Genetic diversity Flashcards
Types of DNA mutation
Substitution of bases, deletion of bases, chromosome mutations
Substitution DNA mutation
When nucleotide in DNA is replaced by different nucleotide. DNA triplet produces different amino acid, different polypeptide chain, protein different shape, not functioning.
Degenerate coding means not always different amino acid.
Deletion of base DNA mutation
Single nucleotide lost from DNA sequence. Causes all triplets after it to be read incorrectly.
Chromosome mutation
Change to whole set of chromosomes: 3 or more sets instead of 2.
Changes in number of individual chromosomes: Homologous pairs fail to separate in meiosis. Results in offspring having more or fewer chromosomes.
Meiosis
Meoisis I: IPMATC, pairs of homologous chromosomes separated.
Meoisis I: PMATC, sister chromatids separated.
How does meiosis bring about genetic variation
The segregation of homologous chromosomes is independent.
Crossing over, causing new combinations of alleles.
Also random fertilisation
Independent segregation of chromosomes brings variation how
In meiosis I, homologous chromosomes line up randomly across the middle, meaning that combination of chromosomes in daughter cell is random.
Crossing over brings variation how
Chromatids become twisted around one another, causing portions of chromatids to break off and recombine during meiosis I.
Formula for number of possible chromosome combinations in a cell
2^n
where n = number of pairs of homologous chromosomes.
Formula for number of possible chromosome combinations in a cell (including random fertilisation)
(2^n)^2
where n = number of pairs of homologous chromosomes.
Genetic diversity def
Number of different alleles of genes in a population
What allows natural selection to occur
Genetic diversity increases number of alleles = more chance of characteristic that suits population = natural selection and evolution
Natural selection and evolution explanation
Gene pool may have a random mutation that results in new allele of gene that may give possessor advantage.
Better adapted to survive, more likely to survive compared to competition and reproduce.
Allele more likely to be passed on.
Advantageous allele becomes more prominent in population.
Directional selection
Individuals with phenotypes that vary in one direction of mean are favoured by selection. Their alleles are more likely to be passed on and the mean moves in that direction.
One extreme favoured and one extreme favoured against.
Stabilising selection
Individuals with phenotypes that remain closest to the mean are favoured and are more likely to pass on alleles. Eliminates phenotypes at the extremes.
