Genetic Diversity Flashcards
Genetic diversity
Total number of alleles in a population
Caused by gene mutation, chromosome mutation, random factors with meiosis, fertilisation
Why is genetic diversity important
Disease, environmental factors will affect more people
Wider range of characteristics, more likely 1 will be advantageous to change
Gene mutation definition
Change in DNA base sequence of gene
Mutagenic agents
Environmental factors, increase rate of mutation above normal low rate
Mechanisms in cell identify, repair damaged DNA
Eg, toxic chemicals, ionising and high energy radiation in somatic cells
Chromosome mutations
Polyploidy in plants, while set of chromosomes changes
Non disjunction in meiosis, fail to separate, trisomy, Down’s syndrome
Substitution
1 nucleotide in DNA molecule replaced by another with diff base
Codon changed, forms diff amino acid, small change to protein formed
Silent mutation, degenerate codons
Deletion
Section of DNA lost, shift whole codon sequence by 1 base
Frameshift
Duplication
1 or more bases repeated
From shift
Inversion
Group of bases become separated from DNA sequence, rejoin at the same position but in reverse order
Changes amino acid formed
Addition
Extra base inserted into sequence
Frame shift
Translocation
Nucleotide groups separated from DNA sequence from DNA sequence on 1 chromosome, inserted into DNA sequence on different chromosome
Cancer, reduced fertility
Neutral mutation
Results in alleles that code for different sequence of amino acid in protein, do not affect function
Harmful mutation
Changes amino acid sequence, damages protein function
Beneficial mutation
Advantageous allele, survive, pass on allele, frequency of the allele will increase
Basis of evolution by natural selection
Antibiotic resistance
Bacteria have variation in gene pool, some more resistant
Exposed to antibiotic, kills majority
Resistant not killed, no competition for resources
Survive, reproduce, pass on allele/plasmid for antibiotic resistant to next gen
Frequency of antibiotic resistant allele/plasmid increases
Peppered moth
Peppered moths, silver allele
Live on silver birch, IR, sooty trees
Some had dark allele, advantage, camouflage
Dark moths, less likely to be eaten, survive, reproduce successfully, pass on dark winged allele
Population mostly dark
IR ends, silver trees, dark disadvantage
Silver less likely to be eaten, survive, successfully reproduce, pass on silver allele
Cystic fibrosis
Mucus too thick, can block lungs, other organs
Deletion mutation, faulty protein affects movement of chloride ions in water in and out of cells
No cure, can thin mucus with meds
Sickle cell anaemia
Affects people who live in areas with malaria
Cannot carry as much oxygen as normal erythrocytes leading to anaemia
Gene substitution, makes haemoglobin less soluble
Haemoglobin stick together, distort RBC
Block blood vessels, risk of heart failure
Natural selection
Representative of standard distribution of trait in organism
Directional selection pressure
Extra of trait experience selection against in it
Results in population trait distribution shifts towards other extremes
Stabilising selection pressure
Non extreme trait favoured instead of 2 extreme traits
Mean not shifted
