Part 5: Sex-linked Inheritance (25 MCQs)
Part 5: Sex-linked Inheritance (25 MCQs)
Q103. Sex-linked inheritance refers to genes located on:
a) Autosomes
b) Sex chromosomes
c) Mitochondria
d) Ribosomes
Answer: b
- b) Correct: Sex-linked inheritance = traits carried on sex chromosomes (X or Y).
- a) Autosomes → autosomal inheritance.
- c, d) Not relevant.
Q104. Which scientist first discovered sex-linked inheritance in Drosophila?
a) Mendel
b) Sutton
c) Morgan
d) Bateson
Answer: c
- c) Correct: T.H. Morgan → white-eyed mutation in Drosophila proved sex-linkage.
Q105. Hemophilia is caused by mutation in a gene located on:
a) Autosomes
b) X chromosome
c) Y chromosome
d) Mitochondrial DNA
Answer: b
- b) Correct: Hemophilia = X-linked recessive disorder.
Q106. A female carrier for hemophilia will have genotype:
a) XHXH
b) XhXh
c) XHXh
d) XHY
Answer: c
- c) Correct: Carrier female = heterozygous (XHXh).
- a) Normal female.
- b) Affected female.
- d) Male.
Q107. In humans, which sex is more frequently affected by X-linked recessive disorders?
a) Female
b) Male
c) Both equally
d) None
Answer: b
- b) Correct: Males have only one X chromosome (hemizygous) → recessive allele expresses.
Q108. Color blindness in humans is due to defect in:
a) Autosomal gene
b) Y chromosome
c) X chromosome
d) Mitochondria
Answer: c
- c) Correct: Color blindness = X-linked recessive trait.
Q109. A color-blind woman marries a normal man. What % of sons will be color-blind?
a) 0%
b) 25%
c) 50%
d) 100%
Answer: d
- d) Correct: Mother (XcXc) × Father (XY) → all sons (XcY) = 100% color-blind.
Q110. A carrier woman for color blindness marries a normal man. What % of sons will be color-blind?
a) 0%
b) 25%
c) 50%
d) 100%
Answer: c
- c) Correct: Cross (XcX × XY) → 50% sons color-blind (XcY).
Q111. Which type of inheritance does NOT skip generations?
a) Autosomal recessive
b) Autosomal dominant
c) X-linked recessive
d) Mitochondrial
Answer: b
- b) Correct: Autosomal dominant traits usually appear in every generation.
Q112. Which of the following is NOT an X-linked disorder?
a) Hemophilia
b) Color blindness
c) Duchenne muscular dystrophy
d) Sickle-cell anemia
Answer: d
- d) Correct: Sickle-cell anemia = autosomal, not X-linked.
Q113. Females are rarely affected by X-linked recessive disorders because:
a) They have two X chromosomes
b) They are stronger genetically
c) They have Y chromosomes
d) Mutation never occurs in females
Answer: a
- a) Correct: Two Xs → recessive allele masked by dominant allele.
Q114. If a hemophilic man marries a normal woman, their sons will be:
a) All hemophilic
b) All normal
c) 50% hemophilic
d) 25% hemophilic
Answer: b
- b) Correct: Father gives Y to sons → they inherit mother’s normal X → all normal.
Q115. In the same cross (hemophilic man × normal woman), their daughters will be:
a) All normal
b) All carriers
c) All hemophilic
d) 50% hemophilic
Answer: b
- b) Correct: Daughters get Xh from father + X from mother → all carriers.
Q116. A woman can be hemophilic only if:
a) Father is hemophilic
b) Mother is hemophilic
c) Both parents contribute defective X
d) Either parent is hemophilic
Answer: c
- c) Correct: Woman must inherit defective X from both parents (rare).
Q117. Which gene is present on Y chromosome in humans?
a) Hemophilia gene
b) Color blindness gene
c) SRY gene
d) ABO blood group gene
Answer: c
- c) Correct: SRY (sex-determining region Y) → initiates testis development.
Q118. Y-linked inheritance is also called:
a) Holandric inheritance
b) Autosomal inheritance
c) Cytoplasmic inheritance
d) Maternal inheritance
Answer: a
- a) Correct: Traits inherited through Y chromosome → holandric inheritance.
Q119. Which of the following is an example of Y-linked trait in humans?
a) Hemophilia
b) Hypertrichosis (hairy ears)
c) Color blindness
d) Thalassemia
Answer: b
- b) Correct: Hairy pinna/ears = Y-linked trait.
Q120. Pedigree analysis is used to study:
a) Sex-linked traits
b) Autosomal traits
c) Mode of inheritance of traits
d) All of the above
Answer: d
- d) Correct: Pedigree analysis = study of inheritance patterns (autosomal and sex-linked).
Q121. In pedigree charts, females are represented by:
a) Square
b) Circle
c) Triangle
d) Diamond
Answer: b
- b) Correct: Females = circle, Males = square.
Q122. Which symbol represents carriers in pedigree charts?
a) Half-shaded circle/square
b) Fully shaded circle/square
c) Open circle/square
d) Diamond
Answer: a
- a) Correct: Carriers = half-shaded symbol.
Q123. If a trait passes from father to all sons but never to daughters, it is:
a) Autosomal recessive
b) X-linked recessive
c) Y-linked (holandric)
d) Mitochondrial
Answer: c
- c) Correct: Y-linked traits → passed from father to all sons only.
Q124. Why are sex-linked disorders useful in genetics studies?
a) They are common in population
b) They help trace inheritance patterns easily
c) They only affect males
d) They never skip generations
Answer: b
- b) Correct: Their inheritance is clear and traceable in pedigrees.
Q125. In color blindness, which colors are mainly affected?
a) Red and green
b) Blue and yellow
c) Black and white
d) Pink and orange
Answer: a
- a) Correct: Red-green color blindness is most common.
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