Exercises on dominance and recessiveness

You genesthey appear in somatic cells in pairs and may have dominance or recessiveness over their allele. This determines which characteristic will be expressed by a given pair.

This feature causes allele genes to be classified as homozygous and heterozygous.

We prepared a list of exercises on dominance and recessiveness so you can test your knowledge about the alleles!

You can consult the feedback and save this list in PDF at the end of the post!

Exercises – Dominance and recessiveness

1) (Fuvest-SP) A black cat (A) was crossed with two black cats (B and C). Crossing cat A with cat B produced 8 kittens, all black; crossing cat A with cat C produced 6 black and 2 yellow kittens. What does the analysis of these results allow us to conclude?

a) The color black is dominant; A and C are homozygous.
b) The black color is dominant; A and B are homozygous.
c) The black color is dominant; A and C are heterozygous.

d) The color black is recessive; A and C are homozygous.
e) The color black is recessive; B and C are heterozygous.

2) When studying the genetic makeup of an individual, we observed that some alleles are expressed when they are homozygous or heterozygous, producing the same phenotype. Mark the alternative that correctly indicates the name given to this allele.

a) Recessive allele.
b) Lethal allele.
c) Dominant allele.
d) Codominant allele.
e) Multiple allele.

3) (UFAL) In sheep, the production of black wool is due to the recessive allele p and that of white wool to the dominant allele P. From the crossing of two white animals, a black ram is produced, which is backcrossed with the parent ewe. The probability of having a white animal from this backcross is:

a) Zero
b) 1
c) ½
d) ¼
e) ¾

4) Albinism is a condition that only happens when an individual has two alleles that are unable to produce the active form of tyrosidase, an enzyme responsible for the conversion of tyrosine to DOPA-quinone and from this to melanin. When an allele is only manifested in homozygosis, we say that it is one:

a) recessive allele.
b) lethal allele.
c) dominant allele.
d) codominant allele.
e) multiple allele.

5) (Urca) In guinea pigs, a rodent from the Andes widely bred in captivity throughout the world, the short coat is conditioned by a dominant gene, and the long coat by a pair of recessive alleles. Smooth hair is conditioned by a dominant gene, and curly hair is conditioned by a pair of recessive genes. If a couple of guinea pigs that are heterozygous for the two traits involving the hair type are crossed with each other, what percentage of guinea pigs with the same phenotype as the parents can we expect?

a) 6%
b) 12%
c) 25%
d) 50%
e) 56%

6) (UFLA) The allele that manifests its phenotype in both homozygous and heterozygous individuals is called:

a) lethal.
b) epistatic.
c) recessive.
d) dominant.
e) turned on.

7) (UDESC) Consider that in a certain population in Hardy-Weinberg equilibrium there is a gene with two alleles in a dominance relation to each other. Knowing that the frequency of the recessive allele in this population is 0.3, the expected frequency of individuals with the dominant trait is:

a) 91%
b) 50%
c) 25%
d) 75%
e) 12.5%

8) When an allele only expresses a phenotype when it is in homozygosis, we say that it is an allele:

a) lethal.
b) dominant.
c) recessive.
d) codominant.
e) epistatic.

9) In some cases of autosomal recessive inheritance, normal parents produce children with certain disabilities. This case can be observed in albinism, for example, where it is possible to verify the existence of albino children whose parents produce melanin properly. Regarding these statements, mark the correct alternative.

a) Homozygous dominant parents can produce homozygous recessive offspring.
b) Homozygous recessive parents can produce heterozygous offspring.
c) Heterozygous parents can produce homozygous recessive offspring.
d) Homozygous recessive parents can produce homozygous dominant offspring.
e) Homozygous dominant parents can produce heterozygous offspring.

10) Analyze the following statements and mark the correct alternative regarding dominant and recessive alleles.

a) Dominant alleles are those that are expressed only in homozygosity.
b) A recessive allele is expressed only when given in a single dose.
c) Dominant alleles are expressed in homozygosity and heterozygosity.
d) Recessive alleles are always on non-homologous chromosomes.

feedback

1 — c
2 — c
3 — c
4 — the
5 — and

6 — d
7 — the
8 — c
9 — c
10 — c

Click here to save this list of exercises in PDF!

See too:

• List of exercises on pedigrees
• List of exercises on spermatogenesis
• List of exercises on the chemical composition of the cell