Lecture 5

Question 0

What is penetrance and expressivity?

Answer 0

Penetrance - percentage who show the inherited characteristic in phenotype
Expressivity - degree to which an inherited characteristic is expressed

Question 1

What is multiple allelism?

Answer 1

Having more than 2 alleles ie. ABO blood group system

Question 2

What is polydactyly?

Answer 2

Having extra fingers or toes
Dominant but penetrance is about 90%
Degree of expression varies

Question 3

What is pleiotropism?

Answer 3

Where a single mutation can have multiple phenotypic effects

Question 4

What are lethal and sub-lethal alleles?

Answer 4

Lethal alleles - death before reproductive age

Sub-lethal alleles - death after reproductive age

Question 5

What is imprinting?

Answer 5

Most genes are not imprinted and are expressed identically, whether they come from father or mother
Some genes are imprinted - the gene from one parent can be switched off
- occurs in gamete formation
If a child inherits a dominant imprinted allele from one parent and a recessive allele from the other the child will show the recessive phenotype