NEET (UG)

Practice Test 1 — Principles of Inheritance and Variation

12 questions • 18 minutes • auto-graded with full solutions

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Section A — MCQ (Single Correct)

Question 1

The number of contrasting traits Mendel studied in pea was:

Solution: Mendel studied seven pairs of contrasting traits.

Question 2

A cross of Tt × tt gives a phenotypic ratio of:

Solution: A test cross of a heterozygote gives 1:1.

Question 3

The 9:3:3:1 ratio supports the Law of:

Solution: Dihybrid 9:3:3:1 demonstrates Independent Assortment.

Question 4

In incomplete dominance, the F2 phenotypic ratio is:

Solution: It equals the genotypic ratio, 1:2:1.

Question 5

Blood group AB shows:

Solution: Both A and B antigens express — codominance.

Question 6

Linkage reduces the proportion of:

Solution: Linked genes give fewer recombinant types.

Question 7

Colour blindness is:

Solution: Red-green colour blindness is X-linked recessive.

Question 8

Turner's syndrome individuals are:

Solution: Turner's = 45, X0 (female).

Section B — Assertion & Reason

Question 9

A: In a monohybrid cross the recessive trait reappears in the F2 generation.
R: The recessive allele is present but masked in the F1 and segregates out during gamete formation.

Solution: Segregation of the masked recessive allele is why it reappears — R explains A.

Question 10

A: Colour blindness and haemophilia are more common in males than in females.
R: They are X-linked recessive, so a single defective X allele expresses the trait in males.

Solution: Males (XY) need only one defective X — R explains A.

Question 11

A: In incomplete dominance one allele completely masks the other.
R: The heterozygote of a cross showing incomplete dominance has an intermediate phenotype.

Solution: A is false — in incomplete dominance neither allele masks the other; R is true (the heterozygote is intermediate).

Question 12

A: Down's syndrome is a chromosomal disorder.
R: It results from an extra copy of chromosome 21 (trisomy 21).

Solution: An extra chromosome 21 makes it a chromosomal disorder — R explains A.