1. Module II Mendelian Genetics & Probability Theory

2. GENETICS Genetics is the study of heredity and variation in organisms Genes are the hereditary units transmitted from generation to the next Genes reside in the long molecules of deoxyribonucleic acid (DNA) that exists within the cell DNA, in conjunction with a protein matrix forms nucleoprotein and becomes organized into structures called chromosomes that are found in the nucleus of the cell

3. ALLELES Mutation is a change in some part of the DNA The result of a mutation is a change a character or trait of the individual Through a mutation, a gene may be changed into two or more alternative forms called alleles Homologous chromosomes are genetically similar

4. MENDEL’S LAWS Law of segregation: If a parent contains 2 alleles of a trait, only 1 is transmitted through a gamete to the offspring Law of independent assortment: Segregation of one gene pair occurs independently of any other gene pair

5. Overview/Review of Basic Genetics Genetic material (DNA) is stored within structures called chromosomes. In sexually reproducing organisms (e.g. mammals and birds), an individual has two copies of each type of chromosome. Every species has a specific number of chromosomes (in humans there are 23 pairs of chromosomes = 46 total).

6. Genes (sequences of DNA which encode proteins) are found on chromosomes. Overview/Review of Basic Genetics Different Genes Each chromosome in a pair has the same genes in the same order. However, specific genes can be variable and the two chromsomes may not have the same gene variant.

7. Variants of a specific gene are known as alleles. Example: There is a gene in humans that controls basic eye color. There are two alleles: Blue (b) and Brown (B). The genotype of an individual is the set of alleles the individual has. Question: What are the possible genotypes for eye color? Answer:BB or Bb or bb Overview/Review of Basic Genetics

8. The phenotype of an individual is the physical characteristic formed by their specific alleles. Example: An individual with the brown alleles (BB) has a brown eyed phenotype. An individual with two blue alleles (bb) has a blue eyed phenotype. Question: Does an individual with 1 brown and 1 blue allele (Bb) have one brown eye and one blue eye? Answer: No. The brown allele is dominant over the blue allele (which is recessive). An individual with both alleles (heterozygous) has the phenotype of the dominant allele. Thus the Bb genotype = Brown phenotype. Overview/Review of Basic Genetics

9. Another example: Many plants can have flowers of different colors. Overview/Review of Basic Genetics Bougainvillea Snap Dragons

10. Bougainvillea on Campus

11. In many plants, flower color is controlled by a single gene. There are alleles for Red (R) and White (W) and sometimes other colors (e.g., yellow). A plant with an RR genotype has a red phenotype. A plant with a WW genotype has a white phenotype. A plant with an RW genotype has a pink phenotype. Neither R nor W are dominant. The are called co-dominant and the observed phenotype of a heterozygote is in between the phenotype of either homozygote. Overview/Review of Basic Genetics

12. Question: Can you predict phenotype from genotype? Answer: Yes. For eye color we know that BB and Bb are always brown and bb is always blue. Question: Can you predict genotype from phenotype? Answer: No. While we know a blue eyed person must have a bb genotype, a brown eyed person could have either Bb or BB. All we know for sure is they have at least 1 B. Overview/Review of Basic Genetics

13. An individual’s chromosomes are inherited from their parents. One from the father and one from the mother. When an individual has children, half of its chromosomes (one from each chromosome pair) will go into the child. The process by which a specific chromosome (and therefore specific alleles) goes into a child is random. What does any of this have to do with math?

14. Pretend you are going to breed a pair of plants with pink flowers. Question: What are the phenotypes of these plants? What are the genotypes? Answer: Phenotypes are both pink. Genotypes are both RW. Questions: What are the possible genotypes and phenotypes of the offspring? What is the probability of getting these genotypes and phenotypes? Answer: You may know the answer, but do you know the mathematics behind it… What does any of this have to do with math?