Answer the following questions in one sentence each :

1. Which plant did Mendel choose to perform the experiments to study inheritance ? 

Ans. Mendel chose garden pea plant (Pisum sativum) to perform the experiments to study inheritance. 

2. What is dominant character ? 

Ans. Dominant character is the one which masks or hides its recessive partner. 

3. What is recessive character ? 

Ans. Recessive character is the one which is not exhibited in the next generation. 

4. What is the first filial generation (F1) ? 

Ans. The first generation produced by crossing parents having contrasting characters is called as the first filial generation (F1). 

5. What is second filial generation (F2) ? 

Ans. The generation produced by the self-pollination of F1 plants is called as the second filial generation (F2). 

6. What is embryology ? 

Ans. Embryology deals with the study of development of an organism from an embryo. 

7. What are connecting links ? 

Ans. Organisms which are structurally intermediate between two different groups are called as connecting links. 

8. What are sex-chromosomes ? 

Ans. A pair of chromosomes which decides the sex of the individual is referred to as sex-chromosomes. 

9. What is homozygous ? 

Ans. An organism which can produce similar types of gametes is called homozygous. 

10. What is heterozygous ? 

Ans. An organism which can produce different types of gametes is called heterozygous. 

11. On which fact are the laws for inheritance of traits in human beings based ? 

Ans. The laws for inheritance of traits in human beings are based on the fact that both the mother and father contribute equal quantity of genetic material to the child. 

12. What is a gene ? 

Ans. A fragment of DNA that provides complete information about one protein is referred to as gene for that protein. 

13. Give examples of heterozygous females (XY) and homozygous males (XX). 

Ans. Birds and lepidopterans like moths and butterflies have heterozygous females (XY) and homozygous males (XY). 

14. Give examples where gametes from the female decides the sex. 

Ans. In birds and lepidopterans like moths and butterflies, the gametes from the female decides the sex. 

15. From which group of animals have mammals evolved ? 

Ans. Mammals have evolved from reptiles. 

16. From which group of animals have amphibians evolved ? 

Ans. Amphibians have evolved from fishes. 

17. What do you mean by DNA ? 

Ans. DNA is Deoxyribose Nucleic Acid. It is the genetic material responsible for heredity. 

18. What is the pecularity of DNA structure ? 

Ans. DNA is a double helical structure made up of ribose sugar, phosphate and nitrogen bases. The strands are made up of sugar and phosphate molecules attached alternately. The strands are attached to each other by pairing of nitrogen bases. 

19. Name the scientist who put forth the most popular model of DNA. 

Ans. James Watson and Francis Crick put forth the most popular (Watson and Crick model) of DNA. 

20. What are monohybrid crosses ? 

Ans. Crosses involving only pair of contrasting characters or traits are termed as monohybrid crosses. 

21. What is dihybrid cross ? 

Ans. A cross involving two pairs of contrasting characters is called as a dihybrid cross. 

22. Name some of the vestigial organs in man. 

Ans. Some of the vestigial organs in man are vermiform appendix, ear muscles, wisdom teeth, plica semilunaris (representing nictitating membrane of the eye), coccyx (reduced tail) etc. 

23. In which animals is sex reversal possible ? Ans. Sex reversal is possible in certain fishes, amphibians and birds. 

24. What is the function of caecum and appendix in mammals ? 

Ans. The function of caecum and appendix in mammals is the digestion of cellulose.

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