Bio- Chapter 23

The three factors that cause allele frequencies are mutation, genetic variation, and sexual reproduction.

Discrete characters are either-or genes at a single locus with many alleles. Quantitative characters vary along a continuum and have two or more genes that affect one phenotypic character.

Average zygosity is the average percent of loci that are heterozygous. It is measured using gel electrophoresis.

Geographic variation is the difference in genetic composition of separate populations. It is analyzed using karyotypes.

Cline is a graded change in a character along a geographic axis.

Point mutations can be harmless 1) if they are in a noncoding region, 2) if they code for the same amino acid despite the change, or 3) if a change in the amino acid that gets coded doesn't affect gene expression.

Mutations occur once per one hundred thousand genes per generation. The short generation rate of viruses leads to a high rate of mutation.

Sexual reproduction leads to gene diversity through crossing over, independent assortment of chromosomes, and fertilization.

P²+2PQ+Q²=1 is the Hardy-Weinberg equation. P²= both dominant. 2PQ= heterozygous. Q²= both recessive.

The four conditions for the Hardy-Weinberg equation to work are: no mutations, no natural selection, no gene flow, random mating, and extreme population size.

The different types of selection are: directional (favors one phenotypical extreme), disruptive (favors both phenotypical extremes), and stabilizing (favors the middle).

Sexual selection: More likely to obtain mates. Sexual dimorphism: differences in the two sexes beyond the primary sexual characteristics. Intrasexual selection: selection within the same sex caused by competition. Intersexual selection: mate choice.

Frequency-dependent selection: fitness declines because a certain trait has become common.