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Two-character genetic inheritance (problems solved). (Page 10)

Genetics problem 69

A mouse with long gray hair is crossed with another mouse with long hair but white, is there any possibility that mice with short gray hair will be born? And with short white hair? If so, give reasons for your answer.
(Long hair, L, dominates over short hair, l; and gray hair, B, over white hair b).

Genetics problem 70

The black coat of Cocker Spaniels is governed by a dominant "B" allele and the color red by its recessive "b" allele. The uniform color pattern is governed by the dominant "S" allele and the speckled pattern by its recessive "s" allele. A male with uniform black hair mates with a female with red and mottled skin and they produce a litter of six puppies: 2 uniform black, 2 uniform red, 1 mottled black, and 1 mottled red. Determine the genotypes of the parents.

Genetics problem 71

In certain animal species, gray hair is dominant over white hair and curly hair over straight. An individual with straight white hair is crossed with another with curly gray hair, who has a white-haired father and a straight-haired mother.

a. Can they have children with straight gray hair? If yes, in what percentage?
b. Can they have children with curly white hair? If yes, in what percentage?

Genetics problem 72

Dark colored hair in men is dominant over red hair. The blue color of the eyes is due to a recessive gene with respect to its allele for the color brown. A man with brown eyes and dark hair married a woman with dark hair and blue eyes. They had two children, one with brown eyes and red hair and the other with blue eyes and dark hair. How are the genotypes of the children?

Genetics problem 73

In peppers, the green color (G) is dominant over the red (g), and the rounded shape (R) is dominant over the quadrangular (r).

a) What gametes will a diheterozygous round-shaped green pepper plant produce ?

b) What genotypes will the crossing of two of these diheterozygous plants produce?

Genetics problem 74

Suppose a certain species of rabbit in which black hair color dominates over white hair color and long ears dominate short ears.

What genotypes and phenotypes are expected from the cross between a black, long-eared, dihybrid rabbit with a white, short-eared rabbit?

Genetics problem 75

Short hair in rabbits is determined by a dominant allele (B) and long hair by its recessive allele (b). Hair color is determined by another gene with two alleles, so that individuals with a dominant genotype (N_) have black hair and those with a recessive genotype (nn) have brown hair. In crosses of dihybrid black short-haired rabbits with homozygous long-haired brown rabbits, what genotypic and phenotypic ratios can be expected in their progeny? Reason for the answer.

Genetics problem 76

Two pure lines of guinea pigs have been crossed, some with black hair (N) and smooth (r) and others with gray hair (n) and curly hair  (R). If the black and curly characters are dominant:

a) What is the genotype of the guinea pigs that are crossed and the genotype of the F1 generation?
b) If two guinea pigs of the F1 generation are crossed, indicate the genotypic and phenotypic percentages  of the F2.

Genetics problem 77

In Drosophila, the gray color of the body is determined by the dominant A allele, and  the black color by the recessive a. The wings of the normal type are determined by the dominant Vg  and the vestigial wings by the recessive vg. What will be the genotypic and phenotypic ratios  resulting from a cross between a homozygous gray-bodied double with vestigial wings and a heterozygous double  ? Give reasons for the answer.

Genetics problem 78

In a breed of cat, the gene that determines hair length has two alleles. A determines short hair is dominant over A, which determines long hair. Another gene determines hair color, where the B allele produces black color and is dominant over the b allele that determines reddish hair. The proportions of the offspring of a couple in which the male is reddish with long hair and the black female with short hair is as follows: 25% black and short hair; 25% short reddish hair; 25% long black hair; 25% long reddish hair. What is the mother's genotype? What are the genotypes of the offspring?