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1.5 Mendel's Laws, Dihybrid & Gene Interactions — Test 2
Q1. The chromosomal theory of heredity (genes are located on chromosomes) was first proposed by:✓ Walter Sutton (and Theodor Boveri)
Q2. Mendel's principle that genes for different traits are passed independently is the law of:✓ Independent assortment
Q3. Mendel chose the garden pea (Pisum sativum) partly because it is normally:✓ Self-fertilising (with easily controlled crosses)
Q4. The phenotypic ratio of the F2 generation in a standard dihybrid cross is:✓ 9:3:3:1
Q5. Which process during meiosis provides the physical basis for Mendel's laws?✓ Separation (segregation) of homologous chromosomes
Q6. In the cross TtYy × ttyy, the probability of obtaining a TT offspring is:✓ 0%
Q7. A cross between a true-breeding red-flowered and a true-breeding white-flowered plant gives all pink F1. This illustrates:✓ Incomplete dominance
Q8. In the human ABO system, a child with blood group O has a father with blood group B. The father's genotype must be:✓ IᴮIᴼ
Q9. A cross CCPP × ccpp gives coloured F1; the F2 shows a 9 coloured : 7 colourless ratio. This indicates:✓ Complementary gene interaction
Q10. The modified F2 phenotypic ratio characteristic of dominant epistasis is:✓ 12:3:1
Q11. An organism that is heterozygous (Tt) for a trait, where T (tall) is dominant, will be phenotypically:✓ Tall
Q12. In a pedigree chart, a male who is a heterozygous carrier of an autosomal recessive trait is conventionally shown as a:✓ Half-shaded (or dotted) square
Q13. Mendel's law of segregation states that:✓ Two alleles of a gene separate during gamete formation
Q14. When a heterozygote expresses both alleles fully and simultaneously (e.g. AB blood group), this is:✓ Codominance
Q15. A trait determined by one gene that affects several different characteristics is an example of:✓ Pleiotropy
Q16. A test cross is performed by crossing an individual of unknown genotype with one that is:✓ Homozygous recessive
Q17. Recessive epistasis produces which modified dihybrid F2 ratio?✓ 9:3:4
Q18. The reappearance of a recessive trait in the F2 generation (after an all-dominant F1) demonstrates:✓ Segregation of alleles
Q19. True-breeding (pure-line) organisms are:✓ Homozygous for the trait in question
Q20. Match each interaction with its F2 ratio and select the correct option.✓ A-iii, B-i, C-ii, D-iv