Topic 7B: Evolution of Populations

what is the only source of new genes and new alleles

mutations

genetic ____ makes evolution possible

variation

what are point mutations

changes in one nucleotide base in a gene

what do chromosomal mutations do

delete, disrupt, duplicate, or rearrange many loci at once

most of the genetic variations with a population are due to the _____ recombination of ____ that already exist in a _____

sexual, alleles, population

what are the three mechanisms for shuffling of alleles

1. crossing over

2. independent assortment

3. fertilization

4. (mutation but very rare)

what is transformation

DNA from the environment can be taken into the bacteria and can make it its own

• assimilating external DNA

what is conjugation

• (horizontal gene transfer)

DNA in the plasmid in one bacteria is transferred to another through the conjugation tube (sex pilli)

what is transduction

• requires viruses

• viruses bind to bacteria and infect them

• virus injects DNA into bacteria

• Bacteria incorporate viral DNA into their genome

• Can transfer genes between bacteria

• Leads to genetic variation

what are the mechanisms for asexual variation

- transformation (uptake external RNA)
- transduction (incorporate viral DNA)
- horizontal gene transfer (conjugate tube)

what are population genetics

the study of how populations change genetically over time

what is a population

a group of individuals of the same species that live in the same area and interbreed, producing fertile offspring

what is a gene pool

all of the alleles at all loci in all the members of a population

if all members of a population are homozygous for the same allele, the allele is said to be ____

fixed

The Hardy-Weinberg equation can be used to test whether a ____ is ____

population, evolving

what are the five conditions for Hardy-Weinberg Equilibrium

1. No change in allele frequency due to mutation

2. Random mating

3. No natural selection

4. The popuation size must be extremely large (no genetic drift)

5. No gene flow (Emigration, immigration, transfer of pollen, etc.)

what is the Hardy-Weinberg principle used for

describe a population that is not evolving

what does the Hardy-Weinberg principle state

the frequencies of alleles and genes in a population’s gene pool will remain constant over the course of generations unless they are acted upon by other forces

what is the Hardy-Weinberg Equation

p² + 2pq + q²

• p = freq. of the dominant allele

• q = freq. of the recessive allele

• p + q = 1 (100% of all genotypes in the population)

• p² = AA

• q² = aa

• 2pq = Aa (Aa or aA)

• p² + 2pq + q² = 1 (100% of all genotypes in population)

if p and q remain the same…no evolution occurs

if p and q change, microevolution has occurred