Chapter 17 Inheritance Exam Questions

Question 1

Explain what is meant by codominant alleles. (1)

Answer 1

When both alleles are expressed in the phenotype.

Question 2

In fruit flies, the genes for body colour and wing length are linked. Explain what this means (1)

Answer 2

The genes are on the same chromosome.

Question 3

Mutation is one cause of genetic variation in organisms. Give two other causes of genetic variation (2)

Answer 3

-crossing over
-independent segregation

Question 3

In genetic crosses, the observed phenotypic ratios obtained in the offspring are often not the same as the expected ratios.
Suggest two reasons why (2)

Answer 3

-Small sample size
- Linked genes

Question 4

What is meant by term phenotype? (2)

Answer 4

The characteristic expressed due to the genotype and environment

Question 5

What is the phenotypic ratio in a dihybrid cross if both parents are heterozygous?

Answer 5

9:3:3:1
UNLESS there is autosomal linkage or crossing over

Question 6

What is the ratio for autosomal linkage.

Answer 6

3:1