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ISC Class 12 Genetics and Evolution — practice questions — page 4

Explore 109 free Genetics and Evolution questions in ISC Class 12 Biology. Open each question or exercise to read its content, reference answers and available explanation.

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Genetics and Evolution questions and exercises with answers

Showing questions 91–109 of 109.

The Hardy-Weinberg principle's equation for genotype frequencies is:Read the answer and worked solution →The total number of possible codons in the genetic code isRead the answer and worked solution →In a DNA double helix, adenine pairs with thymine throughRead the answer and worked solution →In DNA, Adenine (A) pairs with Thymine (T) via:Read the answer and worked solution →Match each disorder to its chromosomal / genetic cause.Read the answer and worked solution →NEET · Biology · Molecular Basis of Inheritance · Tap RNA-Only Bases / SugarsRead the answer and worked solution →The 14 species of finches that Darwin observed on the Galapagos Islands are a classic example of:Read the answer and worked solution →The two strands of a DNA double helix areRead the answer and worked solution →NEET · Bio · Principles of Inheritance · Blood Group ↔ GenotypeRead the answer and worked solution →DNA base pairing.Read the answer and worked solution →The genotypic ratio in the F₂ of a monohybrid cross between Tt × Tt isRead the answer and worked solution →NEET · Biology · ABO Blood Group — Genotype ↔ PhenotypeRead the answer and worked solution →The Lac Operon in E. coli is INDUCED (turned ON) by the presence of:Read the answer and worked solution →The Human Genome Project (HGP) ran from 1990 to:Read the answer and worked solution →The Miller-Urey experiment (1953) demonstrated that:Read the answer and worked solution →NEET · Bio · Principles of Inheritance · Mendel's LawsRead the answer and worked solution →Dominant or recessive?Read the answer and worked solution →Genotype and phenotypeRead the answer and worked solution →NEET · Biology · Spot the Error — Genetics PYQsRead the answer and worked solution →

Worked practice questions

The Hardy-Weinberg principle's equation for genotype frequencies is:

  1. $p + q = 1$ (allele frequency sum)
  2. $p^2 + 2pq + q^2 = 1$ (genotype freq.)
  3. $p^2 - q^2 = 1$ (difference)
  4. $p + 2pq + q = 1$ (mixed sum)
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Correct answer: B. $p^2 + 2pq + q^2 = 1$ (genotype freq.)

**Hardy-Weinberg:** if p = freq of allele A and q = freq of allele a then p² + 2pq + q² = 1 gives genotype freq (p² for AA, 2pq for Aa, q² for aa). p + q = 1 is the allele-freq constraint.

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The total number of possible codons in the genetic code is

  1. 16
  2. 64
  3. 20
  4. 256
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Correct answer: B. 64

A codon is a triplet of RNA bases each base has 4 possibilities, so the total is 4³ = 64 codons. These 64 codons map to 20 amino acids (degenerate code) plus three stop signals.

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In a DNA double helix, adenine pairs with thymine through

  1. one hydrogen bond
  2. two hydrogen bonds
  3. three hydrogen bonds
  4. a covalent bond
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Correct answer: B. two hydrogen bonds

A and T form two hydrogen bonds; G and C form three. The unequal counts explain why G-C-rich regions are more thermally stable than A-T-rich regions.

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