MPBSE Class 10 Science Chapter 9 Heredity Question And Answers

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MPBSE Class 10 Science Chapter 9 Heredity Question And Answers

Question 1. In a monohybrid cross between tall Pea plants TT and short Pea plants tt, a scientist obtained only tall Pea plants Tt in the F1 generation. However, on selling the F1 generation Pea plants he obtained both tall and short plants in the F2 generation. Based on the above observations and with other angiosperms also, can the scientist arrive at a law? If yes, explain the law. If not, give a justification for your answer.
Answer:

There are two possibilities for the occurrence of tall plants in the F1 generation :

  • Only the factor for tallness passed into F1 progeny. Both the alleles of tallness and shortness passed into F1 progeny but only the allele of tallness is expressing itself.
  • The second option is correct because the trait of shortness has appeared in the F2 generation.
  • Again this can happen only when the alleles for the two traits separate during gamete formation and randomly come together during fertilization.
  • The scientist could, therefore, deduce the laws out of these observations : (1) Law of dominance. (2) Law of segregation.

Question 2.

  1. List two differences in tabular form between dominant and recessive traits.
  2. What percentage or proportion of the plants in F2 generation or progeny was round in Mendel’s cross between round and wrinkled seeded Pea plants?

Differences Between Dominant And Recessive Traits

Answer: (1)

Heredity Difference between Dominant trait And recessive Trait

2. 75% of plants had round seeds while 25% of plants had wrinkled seeds. The ratio is 3: 1.

Mpbse Class 10 Science Chapter 9 Solutions

Question 3. “A trait may be inherited but may not be expressed.” Justify the statement with the help of a suitable example.
Answer:

  1. The trachea is a cylindrical conduit for air from the pharynx to the lungs.
  2. The lining epithelium captures dust particles and bacteria, expelling them forth.
  3. The trachea remains patent despite lower air pressure owing to the presence of C-shaped cartilaginous rings.

Question 4. Name the plant Mendel used for his experiment. What type of progeny was obtained by Mendel in F1 and F1 generations when he crossed tall and short plants? Write the ratios he obtained in F2 generation plants.
Answer:

Garden Pea (Pisum sativum)

F1 Generation. All tall.

F2 Generation. 3 tall: 1 short or 3: 1

or 1 pure tall: 2 hybrid tall: 1 dwarf or 1: 2: 1.

Question 5.

  1. Why did Mendel experiment to study the inheritance of two traits in garden peas?
  2. What were his findings concerning the inheritance of traits in the F1 and F2 generations?
  3. State the ratio obtained in the F2 generation in the above-mentioned experiment.

Answer:

  1. To study the independent inheritance of traits/factors of different characters.
  2. F1 Progeny. All dominant. F2 Progeny. Both parental traits as well as some new combinations or recombinants.
  3. 9 : 3 : 3: 1 where 9/16 and 1/16 are parental types while two types of recombinants appear in the ratio of 3/16 and 3/16.

Heredity Class 10 Questions And Answers

Question 6. A green-stemmed rose plant denoted by GG and a brown-stemmed rose plant denoted by GG are allowed to undergo a cross with each other.

1. List your observations regarding (z) the Colour of the stem in the F1 progeny and the Percentage of brown stemmed plants in F2 progeny if F1 plants are self-pollinated. The ratio of GG and Gg in F2 progeny.

2. Based on the findings of this cross, what conclusion can be drawn?

Answer:

  1. Colour in F1 Progeny. Green
  2. Percentage of Brown Stemmed Plants in F2 Progeny. 25%
  3. Ratio of GG and Gg in F2 Progeny. 1: 2.

Conclusion: The trait which is expressed in whole F1 progeny is dominant while the other trait which remains unexpressed in F1 progeny but reappears in F2 progeny is recessive.

Question 7.

  1. Why is the F1 progeny always of tall plants when a tall pea plant is crossed with a short pea plant?
  2. How is F2 progeny obtained by self-pollination of F1 progeny different from F1 progeny? Give a reason for this observation.
  3. State a conclusion that can be drawn based on this observation.

Answer:

  1. The trait or factor for tallness is dominant while the trait for shortness is recessive.
  2. The recessive trait appears in the F2 generation due to its segregation during gamete formation and the random coming together of the two traits or factors during fertilization. When two factors of shortness come together the recessive trait will appear.
  3. The traits or factors are particulate structures which do not get destroyed or blend during inheritance.

Question 8. Mendel crossed two plants with visible contrasting characteristics and found that there were no halfway characteristics in the plants of F1 progeny. Explain the reason for this observation of Mendel.
Answer:

Despite having inherited both the contrasting traits, F1 progeny shows the trait of only one parent. This is because in the hybrid (F1 plants) only one trait expresses its effect. The trait is dominant. The other trait which does not express its effect in the hybrid is called recessive.

Law Of Inheritance Class 10 Biology

Question 9. What are chromosomes? Explain stability of the DNA of the species is ensured in sexually reproducing organisms.
Answer:

  • Chromosomes are thread-like entities based in the nucleus. Their DNA contains the genetic elements of the species. Every cell contains two copies of each chromosome.
  • In germ cells, generated post-meiosis, just one chromosome of each kind is present.
  • It may be either paternal or maternal. During fertilization, two gametes merge, reinstating the diploid state of chromosomes in the zygote and the subsequent cells of the organism derived from it.

Question 10.

  1. Name the two types of gametes produced by men.
  2. Does a male child inherit an X chromosome from his father? Justify.
  3. How many types of gametes are produced by a human female?

Answer:

  1. Men produce two types of sperms, X-carrying (gymnosperms) and Y-carrying (angiosperms) in equal proportion.
  2. No. A male child inherits the X chromosome from his mother. From their father, he inherits the Y chromosome.
  3. The female produces only one type of ova. They carry X chromosomes.

 

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