Pedigrees

How do you determine the probability of independent and mutually exclusive events? What are examples of each in pedigrees?

• independent - multiply odds; ex. probability child is AA (A from mom x A from father)

• mutually exclusive - add odds; ex. probability child has a dominant phenotype (AA or Aa)

What do affected and unaffected individuals look like in pedigrees?

• affected - black (can be dominant or recessive)

• unaffected - blank (can be dominant or recessive)

What are:

• autosomal recessive

• autosomal dominant

• x-linked recessive

• x-linked dominant traits?

• autosomal recessive - need aa to be affected, gene is on any chromosome except X/Y, affects males and females equally; Aa are carriers but unaffected

• autosomal dominant - Aa or AA to be affected, males and females affected equally, gene is on any chromosome except X/Y, unaffected don’t pass trait on

• x-linked recessive - gene on X-chromosome, females need 2 copies to be affected, males only need one; affects males more often than females, not passed father to son

• x-linked dominant - gene on X-chromsome, equal male/female affected, only one copy needed to be affected, all daughters of affected father are affected

What are the typical and atypical allele in pedigrees?

• typical allele - affected (can be dominant or recessive)

• atypical allele - unaffected allele

How does finding probability change between these 2 questions:

• if she has a son, what is the probability he’d be affected?

• What is the probability that she has an affected son?

• probability of affected

• probability of affected x probability of son (independent events)

What is a reciprocal cross?

pair of crosses where the phenotype of the male and female parents are reversed, designed to determine if a trait's inheritance is sex-linked or maternally influenced

What are characteristics of X-linked recessive inheritance?

• males more likely to be affected than females (only need one copy to be affected)

• no father to son transmission

• daughters of affected males are carriers

What are characteristics of X-linked dominant inheritance?

• equal male to female affected ratio

• daughter of affected fathers are affected

• appears in every generation

• sons don’t get trait from father

What do common and rare traits apply?

• common: outsiders can be hetero/homozygous for that trait

• rare: outsiders are homozygous for unaffected allele