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JAMB Biology questions: Heredity and variation

36 questions with answers and explanations. Tap an option to check yourself.

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All topicsCell structure and organisation · 30Cellular activities · 32Co-ordination and control · 31Ecology · 38Evolution · 27Excretion · 30Growth · 27Heredity and variation · 36Nutrition · 34Reproduction · 33Respiration · 30Support and movement · 28Transport · 30Variety of organisms · 32

  1. Question 21· Heredity and variation· JAMB

    A homozygous tall pea plant (TT) is crossed with a homozygous short one (tt). The F1 plants are

    Explanation and discussion

  2. Question 22· Heredity and variation· JAMB

    Two parents of genotype AS have a child. What is the probability that the child is SS?

    Explanation and discussion

  3. Question 23· Heredity and variation· JAMB

    Two parents both have the genotype AS. What is the probability that their child will have the genotype SS?

    Explanation and discussion

  4. Question 24· Heredity and variation· JAMB

    A person who carries the sickle-cell gene but does not suffer from the disease has the genotype

    Explanation and discussion

  5. Question 25· Heredity and variation· JAMB

    Haemophilia is more common in men than in women because it is

    Explanation and discussion

  6. Question 26· Heredity and variation· JAMB

    Diagram for this question

    In the cross shown, T (tall) is dominant over t (dwarf). What percentage of the offspring are dwarf?

    Explanation and discussion

  7. Question 27· Heredity and variation· JAMB

    If a heterozygous tall plant (Tt) is crossed with a dwarf plant (tt), the ratio of tall to dwarf offspring is:

    Explanation and discussion

  8. Question 28· Heredity and variation· JAMB

    A scar on the skin is an example of

    Explanation and discussion

  9. Question 29· Heredity and variation· JAMB

    Down's syndrome is caused by

    Explanation and discussion

  10. Question 30· Heredity and variation· JAMB

    In a dihybrid cross between two double heterozygotes (AaBb × AaBb), the expected phenotypic ratio is

    Explanation and discussion

  11. Question 31· Heredity and variation· JAMB

    A mother is a carrier of haemophilia and the father is normal. What is the probability that a son of theirs has haemophilia?

    Explanation and discussion

  12. Question 32· Heredity and variation· JAMB

    A test cross is used to find out whether an organism showing a dominant trait is

    Explanation and discussion

  13. Question 33· Heredity and variation· JAMB

    Genes are located on

    Explanation and discussion

  14. Question 34· Heredity and variation· JAMB

    Which of the following is an example of continuous variation?

    Explanation and discussion

  15. Question 35· Heredity and variation· JAMB

    In peas, round seed (R) is dominant to wrinkled seed (r). What fraction of the offspring of Rr × rr will be wrinkled?

    Explanation and discussion

  16. Question 36· Heredity and variation· JAMB

    An organism with two identical alleles for a trait is

    Explanation and discussion

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