Genetic information, variation and relationships between organisms

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  • Created by: JosephPHS
  • Created on: 03-02-23 12:44
Eukaryotic Cells
Animal and Plant Cells
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Prokaryotic Cells
Bacteria
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Nuclear DNA in Eukaryotes
Linear DNA that exists as chromosomes found in the nucleus
Coiled around and associated with histones
Coiled tightly for compact storage

Mitochondria and chloroplasts have their own DNA similar to prokaryotic DNA
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Nuclear DNA in Prokaryotes
Circular and much shorter than Eukaryotic
Not associated with histones so supercoiled to fit into cell
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Mitochondrial/Chloroplast DNA
Similar to prokaryotic DNA
Circular
Short
Absence of protein
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Gene
Sequence of DNA that codes for a polypeptide or functional RNA
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Triplet Codon
A sequence of 3 bases that codes for an amino acid
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Start Codon
Triplet at the start of a gene that initiates translation
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Stop Codon
Triplet that causes ribosomes to detach, ceasing translation
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Degenerate Code
Different triplet codons can code for the same amino acid
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Universal Code
Triplet codons code for the same respective amino acid in every organism
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Non-Overlapping
Each base only belongs to one triplet codon and base sequence is read accordingly
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mRNA
Short single stranded RNA molecules found in the cytoplasm and nucleus

Formed during transcription giving a complementary sequence to parent DNA
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Functional RNA
Any RNA molecules other than mRNA that perform specific tasks in protein synthesis (tRNA and ribosomal RNA)
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tRNA
Type of functional RNA that allows amino acids to attach at the amino acid attachment site

Also contains an anticodon which is a complimentary codon the that of the RNA molecule

tRNA carries amino acids to ribosomes to make proteins
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Features of tRNA
Clover Shape
H bonds between base pairs hold shape together
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Introns
Sections of DNA that do not code for polypeptides and are removed via splicing

Only found in eukaryotes
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Exons
Sections of DNA that do code for polypeptides
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Genome
Collection of all genes within a cell
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Proteome
Full range of proteins a cell can produce
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Stage of Protein synthesis
Transcription
Translation
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Transcription
DNA helix unzipped to act as template
DNA helicase breaks H bonds between bases causing it to uncoil
Free mRNA nucleotides align to complimentary bases (T --> U)
RNA polymerase joins RNA nucleotides to create RNA chain
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Translation
mRNA is modified and leas the nucleus to attach to ribosomes
Ribosome attaches at the start codon
tRNA complementary to start codon aligns opposite mRNA (held in place by the ribosome)
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Translation (2)
Ribosome moves along one codon allowing complimentary tRNA to that codon to attach
The amino acids on the tRNA molecules are joined by a peptide bond catalysed by an enzyme requiring ATP
This repeats until the stop codon where the ribosome detaches
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Pre-mRNA
mRNA that contains introns which have not yet been spliced out

Only found in eukaryotes - Prokaryotes transcribe directly to produce mRNA
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Types of gene mutation
Insertion
Deletion
Substitution
Inversion
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Insertion
Extra nucleotide is inserted into base sequence causing frame shift
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Deletion
Nucleotide removed from base sequence causing frame shift
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Substitution
Nucleotide is replace by one with a different base
Does not lead to frame shift
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Inversion
Section of a chromosome detaches and reattaches in reverse order
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Non-disjunction mutation
Chromosomes/chromatids do not equally split when pulled to the poles in anaphase during meiosis
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Polyploidy
Change in the number of sets of an organism as a result of non-disjunction
All chromosomes in a set fail to separate equally
Can lead to production of diploid gametes (2 sets of chromosomes) and gametes with 0 sets of chromosomes following meiosis 2
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Aneuploidy
Change in the number of chromosomes within a set where homologous pairs within sets fail to separate results in gametes having one more or one less chromosome
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Meiosis
Cell replication that produces 4 daughter cells (gametes) each with half the number of chromosomes than the parent cell - 4 haploid cells
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Ways to introduce variation in meiosis
Crossing over
Independent segregation
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Independent segregation
When homologous chromosomes line up on the centre it is random which side the paternal and maternal chromosomes from each pair will lie
Pairs are then separated so each daughter cell contains a mixture of paternal and maternal chromosomes
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Crossing over
When homologous chromosomes line up chromatids can twist around each other with tension causing sections to break off
Broken sections of chromatids then recombine with another chromatid resulting in new combinations of alleles
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Genetic Diversity
The number of different alleles present in a population allowing natural selection
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Natural Selection
Alleles that provide a better chance of survival allow more organisms with that to reproduce whilst those without it are more likely to die out
This leads to an increase in the gene frequency of the advantageous allele
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Types of selection
Directional
Stabilising
Disruptive
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Directional selection
One extreme has selective advantage where selection pressure causes an increase in the frequency of the favoured extreme and modal trait (trait around midpoint) decreases
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Stabilising selection
Neither extreme is advantageous so modal trait increases with frequency of extremes decreasing
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Disruptive selection
Both extremes can be advantageous so modal trait decreases while both extremes increase
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Courtship behaviour
Sequence of actions (generally performed by males) unique to a species allowing animals to identify members of the same species to reproduce
Allows those of the opposite sex (generally females) to observe and decide whether they wish to mate
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Importance of Courtship
Successful mating
Species recognition
Synchronises mating behaviour
Indicates sexual maturity

Ensures survival of offspring by forming a pair bond and choosing a strong healthy mate
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Classification
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
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Hierarchy
Smaller groups arranged within larger groups
No overlap between group
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Types of Diversity
Species Diversity
Genetic Diversity
Ecosystem Diversity
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Species Diversity
The number of species (species richness) and individuals within each species in a community
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Species Richness
The number of different species within a community
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Genetic Diversity
Variety of genes amongst all the individuals in a population of one species
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Ecosystem diversity
The range of different habitats
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Farming techniques that reduce diversity
Destruction of hedgerows (habitat)
Selective breeding (reduces gene pool)
Monocultures (Soil erosion and pesticides)
Overgrazing (Damages ecosystems)
Filling in ponds and draining wetlands (habitat)
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Index of diversity
N(N-1)
D = -----------
Σ n(n-1)
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Other cards in this set

Card 2

Front

Bacteria

Back

Prokaryotic Cells

Card 3

Front

Linear DNA that exists as chromosomes found in the nucleus
Coiled around and associated with histones
Coiled tightly for compact storage

Mitochondria and chloroplasts have their own DNA similar to prokaryotic DNA

Back

Preview of the back of card 3

Card 4

Front

Circular and much shorter than Eukaryotic
Not associated with histones so supercoiled to fit into cell

Back

Preview of the back of card 4

Card 5

Front

Similar to prokaryotic DNA
Circular
Short
Absence of protein

Back

Preview of the back of card 5
View more cards

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