Heredity

1 Marks Question

1. Write scientific name of pea.
2. Scientific name of pea is Pisum sativum.
3. What is monohybrid cross?
4. When a cross is made between two pure individuals having or considering a pair of contrasting characters, the cross is called a monohybrid cross. For example, a cross is made between tall and dwarf pea plants.
5. What is phenotype?
6. The external appearance or expression of an organism is called the phenotype.
7. Write second law of Mendel's related to heredity.
8. Mendel's second law states that although both the contrasting pairs of characters remain together for a long interval of time in the hybrid interval, they are capable to segregate at the time of gamete formation forming a pure gamete.
9. Define genotype. State Mendel's law of dominance.
10. The genetic makeup of an organism of a particular character is called genotype.
    Mendel's law of dominance states that "when a cross is made between two pure individuals having a pair of contrasting characters, only one character appears externally in the first generation called dominant character and another remains hidden as the recessive character".
11. Define continuous variation.
12. Continuous variation is a variation which occurs gradually in the organisms. For example, differences in height, skin colour, eye colour, etc.
13. What is mutation?
14. Sudden, spontaneous and drastic change in the genetic composition of organisms is called a mutation.
15. What is sex linked disease? Write one example of sex linked disease.
16. The disease which is found only either in males or females is called sex-linked disease. For example, hemophilia, colour blindness, and baldness are the diseases which are found in males only, breast cancer is another disease which is found usually in females.
17. What is variation?
18. The physiological difference among the individuals of the same species which gives them individuality is called variation.
19. State Mendel's law of purity of gametes (Law of segregation).
20. Mendel's law of purity of gametes states that although both the contrasting pairs of characters remain together for a long interval of time in the hybrid interval, they are capable to segregate at the time of gamete formation forming a pure gamete.
21. State Mendel's law of independent assortment.
22. Mendel's law of independent assortment states that when two pairs of independent alleles are brought together in the hybrid (F₁) they, at the time of gametes formation, segregate or assort at random and freely.
23. What is hybrid?
24. An individual produced by the cross between two different parents with pure contrasting characters is called a hybrid.
25. Write any two dominant characters seen in human beings.
26. Dominant characters seen in human beings are straight thumb, curly hair, rolling of tongue, dense body hair, etc.
27. What is gene?
28. A gene is a tiny segment of DNA which determines a particular characteristic.
29. What is heredity?
30. Heredity is the transfer of characteristics from one generation to the next generation.