Bio 101 Sequencing Our Genome: Background

How can a black female dog have yellow, brown, and black puppies?

A Simple Cross: Mendel’s Peas

Mendel’s explanation for the flow of genes in matings

Mendel’s experimental test

Two genes…

What would a test cross for two genes look like?

YyRr x yyrr | YR Yr yR yr | yr | YyRy Yyrr yyRr yyrr 4 : 4 : 4 : 4, OR 1 : 1 : 1 : 1

Two genes are needed for a black female dog to have three colors of puppies

Pedigrees trace genes in families

A vertical pattern of inheritance indicates a rare dominant trait. Huntington’s disease: A rare dominant trait (“vertical pattern”) Assign the genotypes by working backward through the pedigree 1.All affected individuals have an affected parent. 2.About ½ of all children from an affected parent are affected.

2-12 Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display A horizontal pattern of inheritance indicates a rare recessive trait. Cystic fibrosis: a recessive condition (“horizontal pattern”) 1.Unaffected parents can produce affected children. 2.About ¼ of children are affected in families with the trait. 3.“Consanguinous” marriages may be involved. 4.Heterozygotes are called “carriers.” 5.All of the children of affected individuals must carry (or express) the trait. Fig.2.22

CQ#1: What is this pedigree telling us? personal genetics education project

Deciphering a Pedigree personal genetics education project DadMom Son (unaffected) Example: A family where a trait appears in 2 out of 3 children Twin son (affected) Twin daughter (affected)

Short applications A family has one child with cystic fibrosis. What is the probability that the next child will also have it? Be a carrier? If a man with sickle-cell disease (recessive) marries a normal woman, what is the probability that their first child will have the disease? BRCA1 mutations are associated with increased cancer rates on both men and women. What is the probability that the first child of a woman with a BRCA1 mutation (dominant) will have an increased probability of cancer?

personal genetics education project Maria age 60 breast cancer MalcolmVanessa AngelaAshleyEmily Steven XX Chris CQ#2 – What Can We Learn From This Pedigree?

What if we cannot SEE differences in DNA? Coat color, pea color, Huntington’s disease, sickle cell anemia, and cystic fibrosis can be tracked in famiies because the genes create visible changes. BRCA-1 and most other genes either: Do not create a visible genotype, or The genotype appears too late to be useful for diagnosis or treatment. HOW CAN WE TRACE IMPORTANT GENES IF WE CANNOT SEE THEM?

personal genetics education project Maria age 60 breast cancer MalcolmVanessa AngelaAshleyEmily Steven XX Chris CQ#2 – What We Learn From Genetic Screening Ages 22-37