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Question 1
Why can siblings look different from each other?
Correct Answer:
They inherit different combinations of chromosomes and alleles from their parents
Explanation:
Genetic variation among siblings arises because each child receives a unique mix of chromosomes and gene variants from the parents. In sexual reproduction, each parent has two copies of every gene, but gametes carry only one copy. During meiosis, crossing over creates new combinations of alleles, and independent assortment shuffles which chromosome from each parent ends up in a gamete. When a sperm fertilizes an egg, the zygote ends up with a specific, unique combination of maternal and paternal alleles. With many genes involved, these differences across genes lead to different traits and appearances among siblings. Environmental factors can also influence how traits are expressed, adding even more variation. The other ideas don’t fit because siblings do not inherit identical genetic material (that would be true for identical twins, not typical siblings), they do not necessarily have the same phenotype, and they are not from different species.
Question 2
What is the genotype notation for a male affected by an X-linked recessive trait?
Correct Answer:
X^a Y
Explanation:
In X-linked recessive traits, males are hemizygous for the X chromosome, so the trait shows if the single X they inherit carries the recessive allele. Since the Y cannot carry a corresponding allele to mask it, the recessive allele on the X is enough to express the trait in the male. Therefore, an affected male’s genotype is X^a Y, with X^a representing the X chromosome that carries the recessive allele. If the male were unaffected, he would be X^A Y, where X^A has the dominant normal allele. For females, two copies are needed to be affected (X^a X^a), while a female carrier would be X^A X^a.
Question 3
Example of a homozygous dominant genotype?
Correct Answer:
AA.
Explanation:
Homozygous dominant means having two copies of the dominant allele. In this context, the dominant allele is represented by A, so two dominant alleles appear as AA. This pair on the two homologous chromosomes makes the genotype homozygous (two identical alleles) and dominant (both alleles are the same and both are the dominant version). For contrast, aa is two recessive alleles (homozygous recessive), and aA (or Aa) is heterozygous, with one dominant and one recessive allele. A heterozygous genotype can still express the dominant trait, but it is not homozygous dominant because the alleles are not both dominant. Hence, the example that shows two dominant alleles is AA.
Question 4
What does it mean that males are hemizygous for X-linked genes?
Correct Answer:
They have only one X chromosome, so one allele determines the trait
Explanation:
Males are hemizygous for X-linked genes because they have only one X chromosome, so for each gene located on X there is just one allele present. That single allele directly influences the trait, since there isn’t a second X chromosome to provide a second allele that could mask it. The Y chromosome doesn’t carry most of the X-linked genes, so it doesn’t offer a compensating allele for those loci. This is why X-linked recessive conditions tend to show up in males more often: a male needs only one recessive allele on his single X to express the trait, whereas females would need two copies. In females, having two X chromosomes means one good copy can often mask a problematic allele, or the expression can be more complex due to mechanisms like X-inactivation.
Question 5
Number of chromosomes inherited from each parent?
Correct Answer:
23 from the mother and 23 from the father.
Explanation:
Humans have 23 pairs of chromosomes in most cells, totaling 46. Each parent contributes one chromosome to every pair through their gametes. Gametes are haploid, containing 23 chromosomes. When a sperm and egg fuse, the resulting zygote has 46 chromosomes: 23 from the mother and 23 from the father. So the number inherited from each parent is 23.
Question 1
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Prepare with the CP Biology – Inheritance Practice Test practice quiz. This question bank includes 10 questions covering genotype, homozygous, parent, x-linked, and recessive. Use it to review important concepts, identify knowledge gaps, and build confidence for the related exam, course, or assessment.

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CP Biology – Inheritance Practice Test

This practice set contains 10 questions from the matching question bank and focuses on genotype, homozygous, parent, x-linked, and recessive. Work through each question carefully, review the provided solutions, and revisit topics that need more study before your next attempt.

This is an independent study resource intended for practice and review; it is not an official examination or an endorsement by any organization named in the title.

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