Class 10 Science: Heredity important questions

Heredity is a chapter of Class 10 Science for the Andhra Pradesh State Board. These 10 questions are marked Very Important, Important or Practice, and each answer has been checked by our team. Use them to revise, not as a prediction of what will come in the exam.

1. Practice · 1 marks

   1. The transfer of characters from parents to offspring is called ________.

   Heredity (inheritance).

2. Practice · 1 marks

   2. Species A shows a wide range of variation among its individuals; species B has individuals with very similar traits. If the environment changes suddenly, which is more likely to survive?

   Species A. With more variation, some individuals are likely to have traits that suit the new conditions, so they survive and reproduce. Variation helps a species survive changes.

3. Practice · 1 marks

   3. In a population of an asexually reproducing species, trait A is present in 10% of individuals and trait B in 60%. Which trait probably arose earlier?

   Trait B. In asexual reproduction, a trait that arose earlier has had more generations to be passed on, so it is found in more individuals.

4. Very Important · 8 marks

   4. How do Mendel's experiments show that traits are inherited independently?

   Mendel crossed pea plants differing in two characters: round, yellow seeds (RRYY) × wrinkled, green seeds (rryy). F1: all plants had round, yellow seeds (RrYy). Round and yellow are dominant. F2 (F1 self-pollinated): four types appeared in the ratio 9 : 3 : 3 : 1: round yellow 9, round green 3, wrinkled yellow 3, wrinkled green 1. New combinations (round green and wrinkled yellow) appeared that were not in either parent. So the gene for seed shape and the gene for seed colour were passed on independently of each other.

5. Practice · 1 marks

   5. In Mendel's monohybrid cross, the F2 phenotypic ratio is A) 3 : 1 B) 1 : 2 : 1 C) 9 : 3 : 3 : 1

   A) 3 : 1 (three dominant : one recessive). 1 : 2 : 1 is the genotypic ratio, and 9 : 3 : 3 : 1 is for a dihybrid cross.

6. Important · 2 marks

   6. What contrasting visible characters of the pea plant did Mendel study?

   Mendel studied seven pairs of contrasting characters: Tall / dwarf stem; round / wrinkled seeds; yellow / green seeds; violet / white flowers; axial / terminal flowers; green / yellow pods; inflated / constricted pods.

7. Very Important · 8 marks

   7. How is the sex of a child determined in human beings?

   Humans have 23 pairs of chromosomes; one pair are the sex chromosomes. Females have XX and males have XY. All egg cells from the mother carry an X chromosome. Half the father's sperm carry X and half carry Y. If a sperm with X fertilises the egg, the child is XX: a girl. If a sperm with Y fertilises the egg, the child is XY: a boy. So the sex of the child is decided by the sperm from the father, with an equal (50%) chance of a boy or a girl.

8. Practice · 1 marks

   8. A pea plant with round, yellow seeds (RRYY) is crossed with one with wrinkled, green seeds (rryy). The F1 plants are A) RRyy B) RRYY C) RrYy D) rrYY

   C) RrYy. Every F1 plant gets R and Y from one parent and r and y from the other, so all F1 plants have round, yellow seeds.

9. Practice · 1 marks

   9. Who proposed the rules of inheritance?

   Gregor Johann Mendel.

10. Very Important · 8 marks

    10. "Traits may be dominant or recessive." Explain this using Mendel's experiments.

    Mendel crossed a pure tall pea plant (TT) with a pure dwarf plant (tt). F1 generation: all plants were tall (Tt). The dwarf trait did not appear, so tall is the dominant trait. He then self-pollinated the F1 plants. F2 generation: tall and dwarf plants appeared in the ratio 3 : 1 (TT, Tt, Tt tall; tt dwarf). The dwarf trait reappeared in F2, so it had been present but hidden in F1: it is the recessive trait. Conclusion: a dominant trait shows even when only one copy is present; a recessive trait shows only when both copies are recessive.