Heredity and variation very short answer questions

1. What is meant by characteristics?

It is the detail of appearance or behaviour; in other words, a particular form or a particular function.

Example: Four limbs of human beings is a characteristic and that plant can perform photosynthesis is also a characteristic.

2. Who is known as the father of genetics?

Gregor Johann Mendel is known as the father of genetics.

3. Define chromosome.

Chromosome is a thread-like structure that bears genes and are enclosed within a nucleus. It is composed of DNA and protein.

4. Define variation.

The occurrence of differences among the individuals of a species is called variation.

5. Define a gene.

Gene is a segment of a DNA molecule which carries the code for the synthesis of a specific protein.

6. Define alleles.

Genes which code for a pair of contrasting traits are known as alleles, i.e., they are the different forms of the same gene.

7. Write the expanded form of DNA.

Deoxyribonucleic acid

8. Where is DNA found in a cell? [CBSE (AI) 2015]

DNA is found in genes or chromosomes.

9. What is the function of a gene?

Gene is the carrier of the genetic information from one generation to the next.

10. Who proposed the theory of natural selection?

Charles Darwin proposed the theory of natural selection.

11. Which of the following traits are recessive in pea plant?

Dwarfness, violet flower, wrinkled seed.

Dwarfness and wrinkled seeds are the recessive characters.

12. How many pairs of chromosomes are found in human beings?

23 pairs of chromosomes are found in human beings.

In humans, the gene for black hair colour is B and gene for brown hair colour is b. What will be the hair colour of person having the genetic constitution?

BB
bb
Bb

Black hair,
Brown hair,
Black hair (Heterozygous)

14. Write the names of two types of chromosomes found in an organism.

Autosomes and sex chromosomes

15. How many chromosomes are present in a sperm and an ovum?

Sperm and ovum have 23 chromosomes each.

16. What is a sex chromosome?

The chromosomes which are associated with sex determination of an organism are called sex chromosomes.

17. A woman has only daughters, analyse the situation genetically and provide a suitable explanation.[NCERT Exemplar]

The woman produces ova with ‘X’ chromosome. The man produces sperms with ‘X’ and ‘Y’ chromosome which actually determines the sex of the baby. In this case, everytime the male X chromosome only fuses with the female X chromosome thus producing XX combination.

18. Which sex chromosomes are found in male and female human beings?

Males have one X and one Y-chromosomes, whereas females have two X-chromosomes.

19. Who gave the theory of inheritance of acquired characters?

Lamarck

20. Define mutation.

Sudden changes in the genetic form of an organism which are passed on to the next generation are called mutations. Mutations lead to variations in an organism.

21. What are fossils?

Fossils are the remains or impressions of the dead animals and plants that lived in the past.

22. What is the significance of Archaeopteryx in evolution?

Archaeopteryx provides evidence of evolution of birds from reptiles and its study shows that:

(i) birds and reptiles had a common ancestor.

(ii) birds have evolved from reptiles.

23. Why are acquired characters not inheritable?

Acquired characters are not inherited because they affect the somatic cells and these changes are not incorporated in the chromosomes of cells that will form germ cells.

24. What is genetic drift?

The elimination of the genes of certain traits when a section of a species population migrates or dies due to natural calamity. It alters the gene frequency of the remaining population.

25. How do we know how old a fossil is?

Age of fossils can be estimated by the depth of the layer of rocks in which they are found. Age of fossils can also be detected from the ratio of isotopes in the fossils containing rocks.

26. What is organic evolution?

Evolution is the sequence of gradual changes of the living organisms, which takes place in the primitive organisms over millions of years resulting in the formation of new species.

27. What are the basic events in evolution?

A gradual genetic change in a group of living beings to produce new forms brought about by changes in DNA during reproduction are the basic events in evolution.

28. When a cell reproduces, what happens to its DNA?[CBSE (AI) 2017]

When a cell reproduces, copy of DNA is created.

29. Newly formed DNA copies may not be identical at times. Give one reason.                 [CBSE (AI) 2017]

Newly formed DNA copies may not be identical at times if there is error or inaccuracies in DNA copying.

30. Why is variation important for a species?[CBSE (AI) 2017]

Variation is important for species to survive.