Page 138 - NCERT Science Class 10 English Medium

Q U E S T I O N S

1. How do Mendel’s experiments show that traits may be dominant or
recessive?
2. How do Mendel’s experiments show that traits are inherited
independently? ?
3. A man with blood group A marries a woman with blood group O and
their daughter has blood group O. Is this information enough to tell you
which of the traits – blood group A or O – is dominant? Why or why not?
4. How is the sex of the child determined in human beings?

What you have learnt

n Variations arising during the process of reproduction can be inherited.
n These variations may lead to increased survival of the individuals.
n Sexually reproducing individuals have two copies of genes for the same trait. If the
copies are not identical, the trait that gets expressed is called the dominant trait
and the other is called the recessive trait.
n Traits in one individual may be inherited separately, giving rise to new combinations
of traits in the offspring of sexual reproduction.
n Sex is determined by different factors in various species. In human beings, the
sex of the child depends on whether the paternal chromosome is X (for girls) or Y
(for boys).

E X E R C I S E S

1. A 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
2. A 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?
3. Outline a project which aims to find the dominant coat colour in dogs.
4. How is the equal genetic contribution of male and female parents ensured in
the progeny?

Heredity 133

2024-25