Genetics of living systems

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Define mutation
Changes in the arrangement or amount of bases in the sequence of DNA
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Define chromosome mutation
Changes to part of or whole of a chromosome
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Define DNA mutation
Changes to genes due to changes in nucleotide base sequence
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What are factors which cause mutation?
Tar, uv light, xrays, gamma rays, free radicals
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How do free radicals cause mutations?
By affecting the structure of the nucleotide which can disrupt base pairing in DNA replication
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What level of structure does a mutation in DNA bases affet?
Primary causing a domino effect for the rest of the protein
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What is frameshift mutation ?
When a mutation causes a shift in the triplets which follow the mutation changing the way the rest of the base is read
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What is the difference in effect between an early frameshift and later frameshift?
Earlier the greater effect as more codons are affected
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What is a substitution?
Swapping one or more of the bases for another one
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What is a nonsense mutation?
When the mutation stops the codon being coded for
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What is a missense mutation?
When a different amino acid is coded for
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What level of structure is effected due to a missense mutation?
Primary which has a knock on effect for the other structures
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What is a silent/ neutral mutation?
When the same amino acid is being coded for
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How can a mutation mean the same amino acid is coded for?
Because the genetic code is degenerate so the same three bases can code for the same amino acid
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What is another example of a silent/ neutral mutation?
When the amino acid changes but is chemically similar to the amino acid before so there is no physical change
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What are two other types of mutation?
Insertions and deletions
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How can a mutation benefit an organism?
It can produce an advantageous characteristic for the organism increasing their chance of survival
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How can a mutation be harmful?
It can produce a disadvantageous characteristic decreasing their chance of survival
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Define conservative mutation
When the amino acid being changed has similar properties so the effect is less servere
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Define non conservative mutation
When the amino acid is chemically different to the original one causing a more servere effect
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What are the 4 chromosome mutations?
Deletion, duplication, translocation, inversion
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What is a deletion chromosome mutation?
When a section of chromosome breaks off into the cell
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What is a duplication chromosome mutation?
When sections of the chromosome are duplicated
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What is a translocation chromosome mutation?
When a section of chromosome breaks off and joins another homologous chromosome
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What is an inversion chromosome mutation?
When a section of chromosome breaks off, is reversed, and then joins back onto the chromosome
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Define gene
Length of DNA which codes for polypeptides
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What are the three types of RNA?
MRNA, tRNA, rRNA
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What is the role of RNA polymerase?
To attach to the DNA and break the hydrogen bonds between the bases
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What is transcription?
When the unzipped strand of DNA is read by RNA polymerase and free nucleotides in the nucleus are lined up complementary
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What happens to the free nucleotides after they’ve been lined up and RNA polymerase has passed?
Hydrogen bonds bond them together
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What makes RNA polymerase stop?
When it reaches a stop codon
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How does mRNA leave the nucleus?
Through the nuclear pore
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Where does the mRNA go after they’ve left the nucleus ?
Attaches to the ribosome
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Where are two places ribosomes can be found inside the cell?
On the rough ER or free in the cytoplasm
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How are ribosomes made?
In the nucleus by rRNA and a protein
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What is tRNA?
Another form of RNA which carries amino acids to the mRNA on the ribosome
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What bonds form between the amino acids?
Peptide bonds
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How is gene expression controlled at transcriptional level?
Genes can be turned on and off
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How is gene expression controlled at post transcriptional level?
MRNA can be modified which regulates translation and the types of proteins produced
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How can gene expression be controlled by translation?
Translation can be stopped and started by stop and start codons
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How is gene expression controlled at post translational level?
Proteins can be modified after synthesis which changes their function
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How can increasing transcription lead to more proteins being made?
Means more strands of mRNA are made which is used to make more proteins
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What is the rate of transcription controlled by?
Transcription factors
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What are transcription factors?
Proteins which bind to DNA and switch genes on and off by increasing or decreasing the rate of transcription
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What are transcription factors which start transcription called?
Activators
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What are transcription factors called which stop transcription?
Repressors
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What does the lac operon gene do?
Produce proteins to break down lactose into galactose and glucose
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What does lactose bind to?
A repressor protein
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How does lactose effect the repressor protein?
It changes shape and leaves the gene
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What happens when the repressor protein leaves the gene?
The promoter is uncovered and RNA polymerase breaks the hydrogen bonds and mRNA is formed from free nucleotides
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What three proteins are made from the lac operon?
Beta galactosidase, lactose permease and transactylase
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What does beta galactosidase do?
Break down lactose into glucose and galactose
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What does lactose permease do?
Makes the cell wall more permeable to lactose
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What does transactylase do?
Moves an acetyl group to a co enzyme
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How is the lactose digestion stopped?
Lactose leaves the repressor protein and the repressor protein binds back to the gene so RNA polymerase cannot attach
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What is heterochromatin?
Tightly wound sections of DNA causing chromosomes to be visible during cell divison
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What is euchromatin?
Loosely wound DNA present during interphase
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Why is transcription not possible at heterochromatin?
Because the DNA is tightly bound so the RNA polymerase cannot attach to the gene
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How does histone modification increase or decrease transcription of genes?
Adding a acetyl group reduces charge on histones so DNA coils less meaning the genes can be transcribed easier
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What effect does adding methyl to a histone effect ?
Causes the dna to coil more decreasing transcription
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What is an intron?
Genes in eukaryotic DNA that don’t code for amino acids
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What is an exon?
Parts of DNA which code for amino acids
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What is the process called which removes introns?
Splicing
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What is mature mRNA?
mRNA which has undergone splicing and only contains Exons
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What end of the mRNA is a cap added to?
5’ end (a modified nucleotide)
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What end of mRNA is a tail added to?
3’ (long chain of adenine nucleotides)
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Why is a cap and tail added to a nucleotide?
Helps to stablise the mRNA and delay degradation, and the cap helps mRNA to bind to the ribosomes
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What are the three ways protein synthesis is regulated after translation?
mRNA degrades, inhibitory protein binds to mRNA to stop ribosomes binding, activation of initiation factors which aid mRNA binding to ribosomes
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What are the ways proteins are modified at post translational level?
Molecules activate the protein, addition of non protein groups, folding/ shortening of proteins, molecules bind to cell membrane and trigger cAMP to alter a proteins 3D structure
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Define morphogenesis
Regulation of the pattern of anatomical development
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Why do we use fruit flys to study body plans?
Small and easy to keep, reproduce quickly, cheap
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How do proteins influence body plans?
Some proteins activate or repress transcription of developmental genes
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What are homeobox genes?
A group of regulatory genes which contain a homeobox sequence
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What is the homeobox sequence?
Section of DNA 180 base pairs long which makes a protein which is 60 amino acids long
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What three organisms is the homeobox sequence similar in?
Plants, animals and fungi
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What is the homeodomains function?
Joins onto another protein to make a molecule which binds to a specific site on DNA to switch genes on and off
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What effect does proteins binding onto DNA at the start of developmental genes have?
They activate or repress transcription altering production of proteins involved int he development of body plans
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What are hox genes?
A group of homeobox genes found only in animals
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What are homeobox gens responsible for?
The correct positioning of body parts
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What are homeobox genes found in ?
Gene clusters
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How many hox genes are found in drosophila?
2 hox genes clusters so 8 in total on chromosome 3
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What do the two hox genes found in dropsophilia control?
1- development of head and anterior thorax, 2- prosterioir thorax and abdomen
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Define radical symmetry
Diploblastic animals- have no right or left side only top and bottom
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Define bilateral symmetry
Left and right symmetry with head and tail
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Define asymmetry
Seen in sponges- no lines of symmetry
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Define apoptosis
Programmed cell death
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How does apoptosis help in the developmental stage of life?
Removes unwanted cells and tissues to cause body parts to be shaped
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What is the significance of apoptosis releasing chemical signals?
To stimulate mitosis and cell proliferation causing the remodelling of tissue
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What genes regulate mitosis and apoptosis?
The hox genes
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What are examples of where apoptosis and mitosis are used?
Menstruation, tadpoles turning into frogs, broken bones, development of the nervous system
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What is syndactyly?
When fingers and toes are webbed so apoptosis hasn’t occurred in these cases
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What is the first stage of apoptosis?
Enzymes inside the cell break down cell components
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What is the second stage of apoptosis?
The cell shrinks and begins to fragment
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What is the third stage of apoptosis?
Phagocytes engulf and digest cell fragments
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Which environmental internal stimuli effect regulatory genes?
DNA damage, release of hormones; growth hormones or cytokines
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What are the external environmental stimuli that effect regulatory genes?
Stress by lack of nutrients, attacks by pathogens, temperature changes, light intensity
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What is an example drug which effects regulatory genes?
Thalidomide prevents the expression of hox genes
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What is thalidomide now used to treat ?
Some tumours (cancer medicine)
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Other cards in this set

Card 2

Front

Define chromosome mutation

Back

Changes to part of or whole of a chromosome

Card 3

Front

Define DNA mutation

Back

Preview of the front of card 3

Card 4

Front

What are factors which cause mutation?

Back

Preview of the front of card 4

Card 5

Front

How do free radicals cause mutations?

Back

Preview of the front of card 5
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