Heredity

17 solved questions from Class 10 Science, each with the full working. Tap any question to see the step-by-step solution.

• 1 A colour‑blindness (X‑linked recessive) gene is represented by ‘c’. If a normal‑vision male (XY) marries a carrier female (XcX), what is the expected proportion of colour‑blind sons? hard MCQ 3 marks Sex‑linked inheritance
• 2 According to Mendel’s law of dominance, when a pure‑bred tall pea plant (TT) is crossed with a pure‑bred dwarf plant (tt), the F1 generation shows which phenotype? easy MCQ 1 mark Law of dominance
• 3 In humans, the allele for attached earlobes (a) is recessive to the allele for free earlobes (A). If two heterozygous individuals (Aa) marry, what is the probability that their child will have attached earlobes? medium 2 marks Mendelian probability
• 4 Albinism is an autosomal recessive disorder (aa = affected, AA or Aa = normal). The grandparents, both phenotypically normal, have two children: one affected (aa) and one normal. The normal daughter (who is phenotypically normal) marries an unrelated normal man, and they have three children, two of whom are affected and one is normal. Assuming no new mutations, determine the most likely genotypes of the grandparents, the normal daughter, and her husband. hard 5 marks Autosomal recessive pedigree analysis
• 5 When a pure‑bred tall pea plant (TT) is crossed with a pure‑bred dwarf plant (tt), what will be the phenotype of the entire F1 generation? easy MCQ 1 mark Mendel’s law of dominance
• 6 In a dihybrid cross RrYy × RrYy, what is the probability that an offspring will have round seeds (R) and yellow seed colour (Y)? medium 3 marks Independent assortment in dihybrid cross
• 7 Hemophilia is an X‑linked recessive disorder represented by allele h (recessive) and H (normal). A carrier mother (XHXh) marries a normal‑vision male (XHY). What percentage of their sons will be affected and what percentage of their daughters will be carriers? medium 4 marks Sex‑linked inheritance
• 8 A colour‑blind male (genotype XcY) marries a woman who is a carrier for colour‑blindness (genotype XCXc). What proportion of their daughters will be colour‑blind? medium MCQ 2 marks X‑linked recessive inheritance – daughters
• 9 In a certain family, a disorder is autosomal dominant (allele D) and appears in every generation. Two affected individuals, both known to be heterozygous (Dd), have four children. How many of the children are expected to be affected by the disorder? medium 3 marks Autosomal dominant inheritance – heterozygous cross
• 10 Genes A and B are located on the same chromosome and are 20 % recombination apart. A plant heterozygous for both genes in coupling phase (genotype AB/ab) is crossed with a plant homozygous recessive (ab/ab). What is the probability that an offspring will inherit the recombinant genotype Ab? hard 4 marks Linked genes and recombination frequency
• 11 In pea plants, the allele for round seed shape (R) is dominant over the allele for wrinkled seed shape (r). If a plant heterozygous for seed shape (Rr) is crossed with a plant homozygous recessive (rr), what percentage of the progeny will have round seeds? easy MCQ 1 mark Monohybrid cross – phenotype ratio
• 12 Define the term ‘carrier’ in genetics and illustrate it with a specific example of an autosomal recessive disorder. easy 2 marks Carrier concept in autosomal recessive inheritance
• 13 What is the primary topic or theoretical principle explored in 'Heredity' (Class 10 SCIENCE)? medium MCQ Chapter Core Principle
• 14 Which key mechanism or analytical rule is highlighted in 'Heredity'? medium MCQ Key Analytical Mechanism
• 15 A family has an X‑linked recessive disorder. The mother is a carrier (XcX) and the father is normal (XY). They have three children: one son who is color‑blind, and two daughters who are normal. What is the probability that their next child (fourth) will be a son with color‑blindness? hard 3 marks X‑linked recessive inheritance
• 16 If two carriers of an autosomal recessive disease (Aa) have four children, how many children are expected to be affected? medium 2 marks Autosomal recessive inheritance
• 17 A family has an autosomal recessive disease. Both parents are phenotypically normal. They have one affected child (aa) and one normal child. Assuming no mutation, what are the most likely genotypes of the parents and what is the probability that their next child will be affected? hard 4 marks Autosomal recessive inheritance