the bacteria.
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Plasmid can be shared by 2 ways. What are these 2 ways?
1. Vertical inheritance 2. Horizontal Gene Transfer (HGT)
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Define operons
Co-regulated genes which do similar processes are grouped together and will be transcribed and translated together.
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What 4 parts make up the basic structure of operons?
Promoter, Operator, Structural genes and Polycistronic mRNA.
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Name 3 examples of operons.
1. Lac operon- is for the metabolism of lactose. 2. Trp operon- codes enzymes which synthesis tryptophan 3. ara operon- required to breakdown arabinose (5-carbon sugar)
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Give 4 reasons to why we look at prokaryotic genomics?
1. Understand evolution 2. Understand disease caused by bacteria and viruses and develop treatments 3. Genetic engineering 4. Synthetic biology
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Define gene expression.
Conversion of information encoded by a gene into a protein via an RNA intermediary
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Where does transcription take place?
Nucleus
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Where does translation take place?
Cytoplasm
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Define genotype.
Collection of genes in genome
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Define phenotype.
Collection of proteins in a cell
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All cells have the same genotype but have different phenotypes. Why?
Cells have different structures and functions.
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Define differentiation.
When a simple cell becomes a more specialised cell type.
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Monozygotic twins have identical genomes but have different phenotypes and look different as they get older. Why?
Due to changing conditions of the environment.
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Define epigenetics.
Heritable changes in gene expression that are due to environmental factors and random change.
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Why does DNA need to be packaged?
For protection and to fit into the nucleus.
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Define chromatin.
DNA with proteins that wrap and condense structure
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Primary protein component= ?
Histones
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How are nucleosomes formed?
Formed from DNA and histone proteins
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What is a chromatosome?
2 nulceosomes linked by H1 histone
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Define heterochromatin.
Condensed chromatin; usually contains repetitive DNA and not transcribed
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Define Euchromatin
Less condensed; contain unique sequences and involved in transcription
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Why can't transcription occur on heterochromatin?
RNA polymerase cannot access genes in heterochromatin and so can't be transcribed.
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What are the 2 main ways that the change between euchromatin and heterochromatin are regulated?
1. Histone modification 2. DNA methylation
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Define histone modification.
Modification to the N-terminus (tail) of histone influences DNA-histone binding relationship.
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How is the binding relationship between DNA and histones affected by modification.
The electrostatic interaction is changed.
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What charge does DNA have?
Negative charge
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What charge does histones have?
Positive charge
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What are the 4 types of modification in histone modification.
1. Acetylation 2. Methylation 3. Phosphorylation 4. Ubiquitination
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Define acetylation.
Addition of acetyl to lysine and reduces positive charge of histone
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What enzyme is used?
HAT (Histone Acetyl Transferase).
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True of false; Acetylation causes transcriptional activation (euchromatin).
True
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Define methylation.
Addition of methyl to lysine or arganine.
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What enzyme is used?
HMT (Histone methyl transferases)
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Define phosphorylation.
Addition of phosphate groups at serine and theonine.
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Define Ubiquitination
Small protein added at lysine
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Define DNA methylation
Addition of methyl group to DNA at Cytosine of CpG islands.
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What enzyme is used?
DNMT (DNA Methyl Transferase)
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True or False; DNA Methylation causes transcriptional activation while DNA Demethylation causes transcriptional silencing.
False- Its the other way round.
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What 8 factors affect epigenetic code?
1. Stress 2. Exercise 3. Smoking 4. Alcohol 5. Drugs 6. Pathogens 7. Weather 8. Diet
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True or False: Type 1 Promoters have a TATA box
False
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What region do they have instead of a TATA box?
DPE (Downstream Promoter Element)
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Both Type 1 and 2 Promoters have an ?
?= Initiator Region (InR)
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What is the first step of forming the pre-initiation complex on a Type 2 Promoter?
TBP (TATA box binding protein) binds to TATA
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What is the second step of forming the pre-initiation complex on a Type 2 Promoter?
TAFs (TBP Associated Factors) bind to TBP
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What is the final step of forming the pre-initiation complex on a Type 2 Promoter?
TFIID recruits TFIIA-H and RNA polymerase II to form pre-initation complex.
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In the pre-initiation complex, TFIIA binds to ?
?= TFIID
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In the pre-initiation complex, TFIIB binds and forms ?
?= DAB complex
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RNA polymerase II is bound by ? which binds to DAB complex.
?= TFIIF
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? and TFIIH bind and form TS pre-initiation complex.
?= TFIIE
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? phosphorylates amino acids of RNA polymerase II
?= TFIIH
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TFIIB e.c.t are known as ?
General Transcription Factors or Basal Transcriptional factors
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What are the 4 Cis regulatory elements?
1. Promoters 2. Enhancers 3. Silencers 4. Insulators
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What are the 2 Trans regulatory elements?
1. Activators 2. Repressors
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True or False: Trans regulatory elements bind to Cis regulatory elements.
True
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Define Activators.
Regulatory proteins which bind to site on DNA called enhancers. They increase transcription.
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Define Repressors.
Regulatory proteins which bind to silencer sites on DNA. They decrease transcription.
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It is possible for regulatory proteins to serve as activator in one cell and a repressor in another. Give an example of a system which shows this.
Myc-Max-Mad system
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Max travels around in a ?
?= Homodimer
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True or False: Max can bind to the DNA.
True
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When Myc binds with Max or Mad binds with Max a ? is formed.
?= Heterodimer
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When Myc is expressed=
Myc-Max heterodimer formed and transcription is activated.
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When Mad is expressed=
Mad-Max heterodimer formed and transcription is repressed.
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Name 4 Post transcriptional modifications.
1. 5' Capping 2. 3' polyadenylation 3. Splicing 4. RNA Editing
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Explain the process of 5' Capping.
1. 5' end is a triphosphate 2. One of the phosphate groups is removed= bisphopsphate 3. GTP is added by mRNA gunylyltransferase 4. 7-nitrogen of guanine is methylated by mRNA (guanine-N7)-methyltransferase
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Give 4 reasons why 5' capping is important.
1. Protects mRNA from degradation 2.Important for removal of first intron 3. Allows efficient export from nucleus 4. Provides a ribosome binding site for initiation of translation
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Explain the process of 3' polyadenylation.
1. 3’ ends a poly tail of up to 250 A’s 2. Mammals: pre-mRNA is cleaved 15-30 nucleotides after the 5’AAUAAA3’
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Give 2 reasons why 3' polyadenylation is important.
1. Tail required for final intron removal 2. Enhances stability and translation
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Define splicing.
Splicing- Removal of introns from mRNA
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Group 1 introns are 1. and require the formation of 2. structures.
1.= Self-splicing 2.= Stem-loop
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What are the 3 sequences of Eukaryotic Protein-Mediated Splicing?
1. Splice Donor 2. Splice Acceptor 3. Lariat Branch Point
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Splicing in higher eukaryotes is protein-mediated. These proteins together with some RNA form the ?
Spliceosome
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The U6-U2 complex do what?
Catalyse reaction that generates lariat formation
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True or False; U3 binds to U2.
False- There is no U3; U4, U5, and U6 form a single particle and bind to U2.
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Define alternative splicing.
Regulated process during gene expression that results in a single gene coding for multiple proteins.
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The different products arising from alternative splicing known as ?
?= Splice variants
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Name a type of alternative splicing.
Exon skipping
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Define trans splicing.
When 2 exons from 2 different mRNA are joined end to end and ligated.
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Ribosomes bind to the ? sequence in prokaryotic mRNA.
?= Shine Dalgarno
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True or False: protein structure is not fixed.
True
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One way protein structure is dictated is ?
PTMs (Post Translational Modifications)
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Define Post Translational Modifications (PTM).
Chemical modifications which occur after protein translation.
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True or False: There are >300 types of modification.
True
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Name the 5 main types of PTM.
1. Addition of small chemical groups 2. Addition of complex molecules 3. Addition of small proteins 4. Modification of amino acids 5. Cleavage
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Which of these 5 modifications are reversible?
Addition of chemical groups, Addition of complex molecules, Addition of polypeptides.
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Which are irreversible?
Amino Acid Modification and Cleavage
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Name 3 examples of modification which add chemical groups.
1. Phosphorylation 2. Acetylation 3. Methylation
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Name 1 example of modification which adds a complex molecule.
Glycosylation
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Name 1 example of modification which adds a polypeptide.
Ubiquitination
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Explain proteolysis- cleavage.
The cleavage of peptide bonds within the primary amino acid sequence.
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What enzyme is used to do this?
Peptidases
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Give an example of cleavage.
Cleavage of proinsulin to form mature insulin
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Disulphide linkages are ?
?= reversible
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How do disulphide bonds form?
Form between thiol (SH) groups of neighbouring cysteine residues
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True or False: SH groups are highly reactive and easily oxidised.
True
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True or False: Disulphide groups are not dynamic and cannot respond to the cell's environment.
False
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PTM occurs at specific residues: What are the residues for phosphorylation?
Ser,Thr, Tyr
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PTM occurs at specific residues: What are the residues for Acetylation?
Lys
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PTM occurs at specific residues: What are the residues for Methylation?
Arg and Lys
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PTM occurs at specific residues: What are the residues for Oxidation/nitrosylation?
Cys
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PTM occurs at specific residues: What are the residues for lipidation?
Cys
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PTM occurs at specific residues: What are the residues for Ubiquitnation?
Lys
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PTM occurs at specific residues: What are the residues for Glycosylation?
Asn, Ser, Thr
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How are PTMs attached to the protein.
Enzymes
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Phosphorylation uses the enzyme ? to add phosphates.
?= Protein Kinase
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Not every residue is modified; PTM residues are found in a ?
?= Consensus site/sequences
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Define consensus sequence.
The specific sequence of amino acids surrounding a site of a post translational modification
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True or False: enzymes act at their own particular consensus site.
True
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What 4 things does PTM regulate?
1. Function 2. Confirmation 3. Folding 4. Localisation
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Give 5 reasons why the cell uses PTM to modify protein function.
1. PTM enables cells to rapidly respond to their environment 2. PTM alters chromatin structure 3. PTM alters gene expression 4. PTM convey information about cell stress and metabolic state 5. PTM regulate Protein stability and turnover
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How does PTM enable cells to rapidly respond to the environment?
Phosphorylation is essential for signal transduction; Addition/removal of phosphates=Activation/inactivation of proteins within signalling cascade.
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How does PTM alter chromatin structure?
Histones are subject to many PTMs; acetylated, methylated and phosphorylated.
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How does PTM alter gene expression?
PTM alters packaging of hisotnes and so presence of gene promoters of chromatin: Euchromatin= open, Heterchromatin= closed
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How does PTM convey information about cell stress and metabolic state?
Cysteine residues are sensitive to ROS; can trigger non-native disulphide formation and so alter protein conformation. Also PTM uses many metabolites as substrates and so metabolic state can influence.
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Define ROS.
Reactive Oxygen Species- Chemically reactive species containing oxygen; For Example- Peroxides
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How does PTM regulate protein stability and turnover?
Ubiquitination is important modification that can target proteins for degradation.
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How? (further explain)
Multiple ubiquitin molecules= Polyubiquitin chains Polyubiquitinated proteins are targeted to the proteasome for destruction.
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Define SUMO.
SUMO- A ubiquitin-like molecule which acts like ubiquitin
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What enzymes does ubiquitin require?
E1, E2 and E3
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What enzyme can be used to remove ubiquitin?
DUB (Deubiquination enzymes)
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True or False: PTMs will compete for a common residue.
True
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Give an example of reciprocal modification.
Acetylation or Methylation
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Give an example of sequential modification.
Ubiquitination occurs after phosphorylation/oxidation/acetylation of neighbouring residues
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Define DNA damage.
Alteration in the chemical structure of DNA molecule (abnormal structure)
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Give 3 examples of DNA damage.
1. A break in a strand of DNA 2. A base missing from the backbone of DNA 3. A chemically modified base
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Define mutation.
A change in the sequence of standard base pairs/ Changes in nucleotide sequence of DNA
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DNA damage leads to premature ?
?= Cellular senescence/Cellular ageing
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Define Cellular senescence
Irreversible growth arrest
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Cellular senescence means ?
?= The cell can no longer divide and so apoptosis occurs.
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Define Apoptosis.
Programmed cell death
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True or False: Usually apoptosis is highly regulated and controlled.
True
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Cell debris is engulfed by ?
?= phagocytes
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Define Necrosis.
Form of traumatic cell death that results from acute cellular injury: For Example- Extreme heat or decrease in O2.
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Define Hayflick limit.
A normal cell will divide 75-100 times before entering senescence
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The Hayflick limit is dictated by ?
?= Telomere length
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Define Telomeres
Repetitive DNA at each end of chromosomes
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True or False: Telomeres shorten by each cell division and so the length of telomeres determines number of times DNA can be replicated.
True
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Telomeres are protected by ?
?= Shelterin (protein complexes)
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True or False: Shelterin allows access of DNA repair proteins.
False- Shelterin prevents access
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Name the enzyme which increases the length of telomeres.
Telomerase
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This enzyme counteracts ?
?= Cellular ageing
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What animal is reported to be immortal as it is not subject to the Hayflick limit.
Lobsters
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What are the two types of sources that causes DNA damage?
Endogenous and Exogenous sources
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What are the 4 endogenous sources?
ROS, DNA Replication, Hydrolysis reactions and Deamination
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How do ROS cause DNA damage?
ROS normal by-product of metabolism of oxygen but if ROS level is too high causes damage as ROS chemically modify a nucleotide and can interfere with the hydrogen bonding in DNA.
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How does DNA replication cause DNA damage?
When cells divide they make a copy of DNA but this may have mistakes (usually incorrect base pairing). However these errors are low due to exonuclease domain in polymerase complex
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How does hydrolysis reactions cause DNA damage?
Depurination- The base (purine) is cleaved from the nucleotide; this means cannot be read.
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How does deamination cause DNA damage?
Amine group is cleaved from nitrogenous base which means that cytosine bases are turned into uracil; this means that it is read as thymine in DNA.
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What are 2 endogenous sources?
1. UV 2. Intercalating DNA agents
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How does UV cause DNA damage?
Above 260nm= distort bonds and DNA
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How does intercalating DNA agents cause DNA damage?
Structural modifications lead to functional changes and so DNA cannot be replicated or transcribed; For example Ethidium Bromide.
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True or False: Repair mechanisms are specific to the type of DNA damage.
True
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Give a condition which can be gained if DNA repair mechanisms fail
Xeroderma Pigmentosum
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True or False: Mutation can occur both in somatic (not passed to offspring) and gamete (passed to offspring) cells.
True
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Mutation occurs daily but does not always affect us because (3 reasons):
1. Depends on location of mutation 2. May occur in gene realted region but have no effect (neutral mutation) 3. May be beneficial (advantageous mutation)
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Mutations can be 1. or 2.
1. small 2. large
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What are the different types of small scale mutations (nucleotides)?
1. Insertions 2. Deletions 3. Substitutions- point mutations
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Fragile X syndrome is an insertion mutation of ?
CGG repeat
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In terms of substitutions; a purine swapped to a purine or a pyrimidine swapped to pyrimidine is known as ?
?= Transitions
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In terms of substitutions; a purine swapped to a pyrimidine or vice versa is known as ?
?= Transversions
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Name and define the 3 types of point mutations.
1. silent= code for same amino acid 2. Missense= Code for different amino acid 3. Nonsense= Code for a stop codon
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What are the different types of large scale mutations (regions)?
1. Deletion 2. Duplication 3. Inversions
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Define advantageous mutation.
A mutation which is beneficial; increases fitness of organism.
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Define neutral mutation.
A mutation that does not affect fitness of an organism
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Give an example of a neutral mutation.
Mutation of MC1R gene causes red hair
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Define deleterious mutation
A mutation which reduces fitness of an organism.
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Example?
Hutchinson-Gilford Progeria- mutation in LMNA gene.
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True or False: Detrimental mutation not always fatal but disadvantageous to the organism.
True
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Define Autosomal Dominant.
Mutated allele of gene is dominant; always expressed over recessive- carriers will always have disease.
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Example?
Huntington disease
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Define Autosomal Recessive
Mutated allele is recessive, not expressed over dominant (unmutated)- Carriers will not have disease but will have a single recessive allele
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Example?
Cystic fibrosis and sickle cell disease
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What is Preimplantation Genetic Diagnosis better known as?
Embryo screening
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Define haemoglobin disorder.
Inherited blood diseases that affect how oxygen is carried in the body.
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Give example.
Sickle cell disease and thalassaemias
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Define HOX genes.
Genes that control segment identitiy
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What are HOX genes called in humans?
Homeobox
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Mutations of HOX genes can ?
Transform one body part into another.
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Define Horizontal Gene Transfer.
The acquisition of exogenous DNA by prokaryotes (Bacteria better understood)
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Name the 3 different methods.
1. Transformation 2. Conjugation 3. Transduction
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True or False: Traits involved are not transferred by inheritance from one generation to the next but introduced from unrelated individuals or from a different species.
True
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DNA transfer is asymmetrical in 2 ways:
1. Transfer goes in one direction 2. Most recipients relieve 3% or less of a donor's DNA
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Give 2 reasons why prokaryotes transfer genes?
1. Enables rapid adaptation of prokaryotes to new environments 2. Contributes to the evolution of the prokaryotic genome
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Donor DNA can come from, what 3 bacterial sources?
1. Plasmids (most common) 2. Insertion sequences 3. Transpoons (an insertion sequence but larger)
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Donor DNA from a virus is in the format of ?
Transducing phages
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Transformation was discovered in ?
?= 1928
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Transformation was confirmed in ?
?= 1944
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Define Transformation.
DNA fragment/plasmid taken up from environment
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Similar process in eukaryotes= ?
?= Transfection
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Explain transformation.
1. DNA binds to cell surface receptors 2. Free donor processed by cell surface enzymes- nicked, digested by endonuclease 3. DNA taken up through protein/poly hydroxybutyrate- calcium polyphosphate translocation channel.
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Continued
4. DNA integrated by recombination in recipient; requires RecA
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Conjugation was discovered in ?
?= 1946
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Define conjugation.
Transfer of DNA from donor to recipient cell via direct contact through a conjugation/sex pilus.
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Recipients after conjugation are known as ?
?= trans-conjugants
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The F Plasmid=
Conjugative plasmid of E.coli
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The F plasmid encodes ?
?= Transfer genes (proteins are needed for pilus formation and nicking enzyme)
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Donor cells are ?
?= F+
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Recipient cells are ?
?= F-
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Plasmids encoding antimicrobial resistance=
R plasmid
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Transduction was discovered in ?
1952
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Define transduction
Bacterial DNA transferred between donor and recipient bacterium via a virus
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The virus is said to be a vector and is a ?
bacteriophage or phage
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True or False: Phages are very specific to cell surface receptors.
True
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Recipients are called?
?= transductants
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The fate of DNA in a recipient depends on ? (2 things)
1. Type of phage (lysogenic or Lytic cycle) 2. DNA transferred
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Define Lysogenic cycle.
Integrates into genome or replicates as plasmid.
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Define Lytic cycle
Replicates immediately, producing more phages.
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What are the 2 types of transduction?
1. Generalised 2. Specialised
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Explain Generalised transduction.
Phage infects donor, donor DNA broken down as well as phage DNA, one phage packages donor DNA and infests recipient and recombination occurs. Recipient cell has mixture of donor and its own DNA.
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True or False: any bacterial gene can be transferred in generalised transduction.
True
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True or False: Generalised transduction is common.
False- It is rare
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Example of generalised transduction.
E.coli P1 phage
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Explain Specialised transduction.
Prophage infects donor, prophage exchanges DNA with donor (donor has some of the phage DNA). Phage transfers DNA segment with host DNA and Phage DNA to recipient cell; recombination occurs. Recipient cell contains Donor, phage and its own DNA.
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True or False: Specialised transduction is rare.
True
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Example of Specialised transduction.
E.coli Phage Lambda
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Define Melanin
A pigment found in most organisms.
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How is melanin produced?
Oxidation of tyrosine in cells called melanocytes
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3 types of melanin are produced; What are they?
1. Eumelanin 2. Phaeomelanin 3. Neuromelanin (nerves)
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What colours does Eumelanin produce?
black/brown
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What colour does phaeomelanin produce?
red/yellow
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What is the main function of melanin?
Protect organisms from cell damaging agents: For Example UV
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melanocytes are stimulated to make melanin by ?
?= MSH (Melanin Stimulating Hormone)
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What controls the release of hormones ?
Hypothalamus gland
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MSH is 13 amino acids long and binds to ? found on the melanocyte cell surface which produces eumelanin.
?= Melanocortin 1 receptor (g-couple receptor)
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Define agouti gene.
A gene that controls melanin in mammals that dictates their coat colour and pattern.
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The product of the agouti gene is ?
?= ASIP (Agouti Signalling Protein)
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ASIP acts as inverse agonist causing melanocytes to produce ?
?= phaeomelanin
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When MSH binds to receptor, tyrosine is converted into ?
?= DOPA
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DOPA is then converted into ?
?= DOPA Quinone
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The end product is ?
?= DOPA chrome= Eummelanin
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This process is ? cAMP
?= High
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When ASIP binds to the receptor, tyrosine is converted into ?
?= DOPA
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DOPA is then converted into ?
?= DOPA Quinone
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Adding cysteine then produces the end products which is ?
?= Cysteinyl DOPA= Phaeomelanin
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Define Single Nucleotide Polymorphism (SNPs)
Substitution of a single nucleotide that occurs at a specific position in the genome.
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There are 1. common SNPs in the 2. gene which when present as homozygous alleles will give rise to red hair.
1. 4 2. MC1R
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In the example of the agouti mouse, what happens when the gene is methylated ?
mRNA made in development only and healthy brown mouse.
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In the example of the agouti mouse, what happens when the gene is non-methylated ?
mRNA is made throughout life and yellow and obese mouse which develops type 2 diabetes.
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In sheep there are 2 copies of the ?
?= agouti gene
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If both copies have tandem repeats ?
agouti expressed
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However...
A recessive black non-agouti allele of ASIP can be carried by white sheep.
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Both MSH and ASIP are regulated by what 3 things ?
1. Day length 2. Temperature 3. Other homones
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Define photoperiodism.
The response of an organism to seasonal changes in day length,
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Define Albinism
Congenital absence of any pigmentation in a person, animal or plant resulting in white hair and pink eyes.
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What is the affected gene that causes albinism ?
TYR gene- Can't make enzyme needed to make melanin
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Colouration in birds is created in 2 ways:
1. Light (reflection by feathers) 2. Pigments
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What colour is produced by light ?
Blue
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What are the 3 pigments in birds ?
1. Melanin 2. Porphyrins 3. carotenoids
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How are porphoryrins produced and what colour ?
Produced through amino acid metabolism; colours: red, pink and green.
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How are carotenoids produced and what colour ?
From plants and must be consumed; colours: reds, bright yellows and greens
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Panther chameleons have specialised cells called ? in their skin.
?= Iridophores
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Iridophores contain small close packed crystals of ? which change shape in reaction to nerve impulses.
?= guanine
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Define heterosis.
Improvement or increased function of any biological quality in a hybrid offspring.
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Give an example.
Labradoodle- those allergic to dogs are not allergic to labradoodles
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Define cloning.
To produce an organism that is genetically identical to its parent.
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Define epistasis
The effect of one gene is dependent on the presence of one or more 'modifier genes', i.e. the genetic background.
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Define codominance
A relationship between two versions of a gene (allele).
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Define incomplete dominance
One allele for a specific trait is not completely expressed over its paired allele.
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Other cards in this set

Card 2

Front

Lower eukaryotes have ? coding regions.

Back

?= more

Card 3

Front

Higher eukaryotes have more ? regions

Back

Preview of the front of card 3

Card 4

Front

Coding regions are called?

Back

Preview of the front of card 4

Card 5

Front

Non-coding regions are called?

Back

Preview of the front of card 5
View more cards

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