Lecture 9/18 - E2

Question 1

What can alter the phenotype of an autosomal mutation?

Answer 1

Age or gender
Example: Chin hair requires the expression of B2 allele
Heterozygotes that are B1B2 - females are beardless while males have a beard

Question 2

Penetrance

Answer 2

The proportion of genotypically equivalent offspring that show the mutant phenotype

Question 3

Fully Penetrant Mutant Allele

Answer 3

The genotype = the phenotype where the phenotype is always predicted by the genotype

Question 4

Non-penetrant Mutant Allele

Answer 4

The genotype does not equal the phenotype, organism has the mutation by it doesn’t show as the mutant phenotype

Question 5

Incomplete Penetrance Mutant Allele

Answer 5

Genotype sometimes equals the phenotype where some offspring are mutant but others are WT

Question 6

What does 30% penetrance indicate?

Answer 6

that 30% of the offspring with the mmutant genotype have the utant phenotype while 70% show WT

Question 7

The hypothetical dominant autosomal gene (G) is needed for long legs in goats. The pygmy goat variety is gg. A gg x gg cross produced 5 offspring, 1 with long legs and 4 with short legs. What is the penetrance of the gg mutant phenotype?

Answer 7

4/5 = 80%

Question 8

Variable Expressivity

Answer 8

The degree to which symptoms of the same genetic condition vary between individuals with the same mutation.

Question 9

What is the difference between penetrance and variable expressivity?

Answer 9

Penetrance quantifies the number of affected individuals showing a disorder while varibale expressivity documents variation in the symptom features or severity.

Question 10

Pleiotropy

Answer 10

When a gene mutation impacts multiple different developmental pathways, behaviors, etc.

Question 11

Six individual twins heterozygotes for a dominant mutation that causes weak muscles, four are fully healthy and two have weak muscles. This disease pattern most likely reflects:
A) Pleiotropy
B) Simple Dominance
C) Incomplete Dominance
D) Incomplete Penetrance
E) Variable Expressivity

Answer 11

Numbers = penetrance

D) Incomplete penetrance