Unit 10: Pedigrees and Probability of Inheritance

Question 1

What are outsiders in a pedigree?

Answer 1

People who we’re unable to tell what their genotypes are by looking at the pedigree.

Question 2

What are the two outsider rules for dominant pedigrees?

Answer 2

Outsider rule for dominant pedigrees: affected outsiders are assumed to be heterozygotes. Unaffected (normal) outsiders are homozygous recessive

Question 3

What is outsider rules for recessive pedigrees?

Answer 3

Outsider rule for recessive pedigrees: unaffected (normal) outsiders are assumed to be homozygous dominant.

Question 4

What do pedigrees show?

Answer 4

Pedigrees show how traits are inherited across many generations.

Question 5

What is an X-linked Dominant trait?

Answer 5

1. Affected fathers will always pass the trait to all their daughters (since daughters inherit the father’s X chromosome), but never to their sons.
2. Affected daughters will pass trait to about half her offspring.

Question 6

What is an X-linked recessive trait?

Answer 6

Affected sons from affected mothers.

Question 7

What is Y-linked inheritance?

Answer 7

Y-linked traits are transmitted in an exclusively male-to-male
pattern.

Question 8

What is mitochondrial inheritance?

Answer 8

If a female has a mitochondrial trait, all of her offspring inherit it.