Inheritance: Unit 4, Topic 1

Question 1

What is Dominance?

Answer 1

There are three types of dominance:
- Complete, incomplete, and codominance

Complete dominance:
- individual with heterozygous genotype
- dominant allele shows up in offspring
- recessive allele gets covered up and doesn’t show
- one allele completely masks the other

Incomplete dominance:
- some heterozygous genotypes allow both alleles to partially show
- blending how they are expressed
- one allele doesn’t completely mask the other

Codominance:
- some heterozygous genotypes allow both alleles to be completely expressed at the same time (like spots or stripes)
- neither allele completely masks the other.

Question 2

What are the patterns of inheritance?

Answer 2

Autosomal Dominant:
- each affected person has an affected parent.
- It occurs in every generation
Autosomal Recessive:
- both parents of an affected person are carriers
- not typically seen in every generation

X-linked dominant:
- females are more frequently affected.
- can affect males and females in same generation if the mother is affected.
X-linked recessive:
- males are more frequently affected
- affected males often present in each generation

Question 3

What is polygenic inheritance?

Answer 3

• when one characteristic is controlled by two or more genes
• eye colour, skin colour, hair colour, height, weight, and blood type are determined polygenically