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More problems of genetic inheritance of a character. (Page 6)

Genetics problem 36

The ability to taste phenylthiocarbamide or PTC is determined by a dominant T allele, and the inability to taste it by the recessive t allele. If two heterozygous people who can taste phenylthiocarbamide have children, what genotypes and phenotypes will the offspring have?


Genetics problem 37

Some members of certain families have "woolly hair", similar to sheep's wool. All people who have woolly hair have at least one parent, who also has woolly hair. How is this hereditary character inherited?

Genetics problem 38

In cats, the allele that determines short hair is dominant over that of long hair. A short-haired male has children with a long-haired female. They have eight kittens, six of them short-haired and two long-haired.

Has this character appeared in kittens born in the expected proportion?

What proportion would be expected?

Genetics problem 39

The absence of molars in the human species is due to an autosomal dominant gene. A couple, both without molars, have a daughter with molars.

a) List the genotypes of all members of this family.

b) What is the probability that they will have another daughter with molars?

c) What is the proportion of heterozygotes?

Genetics problem 40

The black color of the skin of a mouse species depends on the dominant allele (B), and the white color of its recessive allele (b). If a black female has white-skinned offspring, what is the female's genotype? What genotypes and phenotypes could the male that crossed with her have? Reason for the answers.

Genetics problem 41

In humans, cystic fibrosis is a disease caused by the recessive allele of an autosomal gene with two alleles (A, normal allele; a, cystic fibrosis allele). In a couple in which the woman is heterozygous and the man has cystic fibrosis, it indicates for this gene the types and proportions of the woman's ovules and the man's sperm and the phenotypes and genotypes of the offspring. Reason for the answer. 

Genetica problem 42

In a certain species of rodents, black hair is determined by a dominant allele (A) and brown hair by a recessive allele (a). What type of cross should be made with a black-haired specimen in order to find out its genotype? Reason for the answer.

Genetics problem 43

How is it possible for a person to manifest a hereditary disease that neither of their parents shows? Could it be that the descendants of this person did not suffer from the disease? Reason the answers representing the diagrams of the possible crosses.

Genetics problem 44

Achondroplasia is an abnormality determined by a gene that gives rise to a type of dwarfism in the human species. A couple, both achondroplastic, have two children, one achondroplastic and one who is not. In light of the above, please say reasonably

a) whether achondroplasia is a dominant or recessive character

b) what is the genotype of each of the parents

c) what are the probabilities that the next offspring of the couple will not be achondroplastic or will be.

Genetics problem 45

Farsightedness is an inherited eye defect that prevents close objects from focusing properly. The inheritance of some types of hyperopia is due to a single autosomal gene with two alleles: H and h. A farsighted man and woman have a farsighted child and another with normal vision. From these data indicate:

a) if the hyperopia suffered by this family is a dominant or recessive character;

b) the genotypes of the parents and of the two children;

c) in the event that the hyperopic son had a girl with a woman with normal vision, what probability would that girl have of being hyperopic? In each case, reason the answers by making the necessary crosses.


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