Free X-linked Recessive Inheritance MCQs with Answers
45 X-linked Recessive 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.
X-linked recessive inheritance involves genes on the X chromosome, so males express a recessive allele with no corresponding allele on their single X chromosome, while females may be carriers. Pedigrees cover haemophilia and red-green colour blindness, including carrier mothers, affected sons and the absence of father-to-son transmission.
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- A. a man has only one X chromosome, so a single recessive allele is expressed
- B. the gene lies on the Y chromosome
- C. the allele is dominant in men and recessive in women
- D. women lose the allele during meiosis
Explanation: The gene is on the X chromosome and a man is hemizygous, so there is no second copy that could mask a defective allele.
Correct answer: a man has only one X chromosome, so a single recessive allele is expressed- A. 0
- B. one in four
- C. one in two
- D. certain
Explanation: A son takes his single X from his mother, and half of her X chromosomes carry the defective allele, so half the sons are colour blind.
Correct answer: one in two- A. clotting factor VIII
- B. vitamin K
- C. platelets
- D. haemoglobin
Explanation: The X linked recessive gene codes for antihaemophilic factor VIII, and without it the clotting cascade stalls, so even a small injury…
Correct answer: clotting factor VIII- A. her mother alone is colour blind
- B. her father alone is colour blind
- C. her father is colour blind and her mother is at least a carrier
- D. neither parent carries the allele
Explanation: A girl has two X chromosomes and needs the recessive allele on both, one from each parent.
Correct answer: her father is colour blind and her mother is at least a carrier- A. the ovum, which may carry either an X or a Y chromosome
- B. the hormones of the mother during pregnancy
- C. the total number of chromosomes in the zygote
- D. the sperm, which carries either an X or a Y chromosome
Explanation: The mother is XX and so every ovum carries an X, while the father is XY and produces X bearing and Y bearing sperm in equal numbers, so it…
Correct answer: the sperm, which carries either an X or a Y chromosome6. In X linked recessive inheritance, the criss cross pattern means that a trait typically passes from
- A. father to son directly
- B. mother to daughter only
- C. father to every one of his sons
- D. an affected man to his grandsons through his carrier daughters
Explanation: An affected father gives his X, and therefore the allele, to all of his daughters, who become carriers, and half of their sons then…
Correct answer: an affected man to his grandsons through his carrier daughters- A. Autosomal dominant
- B. Autosomal recessive
- C. X-linked recessive
- D. Y-linked
Explanation: Haemophilia is an X-linked recessive disorder affecting blood clotting, more common in males.
Correct answer: X-linked recessive- A. Male with the disorder
- B. Female with one affected X
- C. Female with both X affected
- D. Male without the disorder
Explanation: Carrier females are heterozygous (XAXa) and phenotypically normal but can pass the allele to offspring.
Correct answer: Female with one affected X- A. The mother is a carrier and the father is normal
- B. The mother is hemophiliac and the father is normal
- C. The mother is carrier and the father is hemophiliac
- D. Both are normal
Explanation: A girl has two X chromosomes and needs the recessive allele on both, one from each parent, so the father must be haemophiliac himself and…
Correct answer: The mother is carrier and the father is hemophiliac- A. 0%
- B. 25%
- C. 50%
- D. 75%
Explanation: A colour blind mother carries the defective allele on both her X chromosomes, and a son receives his only X from her, so every son must be…
Correct answer: 0%- A. XY
- B. XX
- C. XXY
- D. XXX
Explanation: In the usual human chromosome pattern, females have two X sex chromosomes, written XX, while males have XY.
Correct answer: XX- A. Carrier mother and a colour blind father
- B. Carrier mother and an unaffected father
- C. Colour blind mother and an unaffected father
- D. Unaffected, non-carrier mother and a colour blind father
Explanation: The correct answer is a carrier mother and a color blind father. A carrier mother has one normal X chromosome and one affected X…
Correct answer: Carrier mother and a colour blind father- A. Protenor bugs
- B. Grasshoppers
- C. Butterflies
- D. Fruit flies
Explanation: The correct answer is butterflies. In the ZW sex-determination system, which is observed in butterflies, moths, and birds, the female is…
Correct answer: Butterflies- A. Option A
- B. Option B
- C. Option C
- D. Option D
Explanation: In the cross mother should be XX, father should be XY and son should be XY. Option D gives the correct representations.
Correct answer: Option D- A. Mother is carrier, father is normal
- B. Mother is hemophiliac, father is normal
- C. Mother is carrier, father is hemophiliac
- D. Mother is normal, father is hemophiliac
Explanation: C is the correct option.For a female to have haemophilia, she must inherit an affected X chromosome from each parent.
Correct answer: Mother is carrier, father is hemophiliac- A. Red-eyed males
- B. White-eyed males
- C. Red-eyed homozygous females
- D. White-eyed homozygous females
Explanation: Red eye homozygous female is not possible because female will inherit one white eye allele from father. So option C is correct.
Correct answer: Red-eyed homozygous females- A. Option A
- B. Option B
- C. Option C
- D. Option D
Explanation: A son must have the genotype XY, with X being inherited from mother and Y from father. Option B correctly represents it.
Correct answer: Option B- A. X chromosomes relative to the number of autosomes
- B. Y chromosomes relative to the number of autosomes
- C. Autosomes relative to the number of XY chromosomes
- D. Y chromosomes relative to the number of X chromosomes.
Explanation: In Drosophila, sex determination is based on the ratio of X chromosomes to sets of autosomes (A), rather than the presence of a Y…
Correct answer: X chromosomes relative to the number of autosomes- A. He inherited the recessive allele from his mother
- B. He inherited the dominant allele from his father
- C. He can pass the disease to a son
- D. He can pass a dominant allele to a daughter
Explanation: This statement is correct. Since hemophilia is an X-linked recessive disorder, a male with hemophilia inherits the affected X chromosome…
Correct answer: He inherited the recessive allele from his mother- A. Beard growth
- B. Baldness
- C. Haemophilia
- D. Tfm
Explanation: Testicular feminization, also known as androgen insensitivity syndrome (AIS), is a genetic condition in which individuals with XY…
Correct answer: TfmX-linked Recessive Inheritance MCQs: common questions
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