Test Cross

Concept Recap on:
Test cross
Multiple alleles
Sex determination
Continuous vs discontinuous variation
Gene mutation and chromosomal mutation

Multiple Choice

A single gene test cross is conducted to determine the genotype of a pea plant that shows the dominant phenotype for height (T = tall, t = short).

If all offspring of the cross show the dominant phenotype, then the genotype of the unknown parent is _______.

• TT

• Tt

• tT

• tt

Multiple Choice

You want to determine the pea color genotype of a pea plant with yellow peas. In this plant, yellow (Y) is dominant and green (y) is recessive. You conduct a test cross with your mystery pea plant.

The test cross results in 50% of the offspring possessing yellow peas and 50% of the offspring possessing green peas.

What is the genotype for pea color of the mystery parent?

• YY

• Yy

• yy

Open Ended

A man with type B blood marries a woman with type A blood. They have the first child with blood type O.

(i) What are the genotypes of the parents?

(ii) What is the probability of the second child having blood type AB?

(iii) What is the probability of having a son with blood type AB?

Multiple Choice

Humans have two types of sex chromosomes. Which are the two?

• A and B

• X and Z

• X and Y

• Y and Z

Multiple Select

Which of the following statementS explain the factors affecting sex determination in humans?

• Sex in humans is fixed before birth.

• Sex in humans is determined by genetic material carried in gametes.

• Sex in humans is determined by the environment of the mother.

• Climate affects the sex of human offspring.