9: Genetic diversity and adaptation

change to the quantatity or base sequence of DNA in an organism

change in nucleotide bases or sequence of bases
results in formation of new allele

• a nucleotide is replaced by a nucleotide that has a different base

• new triplet may code for a different amino acid

• polypeptide produced will differ in a single amino acid

• if amino acid is involved in forming bonds to form the tertiary structure of the final protein, then the replacement amino acid may not from the same bonds

• different shape of protein which may mean that it doesn’t function properly

a nucleotide is lost from the DNA sequence
causes triplets to be read in a different order

occurs when organisms have three or more sets of chromosomes rather than two

individual homologous pairs of chromosomes fail to separate during meiosis (non-disjunction)
results in gamete having one more or one less chromosome

homologous chromosomes pair up and their chromatids wrap around each other
by the end of this division homologous pairs have separated with one chromosome of each pair going into one of the two daughter cells

chromatids move apart
at the end of meiosis 2 four cells have been formed

independant segragation
crossing over
different alleles for the same gene

arrangement of homologous pairs is random
combination of chromosomes from paternal and maternal origin that go into daughter cells at meiosis 1 is random

chromatids of each pair become twisted around eachother
tensions are created and portions of chromatids break off
equivalent portions of homologous chromosomes exchanged
new combinations of maternal and paternal alleles produced

2 to the power of n
n=number of homologous pairs

total number of different alleles in a population

the process that leads to evolution in populations

change in allele frequency over many generations in a population

1. new alleles for a gene are created by random mutation

2. if the new allele increases the chances of the individual to survive in that environment they are more likely to survive and reproduce

3. this reproduction passes on the advantageous allele to the next generation

4. as a result over many generations, the new allele increases in frequency in the population

one of the extremes has the selective advantage. Favours individuals in one direction from the mean
occurs when there is a change in the environment
modal trait changes

modal traits have selective advantage. Favours average individuals
occurs when there is no change in the environment
modal trait remains the same
standard deviation increases as individuals with extreme trait decrease