1. Which of the processes, sexual reproduction or asexual reproduction, brings about maximum variations in the offsprings?
2. Name one variation in humans connected with ears.
3. What constitutes the link between one generation and the next?
4. If the 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?
5. Mendel said that the characteristics or traits of organisms are carried from one generation to the next by internal factors which occur in pairs. What is the modern name for these factors?
6. Some plants occur in one of the two sizes: tall or dwarf. This characteristic is controlled by one pair of genes. Tallness is dominant to dwarfness. Choose suitable letters for this gene pair.
7. What are the chromosomes XY and XX known as?
8. Which of the two, sperm or ovum, decides the sex of the child?
9. State whether the following statement is true or false:
The sex of an infant is not a case of inheritance of characteristics.
10. A new born child has an XY pair of chromosomes. Will it be a baby boy or a baby girl?
11. Which of the following combinations of sex chromosomes produce a male child: XX or XY?
12. Name the first scientist who studied the inheritance of traits from one generation to the next.
13. What type of plants was used by Mendel for conducting his experiments on inheritance?
14. The gene for red hair is recessive to the gene for black hair. What will be the hair colour of a person if he inherits a gene for red hair from his mother and a gene for black hair from his father?
15. What are the four blood groups in humans?
16. Name one reptile in each case where higher incubation temperature leads to the development of: (a) male progeny, (b) female progeny.
17. Fill in the following blanks with suitable words:
(a) Genes always work in...............
(b) In pea plants, the gene for dwarfness is...... whereas that for tallness is..............
(c) Most people have.......... earlobes but some have..... earlobes.
(d) A human gamete contains....... chromosomes whereas a normal body cell has…….. chromosomes in it.
(e) All races of man have..... blood groups.
(J) The............ chromosomes for a........ are XX whereas that for a............. are XY.
18. Which of the following represent tall plants and which represent short plants (or dwarf plants)?
(a) Tt (fa) tt (c) TT
Give reason for your choice (The symbols have their usual meaning).
19. A man having blood group O marries a woman having blood group B and they have a daughter. What will be the blood group of the daughter?
20. (a) Name the scientist who gave the laws of inheritance.
(b) Name an animal in which individuals can change sex. What does this indicate?
21. Explain with an example, how genes control the characteristics (or traits).
22. (a) State one advantage of variation to a species.
(b) What are sex chromosomes? How many sex chromosomes are there? Name them.
23. Explain how, sex is determined in human babies.
24. What do the following symbols used in the topic on heredity represent?
(a) TT (b) tt (c) XX (d) XY
25. (a) What will you get in the F1 and F2 generations in the following cross ?
Pure tall pea plant x Pure dwarf pea plant
(b) Is it an example of monohybrid cross or dihybrid cross?
26. In the F2 generation of a cross, progeny having different traits are produced in the ratio 3:1. State whether it is a monohybrid cross or a dihybrid cross? Give one example of such a cross.
27. (a) What is the genotype of dwarf plants which always produced dwarf offspring?
(b) What is the genotype of tall plants which always produced tall offspring?
(c) What is the genotype of (i) dwarf plants, and (ii) tall plants, whose parental cross always produces tall offspring?
28. (a) If a normal human cell has 46 chromosomes, how many chromosomes will be there in a human (i) sperm cell, and (ii) zygote ? (b) What sizes of plants are produced if both parents have genes Tt?
29. In a human, how many chromosomes are present in:
(a) a brain cell?
(b) a sperm in the testes?
(c) an egg which has just been produced by the ovary ?
(d) a skin cell ?
(e) a fertilised egg?
30. Gregor Mendel's first law of genetics states "Of a pair of contrasted characters, only one can be represented in a gamete by its internal 'factor'.
(a) Give the modern name for this 'factor'.
(b) State where these factors are found in gametes.
31. Does genetic combination of mother play a significant role in determining the sex of a new born baby?
32. Give the contrasting traits of the following characters in pea plant and mention which is dominant and which is recessive:
(a) Yellow seed (b) Round seed
1. Sexual reproduction 4. B 5. Genes 6. Tt 9. False 10. Baby boy 13. Pea plants 14. Black hair 17. (a) pairs (b) recessive ; dominant (c) free ; attached (d) 23; 46 (e) same (/) sex ; female; male 18. Tall plants : Tt and TT ; Short plants : tt 19. Equal chance of having blood group O or blood group B 26. Monohybrid cross 27. (a) tt (b) TT (c) (i) tt (ii) TT 28. (a) (i) 23 (ii) 46 (b) 3 tall plants and 1 dwarf plant 29. (a) 46 (b) 23 (c) 23 (d) 46 (e) 46 30. (a) Genes (b) Chromosomes 31. No, because mother has a pair of X chromosomes. All new born babies will inherit an X chromosome from mother regardless of whether they are baby boys or baby girls. 32. (a) Green seed ; Yellow is dominant; Green is recessive (b) Wrinkled seed ; Round is dominant; Wrinkled is recessive