Heredity & Evolution

Exemplar Problems MCQ I

Exchange of genetic material takes place in

  1. vegetative reproduction
  2. asexual reproduction
  3. sexual reproduction
  4. budding

    Answer: (c) Sexual reproduction

Explanation: In case of sexual reproduction, two individuals contribute towards the genes of the offspring. Hence, sexual reproduction is the correct answer.

Two pink coloured flowers on crossing resulted in 1 red, 2 pink and 1 white flower progeny. The nature of the cross will be

  1. double fertilization
  2. self pollination
  3. cross fertilization
  4. no fertilization

    Answer: (c) Cross fertilization

Explanation: The term ‘cross’ in the question gives the clue for this answer.

A cross between a tall plant (TT) and short pea plant (tt) resulted in progeny that were all tall plants because

  1. tallness is the dominant trait
  2. shortness is the dominant trait
  3. tallness is the recessive trait
  4. height of pea plant is not governed by gene ‘T’ or ‘t’

    Answer: (a) tallness is the dominant trait

Explanation: This is a case of monohybrid cross; in which all the progenies in the F1 generation show dominant character. Hence, tallness is the dominant trait.

Which of the following statement is incorrect?

  1. For every hormone there is a gene.
  2. For every protein there is a gene.
  3. For production of every enzyme there is a gene.
  4. For every molecule of fat there is a gene

    Answer: (d) For every molecule of fat there is a gene

Explanation: Hormone and enzymes are proteins and formation of any particular protein is controlled by a particular gene. Hence, all other options are correct.

If a round, green seeded pea plant (RR yy) is crossed with wrinkled, yellow seeded pea plant, (rr YY) the seeds produced in F1 generation are

  1. round and yellow
  2. round and green
  3. wrinkled and green
  4. wrinkled and yellow

    Answer: (a) round and yellow

Explanation: Since roundness and yellow colour are shown by capital letters in the genotype so they are dominant traits. We know that only dominant traits are expressed in F1 generation.

In human males all the chromosomes are paired perfectly except one. This/these unpaired chromosome is/are

  1. large chromosome
  2. small chromosome
  3. Y-chromosome
  4. X-chromosome
  1. (i) and (ii)
  2. (iii) only
  3. (iii) and (iv)
  4. (ii) and (iv)

    Answer: (d) (ii) and (iv)

Explanation: Y-chromosome is smaller and is the only unpaired chromosome in human males.

The maleness of a child is determined by

  1. the X chromosome in the zygote
  2. the Y chromosome in zygote
  3. the cytoplasm of germ cell which determines the sex
  4. sex is determined by chance

    Answer: (b) Y chromosome in zygote

Explanation: Y-chromosome in zygote means that the zygote would develop into a male child.

A zygote which has an X-chromosome inherited from the father will develop into a

  1. Boy
  2. Girl
  3. X- chromosome does not determine the sex of a child
  4. either boy or girl

    Answer: (b) Girl

Explanation: A zygote with XX chromosomes in the 23rd pair would develop into a girl child.

Select the incorrect statement

  1. Frequency of certain genes in a population change over several generations resulting in evolution
  2. Reduction in weight of the organism due to starvation is genetically controlled
  3. Low weight parents can have heavy weight progeny
  4. Traits which are not inherited over generations do not cause evolution

    Answer: (b) Reduction in weight of the organism due to starvation is genetically controlled

Explanation: Weight loss or gain happen because of external factors; especially availability of food. Genotype has no role to play in it. Hence, option ‘b’ shows incorrect statement.

New species may be formed if

  1. DNA undergoes significant changes in germ cells
  2. chromosome number changes in the gamete
  3. there is no change in the genetic material
  4. mating does not take place
  1. (i) and (ii)
  2. (i) and (iii)
  3. (ii), (iii) and (iv)
  4. (i), (ii) and (iii)

    Answer: (a) (i) and (ii)

Explanation: No change in the genetic material, and lack of mating cannot result in origin of new species.

Two pea plants one with round green seeds (RRyy) and another with wrinkled yellow (rrYY) seeds produce F1 progeny that have round, yellow (RrYy) seeds. When F1 plants are selfed, the F2 progeny will have new combination of characters. Choose the new combination from the following

  1. Round, yellow
  2. Round, green
  3. Wrinkled, yellow
  4. Wrinkled, green
  1. (i) and (ii)
  2. (i) and (iv)
  3. (ii) and (iii)
  4. (i) and (iii)

    Answer:
    (c) (ii) and (iii)

Explanation: This can be shown by following Punette square:

punette square

A basket of vegetables contains carrot, potato, radish and tomato. Which of them represent the correct homologous structures?

  1. Carrot and potato
  2. Carrot and tomato
  3. Radish and carrot
  4. Radish and potato

    Answer: (c) Radish and carrot

Explanation: Radish and carrot are modified tap roots. Organs/parts with similar design/origin are called homologous organs.

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