RBSE Solutions for Class10 Science Chapter 8 Heredity

The chapter Heredity explains the experiments conducted by John Mendel. He performed experiments of hybridisation on garden pea. These solutions have been prepared by experienced teachers.

If you are preparing for RBSE class 10 board exams, then these solutions of intext and end exercise questions will help you a lot.

These solutions cover a complete syllabus and will let you solve homework and assignments in an easy way.

 

Board	RBSE
Subject	Science
Chapter	Heredity
No. of Intext questions	6
No. of End exercise questions	4
Prescribed Book	NCERT Science

 

Heredity

 

Answers of Questions on Page 129

Q.1If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier?

Answer      

Trait B that exists in 60% of the population of an asexually reproducing species is likely to have arisen earlier.

 

Q.2How does the creation of variations in a species ensure evolution?

Answer     

The variations provide stability to the population of various species by preventing them from getting   extinct during adverse conditions. if Creation of variation favourable then it make the organism  better fit  to an environment  and it will ensure the evolution of species.

 

  Answers of Questions on Page 133

Q.1How do Mendel’s experiments show that traits may be dominate or recessive?

Answer      

Mendel performed experiments with pea plants (Pisum sativum) with contrasting characteristics tall and dwarf. Mendel performed cross   pollination and he got all tall plants in first generation (F₁).  So the characteristics appeared in first generation were called dominant and the characteristics that did not appear were called recessive

 

Q.2How does Mendel’s experiment show that traits are inherited independently?

Answer    

Mendel performed cross between pure tall and pure dwarf pea plants. In F₁ generation, all the plants produced were tall, when plants of F₁ generation allowed to self-pollinated (self-fertilized) again, then tall and dwarf plants were obtained in ratio of 3:1. So this shows that trait of tallness (T) and dwarfness (t)   were inherited independently.

 

Q.3A man with blood group A marries a woman with blood group O ad their daughter has blood group O. Is this information enough to tell you which of the traits-blood group A or O, is dominate? Why or why not?

Answer      

No, this information is not enough because each individual organism carries two alleles for one trait. The recessive trait occurs when two alleles are similar. Blood groups in human beings determined by the presence of a special protein. For blood group A, antigen A is formed that is represented by I^A. Perhaps father may have heterozygous combination having only on I^A gene. So this information is incomplete to tell which of the traits blood group A or B is dominant.   

 

Q.4How is the sex of the child determined in human beings?

Answer    

Sex determination in human beings is determined by sex chromosomes. Sex chromosomes in man ‘XY’ and in female ‘XX’. So male is heteromorphic and female is homomorphic. Ovum and sperms are produced by the process meosis. Ovum in female has ‘X’ chromosomes and sperms in male have chromosomes ‘X’ or ‘Y’.

            When ovum fuses with sperm having ‘X’ chromosome then zygote will develop into female child (XX) but when sperm having ‘Y’ chromosome fertilize with ovum(X), then zygote  will develop into male child (XY).

                                 

	X	X
X	XX girl	XX Girl
Y	XY boy	XY boy

 

Answers of End Exercise Questions

 

Q.1A Mendelian experiment consisted of breeding tall pea plants bearing violet flowers with short pea plants bearing white flowers. The progeny all bore violet flowers, but almost half of them were short. This suggests that the genetic make-up of the tall parent can be depicted as:

(a)TTWW               

(b)TTww

(c)TtWW                       

(d)TtWw

 

Answer        (b)  TtWW

 

 

Q.2A study found that children with light-coloured eyes are likely to have parents with light-coloured eyes. On this basis, can we say anything about whether the light eye colour trait is dominant or recessive? Why or why not?

 

Answer   

Yes, the children with light coloured eyes are likely to have parents with light-coloured eyes. We can say that light eye colour trait is dominant because traits are transmitted from parents to children and a dominant trait appears in F₁ generation.

 

Q.3 Outline a project which aims to find the dominant coat colour in dogs.

Answer     

Let coat colour B (Black) is dominant over coat colour b (white). Suppose a black homozygous male is mated with a white homozygous female, if in next generation all dogs are black then the dominant colour is black.

Parent	B	B
b	Bb	Bb
b	Bb	Bb

         

 Progeny with black coat

 

Q.4 How is the equal genetic contribution of male and female parents ensured in the progeny?

Answer      

A male gamete fuses with a female gamete in sexual reproduction Each gamete (sperm and ovum) has a single set genes or chromosomes. So, a diploid zygote has one set of genes from father and mother. In this way, male and female parents ensure equal genetic contribution in the progeny.