The document discusses Mendelian genetics and how traits are inherited from one generation to the next. It explains that traits are transmitted through meiosis when haploid cells from each parent unite during fertilization. Individual traits are determined by alleles at gene loci, which can be dominant, recessive, or codominant. Punnett squares can be used to predict the distribution of traits in offspring based on the parents' genotypes. The document also describes Mendel's laws of segregation, independent assortment, and recombination that describe genetic inheritance.

1. Mechanisms of Evolution: Mendelian Genetics Anthropology 101 Hybrid Course

2. Mendelian Genetics The appearance of an individual is derived from the cell divisions we just described Traits are maintained in the organism through mitosis They are transmitted from parent to offspring through meiosis When haploid cells are united between couples to become diploid Each parent contributes exactly half their makeup to their offspring

3. Individual Genetics; :Concepts Traits are inherited through the chromosomes and their constituent genes The genetic composition of a trait is known as a genotype A phenotype is a trait of a genotype that is visible or otherwise observable and can be measured Homozygous traits are those with two identical alleles in a gene pair Heterozygous traits are those with two different alleles in a gene pair

4. Individual Genetics: When Genotypes Become Phenotypes A dominant allele is one whose trait appears in both homozygous heterozygous combination A recessive allele is one whose trait appears only in homozygous combination. A codominant allele is one whose trait reflects the genetic combination of two different alleles Punnett squares illustrate how these principles work

5. Case Study of Monogenic Trait: Tasters vs. Nontasters Most of us can taste the bitterness of Brussels sprouts This is the ability to taste phenylthiocarbamide (PTC) Tasters are dominant; nontasters are recessive A Punnett Square allows us to determine the proportion of tasters vs. nontasters of PTC This is a table that gives us a visual count of the allele for each trait.

6. PTC Tasters and Nontasters: Generation I Suppose one parent is a taster and the other is a nontaster in the first generation All the offspring (Generation II) will be tasters in the second generation, as shown in the next panel. To simplify, we use only a 2 X 2 table

7. Punnett Square of Tasters and Non-Tasters: Generation II t (nontaster) t (nontaster) T (taster) Tt Tt T (taster) Tt Tt

8. PHC Tasters and Nontasters: Generation II The second generation generate a new combination of phenotypes The proportion is now 1 homozygote for PTC tasters, 1 homozygote for nontasters, and 2 heterozygotes for tasters/nontasters.

9. Punnett Square of Tasters and Non-Tasters: Generation III T (tasters t (nontasters) T TT Tt t Tt tt

10. Codominant Genes Some alleles are codominant: one trait does not trump the other A species of flower, four-o’clocks, may come in red and white Their hybrids thus come in pink in Generation II In the Punnett Square, in Generation III, the proportion is 1:2:1 (one red, two pinks, and one white)

11. Mendel’s Laws: Law of Segregation Mendel found that there were three principles of inheritance resulting from the study of pea plants for seven characteristics. In so doing, he found that traits of the parent generation do not blend in those of their offspring. Rather, one gene for each trait is segregated from other genes for other traits. Segregation : Separation of alleles in the formation of gametes (sex cells)

12. Mendel’s Law: Law of Independent Assortment Independent Assortment: differing traits are inherited independently of each other (genes on separate chromosomes) For example whether a pea plant flower is violet or white is separated from smooth or wrinkled peas In other words, a white flowering plant can yield either a wrinkled or a smooth pea; so can a violet flowering plant So flower color is independent from smoothness of peas The PHC assortments in the Punnett Squares are another example of this law.

13. Mendel’s Laws: Law of Recombination Though independent, genes can recombined to allow further genetic variety In meiosis, some genes cross over, allowing even further variety.

14. Linkages Nevertheless, if alleles occur on the same chromosome, they will be inherited together. Sex-linked traits are one example: secondary characteristic are linked to the primary characteristics (organs of reproduction

15. Conclusion Genes are ultimately responsible for our traits Cells are maintained by cell division called mitosis Our traits are passed down from one generation to the next by meiosis Through meiosis, we can predict what traits will be passed down and in what proportion.