2. Mendel's Laws of Inheritance

Black skin color is dominant to pink skin color in pigs. Two heterozygous black pigs are crossed.

What is the probability that their offspring will have pink skin?

A black and white rabbit were mated. All F₁ offspring were black, and the F₂ offspring is made up of approximately ¾ black and ¼ white rabbits. 

• Draw out two Punnet squares detailing both matings.
• Supposed two white F₂ offspring were mated. What would be the phenotype and genotype of the F₃ offspring? 

Green scales (G) in a particular species of fish is dominant over blue scales (g). The following crosses are carried out, producing the progeny shown. Write out all possible genotypes of the parents in each cross.

Which of the following offspring ratios is expected from a Mendelian heterozygous cross examining one gene?

Human albinism is a simple recessive trait. Determine the genotypes of the parents for each offspring combination 

i. A wild-type male and albino female have 6 wild-type children 

Human albinism is a simple recessive trait. Determine the genotypes of the parents for each offspring combination

ii. A wild-type male and albino female have 8 children, 4 wild-type, and four albino 

Compare and contrast the following terms:

Monohybrid cross and Test cross

For the cross BB×Bb, what is the expected genotype ratio? What is the expected phenotype ratio?

A plant may have green, white, or green-and-white (variegated) leaves on its branches, owing to a mutation in the chloroplast that prevents color from developing. Predict the results of the following crosses:

  Ovule Source        Pollen Source

(a) Green branch    x  White branch

(b) White branch     x  Green branch

(c) Variegated branch x  Green branch

(d) Green branch    x  Variegated branch

In a type of parakeet known as a "budgie," feather color is controlled by two genes. A yellow pigment is synthesized under the control of a dominant allele Y. Budgies that are homozygous for the recessive y allele do not synthesize yellow pigment. At an independently assorting gene, the dominant allele B directs synthesis of a blue pigment. Recessive homozygotes with the bb genotype do not produce blue pigment. Budgies that produce both yellow and blue pigments have green feathers; those that produce only yellow pigment or only blue pigment have yellow or blue feathers, respectively; and budgies that produce neither pigment are white (albino).

c. What are the genotype(s) and phenotype(s) of the F₁ progeny of the cross described in part (b)?

Discuss how Mendel's monohybrid results served as the basis for all but one of his postulates. Which postulate was not based on these results? Why?

In a type of parakeet known as a "budgie," feather color is controlled by two genes. A yellow pigment is synthesized under the control of a dominant allele Y. Budgies that are homozygous for the recessive y allele do not synthesize yellow pigment. At an independently assorting gene, the dominant allele B directs synthesis of a blue pigment. Recessive homozygotes with the bb genotype do not produce blue pigment. Budgies that produce both yellow and blue pigments have green feathers; those that produce only yellow pigment or only blue pigment have yellow or blue feathers, respectively; and budgies that produce neither pigment are white (albino).

e. The cross of a green budgie and a yellow budgie produces offspring that are 12 green, 4 blue, 13 yellow, and 3 albino. What are the genotypes of the parents?

In a type of parakeet known as a "budgie," feather color is controlled by two genes. A yellow pigment is synthesized under the control of a dominant allele Y. Budgies that are homozygous for the recessive y allele do not synthesize yellow pigment. At an independently assorting gene, the dominant allele B directs synthesis of a blue pigment. Recessive homozygotes with the bb genotype do not produce blue pigment. Budgies that produce both yellow and blue pigments have green feathers; those that produce only yellow pigment or only blue pigment have yellow or blue feathers, respectively; and budgies that produce neither pigment are white (albino).

d. If F₁ males and females are mated, what phenotypes are expected in the F₂, and in what proportions?

In a type of parakeet known as a "budgie," feather color is controlled by two genes. A yellow pigment is synthesized under the control of a dominant allele Y. Budgies that are homozygous for the recessive y allele do not synthesize yellow pigment. At an independently assorting gene, the dominant allele B directs synthesis of a blue pigment. Recessive homozygotes with the bb genotype do not produce blue pigment. Budgies that produce both yellow and blue pigments have green feathers; those that produce only yellow pigment or only blue pigment have yellow or blue feathers, respectively; and budgies that produce neither pigment are white (albino).

b. A cross is made between a pure-breeding green budgie and a pure-breeding albino budgie. What are the genotypes of the parent birds?