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3.5.2.3. More two-character genetic inheritance solved problems 4

Two-character genetic inheritance (problems solved). (Page 12)

Genetics problem 89

In an animal species, the allele that determines gray is dominant over that of white and the allele that determines curly hair over that of straight hair. A gray individual, whose father has white hair and the mother is curly, is crossed with another with straight white hair.

Represent the necessary crosses in a table.

Can they have smooth and gray children? If so, what percentage?

Can they have children with curly hair? If so, what percentage? Reason for the answers.

Genetics problem 90

A dog breeder crosses a black-haired, brown-eyed male with a brindle-haired, yellow-eyed female of the  same breed and they have a litter of 7 black brown-eyed puppies. Answer the following questions using,  as appropriate, the letters A / a for alleles of hair color and B / b for alleles of eye color:

a) Indicate what the parental and F1 genotypes will be like and give reasons for the dominant alleles for each trait  (1 point).

b) Indicate the genotypic and phenotypic proportions of the cross of two F1 dogs (1 point).

Genetics problem 91

Myopia is due to a dominant gene, as is the Rh+ phenotype. A woman with normal Rh+ vision, the daughter of an Rh- man, has offspring with a heterozygous and Rh- myopic male.
SUGGESTED NOMENCLATURE:

M, Myopia; m, normal vision; R, Rh+; r, Rh

a. Indicate the expected genotypes of the couple's children.
b. What will be the phenotypes of the couple's children.

Genetics problem 92

The red color of the tomato pulp depends on the presence of a dominant factor (R) over its recessive allele (r) for yellow. The normal size of the plant is due to a dominant gene (N) over the small size (n). A plant with red pulp and normal size is crossed with another yellow and normal one and the following are obtained: 30 normal red plants, 31 normal yellow ones, 9 small red ones and 10 small yellow ones.

a) What are the genotypes of the plants that are crossed? Check the result by crossing.

b) What are the genotypes of the offspring?

c) What would be the phenotypic proportions that you would expect if you crossed the heterozygote for both traits with a small yellow plant? What is the name of this type of cross?

d) Indicates the phenotypic proportions that you would expect from the crossing of two heterozygous plants for both traits. (2 points)

Genetics problem 93

The large spike (G) in an ancestral wheat species is dominant over the small spike, and the orange basal leaf (A) dominates over the green one. An innovative farmer from Rioja Baja crossed a plant with a large spike and orange leaf with another with a large spike, but with a green leaf. He obtained two wheat plants, one with a large spike and a green basal leaf and the other with an orange leaf and a small spike. Reasonably indicate the genotypes of the parents and children. (1 point)

Genetics problem 94

The color of the tomato pulp and the size of the plant depend on two genes that segregate independently. The red color of the tomato pulp depends on the presence of the R factor, which is dominant over its r allele for yellow. Dwarfism in the plant is due to a recessive gene d. Two homozygous varieties are available for crossing, one with a yellow pulp and normal size and the other with a red pulp and dwarf bearing.

a) Make a scheme that shows the previous cross indicating the respective phenotypes and genotypes of both the parents and their descendants in F1. (Maximum score 1 point)

b) Obtain the F2 and explain if it could be obtained in it and with what frequencies: (Maximum score 1 point)

- A homozygous variety with red flesh and normal size.

- A variety of yellow flesh and dwarf bearing.

Genetics problem 95

The black coat in Cocker spaniels is governed by a dominant allele (R) and the color red by its recessive allele (r). The uniform color pattern is controlled by the dominant allele (M) and the mottling is caused by the recessive (m). A male with black, uniform hair mates with a female with mottled red fur and they have a litter of six puppies: two uniform blacks, two uniform reds, one spotted black, and one spotted red.

a. Determine the genotype of all dogs (parents and their possible offspring).
b. If a breeder crosses these two parent dogs, what proportion would be expected to have homozygous puppies for the two traits?

Genetics problem 96

Aniridia (a type of inherited blindness) in humans is due to a dominant allele. Migraine is also due to a dominant allele. An individual who suffered from aniridia, but not migraine, and whose mother was not blind, marries a woman who was not blind and who suffered from migraine, but whose mother did not suffer from it.

SUGGESTED NOMENCLATURE: A, Aniridia (blindness); a, normal vision; J, migraine; j, no headache.

a. List the genotypes of the pair. Justify your answers.
b. Indicate the proportions of the genotypes and phenotypes expected in the offspring

Genetics problem 97

The red color of the tomato pulp depends on the presence of a dominant R factor over its r allele for yellow. the normal size of the plant is due to a dominant N gene over the dwarf size n. A plant with red pulp and normal size is crossed with another yellow and normal one, and the following are obtained: 30 normal red plants, 31 normal yellow, 9 dwarf red and 10 dwarf yellow. What are the genotypes of the plants that are crossed? Check the result by crossing.

Genetics problem 98

The white color of certain herbivores is an autosomal recessive trait and the split hoof is an X-linked recessive trait. A white male with the entire hoof is crossed with a dark colored female whose father was white and split-hoofed, and whose mother was split-hoofed. Determine the genotypes of the animals that are crossed and the genotype and phenotypic frequencies of their offspring. (Use N and n for the color and E and e for the hoof shape)