2A Pedigrees 10/15

What is a pedigree?

• first step toward mapping human genes

• chart of ancestors that shows line of descent or family history of a person

• means to track phenotypes in humans though generations (leading to genetic mapping(

What is the nomenclature of a pedigree?

• female = circle → filled in means affected

• male = square → filled in means affected

• heterozygotes = split shape

What do pedigrees highlight?

how traits (particular alleles) are inherited through generation

Phenotypes can be ____

“sex” linked, meaning gene is on X or Y

what does autosomal recessive look like?

• Both sexes equally affected

• Both sexes transmit to offspring

• Skips generations and is generally infrequent within the pedigree

• “autosomal” = not on the sex chromosome

eg of autosomal recessive inheritance

Sickle cell anemia

Beta thalassemia

Cystic fibrosis

Factor 13 deficiency

Fanconi anemia

Phenylketonuria

mutations in the CFTR gene cause mucus buildup

what are patterns of autosomal dominant inheritance?

• Both sexes equally affected

• Both sexes transmit to offspring

• No skipped generations

what are eg of autosomal dominant inheritance?

Achondroplasia

Von Willebrand disease

Marfan syndrome

Neurofibromatosis

Williams syndrome

Myotonic dystrophy

Huntington’s Disease

What does it mean if one is autosomal dominant?

Usually means that the affected allele produces a protein that is overactive. This trumps the normal allele.

What are patterns of X-linked recessive inheritance?

• males far more frequently affected than females

• no father to son inheritance bc women pass X chromosome to their children (men pass Y chromosome)

• women don’t get bc women have two X chromosomes → one can compensate for the other

What is going on genetically during X-linked recessive inheritance?

Since X and Y are not homologs, only one affected allele on the X causes the disease in males.

What are patterns of X-linked dominant inheritance?

• Females 2x more likely to be affected

• No father to son inheritance → bc inheriting the Y from their father

• 100% of daughters will inherit if father is affected

how can we verify inheritance patterns?

using pedigrees from diff families

What are patterns of Y-linked inheritance?

• ONLY males affected

• All sons from affected father will be affected

• Daughters will never inherit → only take Y chromosome from men (men and men)