Part 8: Mixed & Advanced MCQs (Revision & NEET-level)
Part 8: Mixed & Advanced MCQs (Revision & NEET-level)
Q176. Which of the following cross disproves Mendel’s law of independent assortment?
a) Monohybrid cross
b) Dihybrid cross involving linked genes
c) Back cross
d) Reciprocal cross
Answer: b
- b) Correct: Linked genes do not assort independently.
- a, c, d) Do not violate the law.
Q177. The frequency of recombination between two genes is used to measure:
a) Strength of dominance
b) Genetic distance
c) Mutation rate
d) Number of alleles
Answer: b
- b) Correct: Recombination frequency (in %) = genetic distance in centimorgans.
Q178. A test cross with F1 dihybrid (AaBb × aabb) gives progeny ratio 1:1:1:1. This indicates:
a) Independent assortment
b) Complete linkage
c) Incomplete dominance
d) Mutation
Answer: a
- a) Correct: 1:1:1:1 test cross ratio = independent assortment.
Q179. A red snapdragon crossed with a white snapdragon gives pink offspring. The F2 ratio will be:
a) 3:1
b) 1:2:1
c) 9:3:3:1
d) 2:1
Answer: b
- b) Correct: Incomplete dominance = 1 red : 2 pink : 1 white.
Q180. A child with blood group O is born to parents with groups A and B. Which is the possible genotype of parents?
a) IAIA × IBIB
b) IAi × IBi
c) IAIA × IBi
d) IAi × IBIB
Answer: b
- b) Correct: Only IAi × IBi can give child with ii (O).
Q181. Which of the following disorders is both pleiotropic and codominant?
a) Thalassemia
b) Sickle-cell anemia
c) Hemophilia
d) Color blindness
Answer: b
- b) Correct: Sickle-cell anemia shows pleiotropy and codominance.
Q182. Which of the following inheritance patterns produces continuous variation?
a) Monohybrid inheritance
b) Polygenic inheritance
c) Codominance
d) Incomplete dominance
Answer: b
- b) Correct: Polygenic inheritance (e.g., human height, skin color).
Q183. A woman with genotype IAIB marries a man with genotype IBi. What fraction of their children may have blood group O?
a) 0
b) 1/4
c) 1/2
d) 1
Answer: a
- a) Correct: Cross does not produce ii genotype → no O blood group.
Q184. The chromosomal basis of sex determination in humans is best explained by:
a) Morgan
b) Sutton-Boveri theory
c) Lyon’s hypothesis
d) Mendel
Answer: b
- b) Correct: Sutton–Boveri → chromosomes are basis of inheritance, including sex chromosomes.
Q185. Which mechanism determines sex in honey bees?
a) XY type
b) ZW type
c) XO type
d) Haplodiploidy
Answer: d
- d) Correct: Honey bees follow haplodiploid system.
Q186. Which is the correct genetic makeup of a Down’s syndrome female?
a) 44 autosomes + XX
b) 44 autosomes + XY + extra 21
c) 44 autosomes + XX + extra 21
d) 43 autosomes + XX
Answer: c
- c) Correct: Down’s female = 47 chromosomes (extra chromosome 21).
Q187. In Morgan’s Drosophila experiments, recombination frequency between two linked genes was always:
a) Greater than 50%
b) Less than 50%
c) Equal to 100%
d) Zero
Answer: b
- b) Correct: Linked genes show < 50% recombination.
Q188. Which of the following traits in humans is Y-linked (holandric)?
a) Color blindness
b) Hemophilia
c) Hairy pinna
d) Sickle-cell anemia
Answer: c
- c) Correct: Hairy pinna/ear lobe = Y-linked trait.
Q189. Carrier females for color blindness have probability of passing the defective allele to their sons as:
a) 0%
b) 25%
c) 50%
d) 100%
Answer: c
- c) Correct: Carrier mother (XcX) → 50% sons will inherit Xc and be color-blind.
Q190. Which chromosomal disorder results from nondisjunction of sex chromosomes?
a) Down’s syndrome
b) Turner’s syndrome
c) Cri-du-chat syndrome
d) Edwards syndrome
Answer: b
- b) Correct: Turner’s (XO) → nondisjunction of sex chromosome.
Q191. Which of the following is a structural chromosomal disorder?
a) Turner’s syndrome
b) Down’s syndrome
c) Cri-du-chat syndrome
d) Klinefelter’s syndrome
Answer: c
- c) Correct: Cri-du-chat = deletion of chromosome 5 short arm.
Q192. Which condition results in sterile males with breast enlargement?
a) Turner’s syndrome
b) Klinefelter’s syndrome
c) Down’s syndrome
d) Edwards syndrome
Answer: b
- b) Correct: Klinefelter’s (XXY) → sterile tall males with gynecomastia.
Q193. A trisomic human female with mental retardation and flat face is likely suffering from:
a) Edwards syndrome
b) Patau syndrome
c) Down’s syndrome
d) Turner’s syndrome
Answer: c
- c) Correct: Classic features of Down’s syndrome.
Q194. If recombination frequency between two genes is 1%, the distance between them is:
a) 1 base pair
b) 1 centimorgan
c) 1 kilobase
d) 1 micron
Answer: b
- b) Correct: 1% recombination = 1 cM genetic distance.
Q195. Which stage of meiosis is crossing over initiated?
a) Leptotene
b) Zygotene
c) Pachytene
d) Diplotene
Answer: c
- c) Correct: Crossing over = pachytene stage.
Q196. Which of the following disorders is autosomal dominant?
a) Huntington’s chorea
b) Sickle-cell anemia
c) Thalassemia
d) Hemophilia
Answer: a
- a) Correct: Huntington’s = autosomal dominant.
Q197. Which disorder shows heterozygote advantage in malaria-endemic regions?
a) Thalassemia
b) Sickle-cell anemia
c) Hemophilia
d) Down’s syndrome
Answer: b
- b) Correct: Heterozygotes for sickle-cell (AS) resist malaria.
Q198. Polygenic inheritance differs from pleiotropy because:
a) One gene affects many traits in polygenic
b) Many genes affect one trait in pleiotropy
c) Both involve multiple genes
d) Polygenic = many genes for one trait; Pleiotropy = one gene for many traits
Answer: d
- d) Correct: Key distinction between polygenic & pleiotropy.
Q199. The law of segregation is also known as:
a) Law of purity of gametes
b) Law of dominance
c) Law of independent assortment
d) Law of linkage
Answer: a
- a) Correct: Segregation law = law of purity of gametes.
Q200. Which one of the following is INCORRECT?
a) Down’s syndrome – Trisomy 21
b) Turner’s syndrome – XO
c) Klinefelter’s syndrome – XXY
d) Edwards syndrome – Trisomy 13
Answer: d
- d) Correct: Edwards = trisomy 18, not 13. (Trisomy 13 = Patau syndrome).
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