NCERT Solutions for Class 10 Science Ch 8: Heredity, is given below.
You will get solutions for;
- In-text questions as well as,
- Exercises questions.
So let’s dive into it!
In-text Questions Set-1
1) If a trait A exists in 10% of a population of an asexually reproducing species and trait B exists in 60% of the same population, which trait is likely to have arisen earlier?
Solution:
Trait B is more likely to appear early because it already exists and is more common in the population than Trait A.
2) How does the creation of variations in a species promote survival?
Solution:
Genetic variations help species adapt to changes in their environment. They play a key role in evolution by affecting how often different traits appear through natural selection. These variations can be crucial for a species’ survival or extinction.
In-text Questions Set-2
1) How do Mendel’s experiments show that traits may be dominant or recessive?
Solution:
Mendel’s experiments with monohybrid crosses showed that traits can be either dominant or recessive. He crossed tall (TT) pea plants with dwarf (tt) pea plants, and all the offspring in the F1 generation were tall.
When Mendel self-pollinated these F1 plants, about 1/4 of the F2 generation were dwarf. This showed that the tall F1 plants carried both tall and dwarf traits. Tallness was dominant over dwarfness, demonstrating that traits can be dominant or recessive.
2) How do Mendel’s experiments show that traits are inherited independently?
Solution:
Mendel’s experiments demonstrated that traits are inherited independently through his dihybrid cross experiment. He used two traits: seed shape and seed color. Yellow (YY) is dominant over green (yy), and round shape (RR) is dominant over wrinkled (rr).
The F2 generation from this cross showed a 9:3:3:1 ratio: 9 plants with round yellow seeds (RRYY), 3 with round green seeds (RRyy), 3 with wrinkled yellow seeds (rrYY), and 1 with wrinkled green seeds (rryy).
Mendel found that round yellow and wrinkled green seeds were the original combinations, while round green and wrinkled yellow were new. In a cross between plants with dominant traits (RRYY) and those with non-dominant traits (rryy), four types of gametes (RY, Ry, rY, and ry) were produced.
This showed that each gamete type segregates independently, with each type appearing in 25% of the gametes.
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?
Solution:
The given information isn’t enough to determine whether blood group A or O is dominant. Blood type A is dominant, while blood type O is recessive. The father’s blood group could be AA (homozygous) or AO (heterozygous), and the mother’s blood group could be OA or OO.
4) How is the sex of the child determined in human beings?
Solution:
In humans, the sex of the child is determined by the male. Males have XY chromosomes, while females have XX chromosomes.
If the male’s X chromosome combines with the female’s X chromosome, the baby will be a girl.
If the male’s Y chromosome combines with the female’s X chromosome, the baby will be a boy.
Exercise Questions
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 makeup of the tall parent can be depicted as
(a) TTWW
(b) TTww
(c) TtWW
(d) TtWw
Solution:
(c) 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 color trait is dominant or recessive? Why or why not?
Solution:
To determine if a trait is dominant or recessive, you need to know the trait’s behavior over at least three generations. Without this information, you cannot identify whether the trait is dominant or recessive.
3) Outline a project which aims to find the dominant coat colour in dogs.
Solution:
Dogs have various genes that determine coat color. There are at least eleven different gene series (A, B, C, D, E, F, G, M, P, S, T) that affect this trait.
A dog inherits one gene from each parent. The dominant gene determines the coat color. For example, in the B gene series, a dog can be either black or brown.
If one parent is homozygous black (BB) and the other is homozygous brown (bb), all their offspring will be heterozygous (Bb). Since black (B) is dominant, all the puppies will be black, though they will carry both B and b alleles.
When two heterozygous (Bb) dogs are bred, their puppies will be:
– 25% homozygous black (BB)
– 50% heterozygous black (Bb)
– 25% homozygous brown (bb)
4) How is the equal genetic contribution of male and female parents ensured in the progeny?
Solution:
In offspring, both parents contribute equally to the genetic makeup by passing on an equal number of chromosomes.
Humans have 23 pairs of chromosomes: 22 pairs are autosomes, and the remaining pair are sex chromosomes (X and Y). Females have two X chromosomes, while males have one X and one Y chromosome.
During reproduction, fertilization occurs when a male gamete (sperm) combines with a female gamete (egg), forming a diploid zygote. This zygote receives an equal contribution of genetic material from both parents: 22 autosomes and one sex chromosome from each parent.