Guide to the practical teaching
of biology and genetics

Monohybridism

TASK 1:

In snapdragon plants (Antirrhinum maius), dominant homozygote has red flowers, recessive homozygote has white flowers and heterozygote has pink flowers.
1. Complete genotypes in P (parental), F₁ (first filial) and F₂ (second filial) generations. What is the phenotype and genotype ratio of F₁ and F₂ generations?
2. What type of inheritance does the observed trait show? (complete or incomplete dominance)

TASK 2:

Use χ² test to compare obtained phenotype ratio in F₂ generation (79 red, 170 pink and 95 white snapdragon plants) with expected ratio (see task 1). Table values are here.

TASK 3:

Color of pumpkin can be white or yellow. Dominant allele W determines white color, while recessive allele w determines yellow color.
1. After crossing of two white pumpkins, 3/4 of offspring were white and 1/4 of offspring were yellow. What are the genotypes of parents and offspring?
2. White phenotype of pumpkin can be encoded by two different genotypes. Which are they? How can you find the genotype of one particular white pumpkin?

TASK 4:

White pumpkin crossed with yellow one resulted in 327 white and 361 yellow offspring (see task 2).
1. What are the genotypes of parents and offspring?
2. How is this type of crossing called?
3. Compare obtained and expected ratios using χ² test (table values are here).

TASK 5:

Blue and brown color of eyes in humans is determined by two different alleles of one gene. In 337 families, the following data were found:

What color of eyes is dominant? Complete genotypes of parents and children.

TASK 6:

Two black female mice were crossed with two brown males. One female had 9 black and 7 brown offspring in several litters; the second female had 57 black offspring in several litters.
1. How is the coat color inherited in mice? What color is dominant and why? Explain.
2. What are the genotypes of parents and offspring from the aforementioned crossings?

TASK 7:

Leaves of cucumber can be palmate or flabellate (called ginkgo). After crossing of two plants (homozygote with palmate leaves and homozygote with flabellate leaves), all offspring were palmate.
1. What type of leaves is dominant (palmate or flabellate)?
2. What are genotype and phenotype ratios in F₂ and B₁ (back crossing = crossing of recessive homozygote and heterozygote) generations?

TASK 8:

In Andalusian strain of chicken, dominant allele B determines dark color of feather, while recessive allele b determines white color of feather. Heterozygote has bluish color of feather.

What will be the color of feather of offspring after crossing of bluish female with: a) dark colored fowl, b) bluish colored fowl, c) white fowl?