Free Mendel's Laws of Inheritance MCQs with Answers
130 Mendel's Laws of Inheritance MCQs from Biology, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Mendelian inheritance explains how alleles separate into gametes and assort during reproduction, producing predictable genotype and phenotype ratios. Questions cover dominance, recessiveness, homozygous and heterozygous conditions, the laws of segregation and independent assortment, monohybrid and dihybrid crosses, test crosses and the limits caused by linked genes.
Last updated
130 questions · page 2 of 7
- A. two sister chromatids of the same chromosome
- B. any two chromatids chosen at random
- C. the two strands of one DNA molecule
- D. non sister chromatids of homologous chromosomes
Explanation: Exchange between non sister chromatids of homologues shuffles maternal and paternal alleles, creating recombinant gametes.
Correct answer: non sister chromatids of homologous chromosomes22. The visible cross shaped points at which homologous chromatids have exchanged segments are called
- A. chiasmata
- B. centromeres
- C. kinetochores
- D. telomeres
Explanation: Chiasmata can be seen under the microscope in prophase one and mark where crossing over has occurred.
Correct answer: chiasmata- A. micrometres
- B. map units, or centiMorgans
- C. nanometres
- D. base pairs per gamete
Explanation: One map unit, one centiMorgan, equals one per cent recombination between two genes.
Correct answer: map units, or centiMorgans- A. no recombination at all
- B. complete linkage in every meiosis
- C. a higher recombination frequency than genes lying close together
- D. fewer crossing overs than genes lying close together
Explanation: The longer the stretch of chromosome between two genes, the more likely a crossover will fall between them, so distant genes recombine…
Correct answer: a higher recombination frequency than genes lying close together25. The chromosomal basis of linkage was worked out mainly through breeding experiments on Drosophila by
- A. Gregor Mendel
- B. Jean Baptiste Lamarck
- C. James Watson
- D. Thomas Hunt Morgan
Explanation: Morgan showed that certain Drosophila characters were inherited together and tied to the sex chromosomes, founding chromosome mapping.
Correct answer: Thomas Hunt Morgan- A. parental combinations of characters
- B. equal numbers of all four combinations
- C. recombinant combinations only
- D. non viable zygotes
Explanation: Because linked genes usually travel together, parental combinations outnumber recombinants, and the size of the minority reveals how far…
Correct answer: parental combinations of characters- A. 46
- B. 23
- C. 22
- D. 44
Explanation: One linkage group corresponds to each kind of chromosome in the haploid set, so humans have 23.
Correct answer: 23- A. 25 per cent
- B. 40 per cent
- C. 50 per cent
- D. 100 per cent
Explanation: Once genes are far enough apart that a crossover happens between them in every meiosis, half the gametes are recombinant, the same figure…
Correct answer: 50 per cent- A. autosomal
- B. Y linked
- C. mitochondrial
- D. X linked
Explanation: The X chromosome carries many genes unrelated to sex, and their inheritance is distinctive because males have only one copy.
Correct answer: X linked30. A male expresses an X linked recessive trait whenever he inherits one recessive allele because he
- A. has only one X chromosome
- B. has two Y chromosomes
- C. inactivates the normal allele
- D. lacks the gene altogether
Explanation: With no second X to supply a dominant allele, the single recessive allele has nothing to mask it, a state called hemizygosity.
Correct answer: has only one X chromosome- A. None
- B. Half
- C. A quarter
- D. All of them
Explanation: The woman must be a carrier since she inherited her affected father's X.
Correct answer: Half- A. was cured by royal physicians
- B. is common in every royal family
- C. was traced through the descendants of Queen Victoria
- D. was first described by a king
Explanation: Victoria carried the allele and passed it into the royal houses of Russia and Spain, producing affected princes across Europe.
Correct answer: was traced through the descendants of Queen Victoria- A. from mother to sons
- B. from father to all his sons
- C. equally to sons and daughters
- D. to daughters only
Explanation: Only males carry a Y chromosome, and a father passes it to every son and no daughter, so Y linked traits run strictly down the male line.
Correct answer: to daughters only- A. Red green colour blindness
- B. Sickle cell anaemia
- C. Down syndrome
- D. Albinism
Explanation: The genes for red and green pigments lie on the X chromosome, so colour blindness follows the X linked pattern.
Correct answer: Red green colour blindness- A. a man suffering from the disease
- B. a heterozygous woman with one normal and one haemophilia allele
- C. a homozygous normal woman
- D. a person with an extra chromosome
Explanation: A carrier holds the recessive allele without symptoms because the normal allele on her other X is enough for clotting.
Correct answer: a heterozygous woman with one normal and one haemophilia allele- A. zero
- B. one quarter
- C. one half
- D. certain
Explanation: The woman inherited her haemophiliac father's X, making her a carrier. She passes that X to half her sons, who will be affected, and the…
Correct answer: one half37. In the cells of a female mammal, one of the two X chromosomes condenses into a dense body called the
- A. centromere
- B. nucleolus
- C. chiasma
- D. Barr body
Explanation: The inactivated X, or Barr body, equalises the gene dose between XX females and XY males.
Correct answer: Barr body- A. Alleles separate during gamete formation
- B. Different genes assort independently
- C. Dominant alleles always mask recessive
- D. Genes are on chromosomes
Explanation: The law of segregation states that allele pairs separate during gamete formation, so each gamete carries one allele.
Correct answer: Alleles separate during gamete formation- A. Only dominant phenotype
- B. Only recessive phenotype
- C. Intermediate phenotype
- D. Both phenotypes expressed
Explanation: In incomplete dominance, the heterozygote shows an intermediate phenotype, e.g., pink flowers from red and white parents.
Correct answer: Intermediate phenotype- A. Heterozygote frequency
- B. Homozygous dominant frequency
- C. Homozygous recessive frequency
- D. Total alleles
Explanation: p² = frequency of homozygous dominant (AA), 2pq = heterozygous (Aa), q² = homozygous recessive (aa).
Correct answer: Homozygous dominant frequency