Genetics Problems Notes

Name______Per____

Genetics Problems II (Homework)

1. List the correct alleles for the traits for each.

Given: Black fur (B) is dominant over white fur (b) in rabbits.

Normal skin (N) is dominant over albinism (n) in humans.

1. _____ heterozygous black fur

1. _____ homozygous normal skin
2. _____ heterozygous normal skin
3. _____ homozygous white fur
4. _____ homozygous albinism
5. _____ homozygous black fur

B. Monohybrid Crosses: Use the symbols above to complete the following problems.

1. Cross a heterozygous normal skin man with a homozygous albino woman.

What are the genotypes of the mom and dad? _____ x _____

Show your work with a Punnett square:

What are the genotypes of the offspring? ______

What’s the ratio or percentage of each?______

What are the phenotypes of the offspring? ______

What’s the ratio or percentage of each? ______

1. Cross a homozygous black rabbit with a homozygous white rabbit.

What are the genotypes of the mom and dad rabbits? _____ x _____

Show your work with a Punnett square:

What are the genotypes of the offspring? ______

What’s the ratio or percentage of each?______

What are the phenotypes of the offspring? ______

What’s the ratio or percentage of each? ______

1. Cross a heterozygous normal skin man with a heterozygous normal skin female.

What are the genotypes of the mom and dad ? _____ x _____

Show your work with a Punnett square:

What are the genotypes of the offspring? ______

What’s the ratio or percentage of each?______

What are the phenotypes of the offspring? ______

What’s the ratio or percentage of each? ______

1. Use your own symbols for the following crosses.

1. Cross a heterozygous red flower with a homozygous recessive white flower.

The letter for red is _____. The letter for white is _____.

The genotypes of the parent flowers are _____ x _____

Show your work in a Punnett square:

What are the genotypes of the offspring? ______

What’s the ratio or percentage of each? ______

What are the phenotypes of the offspring? ______

What’s the ratio or percentage of each? ______

1. Cross a homozygous wire hair (dominant) dog with a homozygous recessive smooth hair texture dog.

The letter for wire hair is _____. The letter for smooth is _____.

The genotypes of the parent dogs are _____ x _____

Show your work in a Punnett square:

What are the genotypes of the offspring? ______

What’s the ratio or percentage of each? ______

What are the phenotypes of the offspring? ______

What’s the ratio or percentage of each? ______

Test cross – seeing the invisible

Scientists wanted to know how to tell if an organism showing the dominant phenotype was homozygous or heterozygous so they developed the test cross.

A test cross involves breeding (crossing) an organism whose genotype is recessive with a phenotypically dominant organism. Perform the following test crosses:

a) YY x yy

Genotypic ratio: ______

Phenotypic ratio: ______

b) Yy x yy

Genotypic ratio: ______

Phenotypic ratio: ______

What is the difference in the results of the two test crosses? ______

______

1