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NCERT Exemplar · Class 10 Science Heredity and Evolution

47 questions · 47 still being checked

Multiple Choice Questions 1–10 (part 1 of 5)

  1. Exercise 1

    Exchange of genetic material takes place in
    (a)
    vegetative reproduction
    (b)
    asexual reproduction
    (c)
    sexual reproduction
    (d)
    budding

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    NCERT’s answer
    (c)
    (c) Sexual reproduction. Gametes from two parents fuse at fertilisation, so the zygote's genetic material comes from both parents -- an exchange absent in vegetative or asexual modes such as budding.Answer: Sexual reproduction.

  2. Exercise 2

    Two pink coloured flowers on crossing resulted in 1\displaystyle 1 red, 2\displaystyle 2 pink and 1\displaystyle 1 white flower progeny. The nature of the cross will be
    (a)
    double fertilisation
    (b)
    self pollination
    (c)
    cross fertilisation
    (d)
    no fertilisation

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    NCERT’s answer
    (b)
    (b) Self pollination. Pink is the heterozygote \(\displaystyle Rr\) under incomplete dominance; two pink parents are genetically alike, so the cross behaves as a self. \[Rr \times Rr \rightarrow 1\,RR\,(\text{red}) : 2\,Rr\,(\text{pink}) : 1\,rr\,(\text{white}) \]

  3. Exercise 3

    A cross between a tall plant (TT) and short pea plant (tt) resulted in progeny that were all tall plants because
    (a)
    tallness is the dominant trait
    (b)
    shortness is the dominant trait
    (c)
    tallness is the recessive trait
    (d)
    height of pea plant is not governed by gene 'T' or 't'

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    (a)
    (a) Tallness is the dominant trait. \[TT \times tt \rightarrow F_1:\ Tt \] Every \(\displaystyle F_1\) plant is heterozygous \(\displaystyle Tt\); since all are tall, the tall allele masks the short one in the heterozygote.Answer: Tallness is the dominant trait.

  4. Exercise 4

    Which of the following statement is incorrect?
    (a)
    For every hormone there is a gene.
    (b)
    For every protein there is a gene.
    (c)
    For production of every enzyme there is a gene.
    (d)
    For every molecule of fat there is a gene

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    (d)
    (d) Genes code for proteins -- enzymes and protein hormones. Fat is not a protein; a gene codes the enzyme that builds it, not the fat. \[\text{gene} \rightarrow \text{enzyme (protein)} \rightarrow \text{fat} \]

  5. Exercise 5

    If a round, green seeded pea plant (RR yy) is crossed with wrinkled, yellow seeded pea plant, (rr YY) the seeds produced in F1\displaystyle \mathrm{F}_1 generation are
    (a)
    round and yellow
    (b)
    round and green
    (c)
    wrinkled and green
    (d)
    wrinkled and yellow

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    (a)
    (a) Round and yellow. \[RR\,yy \times rr\,YY \rightarrow F_1:\ Rr\,Yy \] Both loci are heterozygous; round (\(\displaystyle R\)) and yellow (\(\displaystyle Y\)) are the dominant alleles, so every \(\displaystyle F_1\) seed shows both dominant traits.Answer: Round and yellow.

  6. Exercise 6

    In human males all the chromosomes are paired perfectly except one. This/these unpaired chromosome is/are
    (i)
    large chromosome
    (ii)
    small chromosome
    (iii)
    Y-chromosome
    (iv)
    X-chromosome
    (a) (i) and (ii)
    (b) (iii) only
    (c) (iii) and (iv)
    (d) (ii) and (iv)

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    (c)
    (c) (iii) and (iv). Autosomes form $\displaystyle 22$ matched pairs; \(\displaystyle X\) and \(\displaystyle Y\) differ in size and genes, so neither has a true partner. \[22 \times 2 + X + Y = 46\ \text{chromosomes} \]

  7. Exercise 7

    The maleness of a child is determined by
    (a)
    the X chromosome in the zygote
    (b)
    the Y chromosome in zygote
    (c)
    the cytoplasm of germ cell which determines the sex
    (d)
    sex is determined by chance

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    NCERT’s answer
    (b)
    (b) The Y chromosome in the zygote. \[XX_{(\text{mother})} \times XY_{(\text{father})} \rightarrow \tfrac{1}{2}\,XX,\ \tfrac{1}{2}\,XY \] The father's sperm carries \(\displaystyle X\) or \(\displaystyle Y\); fertilisation by a \(\displaystyle Y\)-bearing sperm gives an \(\displaystyle XY\) zygote, which develops as male.Answer: The Y chromosome in the zygote.

  8. Exercise 8

    A zygote which has an X-chromosome inherited from the father will develop into a
    (a)
    boy
    (b)
    girl
    (c)
    X- chromosome does not determine the sex of a child
    (d)
    either boy or girl

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    NCERT’s answer
    (b)
    (b) girl A zygote always receives an \(\displaystyle \mathrm{X}\) from the mother, so the child's sex is fixed by the father's gamete. The father here contributes \(\displaystyle \mathrm{X}\), giving \(\displaystyle \mathrm{XX}\) \(\displaystyle \rightarrow\) girl.

  9. Exercise 9

    Select the incorrect statement
    (a)
    Frequency of certain genes in a population change over several generations resulting in evolution
    (b)
    Reduction in weight of the organism due to starvation is genetically controlled
    (c)
    Low weight parents can have heavy weight progeny
    (d)
    Traits which are not inherited over generations do not cause evolution

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    (b)
    (b) weight loss from starvation is genetic This is the incorrect claim: starvation-induced weight loss is an acquired, non-heritable change in the body, not the germ-cell DNA, so it cannot itself drive evolution.

  10. Exercise 10

    New species may be formed if
    (i)
    DNA undergoes significant changes in germ cells
    (ii)
    chromosome number changes in the gamete
    (iii)
    there is no change in the genetic material
    (iv)
    mating does not take place
    (a) (i) and (ii)
    (b) (i) and (iii)
    (c) (ii), (iii) and (iv)
    (d) (i), (ii) and (iii)

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    (a)
    (a) (i) and (ii) Only heritable \(\displaystyle \mathrm{DNA}\)/chromosome-number changes arising in germ cells pass to offspring and can fix in a population; unchanged genetic material, (iii), gives no new species.