Biology Exam 3 Material

Aneuploidy

Extra or missing chromosomes

Nullisomic

Lacking both homologs of a chromosome

Monosomic

Lacking one chromosome (2n-1)

Trisomic

One extra chromosome (2n+1)

Tetrasomic

2 extra chromosomes (2n +2)

Euploidy

Extra of fewer complete sets of chromosomes

Euploid

Normal complement of chromosomes (haploid, diploid)

Monoploid

One set of chromosomes

Polyploid

3 or more sets of chromosomes (triploid, tetraploid)

Polyploidization

Mechanism to help species adapt to changing conditions by changing the number of complete sets of chromosomes

Antipolyploid

Intra-sprecies polyploidization

Allopolyploid

Inter-species polyploidization

epigenetics

Heritable phenotype changes that do not involve alterations in the DNA sequence

Hardy Weinberg equilibrium

Useful models to estimate the allele and genotipyic frequencies of a hypothetical population that is independent of any forces of evolution.

5 Main forces of evolution

1. Finite population size

   1. Causes Genetic drift

2. Non-random mating

3. Mutation

4. Migration

5. Selection

Population

Sum of all individuals, characterized by their genotypes

Gene pool

Sum of all alleles carried in all (breeding) members of a population

Populations are characterized by ____

genotypic frequencies

Gene pools are characterized by ________

allele frequencies

Mutation

Any change in the genetic material

Mutation examples

• Single base

• Insertions and deletions

• Microsatelllite

• Chromosomal

Irreversible (one-way) mutations

Allele B mutates to b at a rate of μ per B allele per generation

Reversible (two way) Mutations

Rate at which the b allele mutations back to B is v

Ecology

Movement of individuals or populations from one area to another

Population Genetics

Movement of genes from one population to another

Genetic Drift

Random change in allele frequencies that occurs in populations, especially small ones

Fixation

Allele frequency goes to 100%

Extinction

Allele frequency goes to 0%

Buri (1956) Drosophila Expt

• Started with 107 populations with 16 flies, each with 0.5 frequency of a marker allele

• From each chose 16 random offspring each generation

• Repeated for 19 generations

Takeaway- showed random genetic drift in small populations

As population size N increases

• Generational fluctuations increase

• Variance between trials increase

• Time to fixation/extinction increases

Founder Effect

When a few individuals separate from a larger population and establish a new one that is isolated from the original

Population Bottleneck

When a large population of individuals die and later the population expands again

Effective population size

The number of equally reproductively able individuals that represent the gene pool being transmitted