The Role of Genes in Variation Darwins Difficulty

The Role of Genes in Variation

Darwin’s Difficulty ► No one knew how genetics worked during the 1800’s. ► Gregor Mendel was completing his work in genetics, but no one recognized the importance.

How Genetics Supports Evolution ► We can explain how traits are passed from parent to offspring. ► We can also explain how change occurs to those traits on the molecular level.

Genetics Vocabulary Refresher ► Alleles – different forms of the same gene. ► Population-all members of the same species who can breed in a given area. ► Trait – Physical characteristics that change from organism to organism

Genetics Vocabulary Refresher ► Gene pool – all genes, including all the different alleles, in a population. ► Relative frequency- how often one allele appears in a population compared to other alleles.

What is Evolution on the Genetic Level? ► Evolution on the genetic level is any change in relative frequency of alleles in a population.

How does genetic variation occur? ► Mutations – changes in a sequence of DNA that creates a new allele. § Most mutations cause no change in the organism’s traits. § Some create traits that hurt the organism. § Others create beneficial traits.

How does genetic variation occur? ► Gene shuffling- Sexual reproduction causes new combinations of genes in offspring. § Causes genetic variation at the organism level. § Does not change the frequency of the gene in the gene pool.

Single-Gene Traits ► Any trait that is controlled by a single gene that has two traits. § § Widow’s peak hairline Albinism Dimples Freckles ► Shows two character states.

Polygenic Traits ► Controlled by two or more genes with more than two alleles § § Hair color Eye color Skin color Height ► Shows many character states.