Genes and Variations 16:1

1. How Common Is Genetic Variation? A. Genes –different forms of alleles that represent a trait or characteristic. Many organisms have several alleles for one trait. 1. Many organisms are heterozygous for many or all of their traits.

2. Variation and Gene Pools A. Variation Is an appearance or characteristic that makes an organism look unique or different from the rest. Gene pool – developed by interbreeding and contains all genes visible and invisible ones that can be inherited. 2. Relative Frequency - The number of times a gene appears in a gene pool compared with the number of times other alleles for the same gene occur. 3. Is often expressed in %.

3. Sources of Genetic Variation A. Mutation – any change is a sequences of DNA, during replication or chemicals in the environment. They can affect the organism or not. Just because it is a mutation does not mean it is necessarily bad for the organism.

B. Gene Shuffling – This occurs during the formation of gametes during Meiosis, in Anaphase I. This allows genetic variety in populations. With our 23 pairs of chromosomes, humans can produce 8.4 million different combinations of genes.

4. Single Gene and Polygenic Traits A. Single Gene – a trait that is controlled by a single gene or 2 alleles is called a single gene trait. Single gene trait on a human is widows peak. 1. Monohybrid Punnett square B. Polygenic – any trait that is controlled by two or more alleles. Height is an example of a poly trait. 1. Di-hybrid Punnett square