Q. Inbreeding is carried out in animal husbandry because it
(a) increases vigour (b) improves the breed
(c) increases heterozygosity (d) increases homozygosity
Ans. (d) increases homozygosity
Inbreeding increases homozygosity, i.e., state of possessing two identical alleles, one inherited from each parent. It is necessary if we want to evolve a pure line in any animal.
Inbreeding exposes harmful recessive genes that are eliminated by selection. It also helps in accumulation of superior genes and elimination of less desirable genes.
Q. The biggest constraint of plant breeding is
(a) Availability of desirable gene in the crop and its wild relatives
(b) Infrastructure
(c) trained manpower
(d) transfer of genes from unrelated sources
Ans. (a) availability of desirable gene in the crop and its wild relatives
Breeding (conventional) is often constrained by the availability of limited number of disease resistant genes that are present and identified in various crop varieties or wild relatives.
Q. How is a somatic hybrid different from a hybrid?
Ans. Somatic hybrids are obtained by uniting protoplasts from two different varieties of plants and then further cultured to form a novel plant. Compatibility between two plants is not a limitation. Any two protoplasts can be united whereas hybrids are obtained by crossing two selected parent plants of opposite sex. Many times compatibility is a limitation for breeding.
Q. “Give me a living cell of any plant and I will give you a thousand plants of the same type.” Is this only a slogan or is it scientifically possible? Write your comments and justify them.
Ans. It is scientifically possible to grow thousand plants from a living cell of any plant and this process is called micropropagation. The property of plant cells that helped them to grow into a new plant is totipotency. Micropropagation is the use of plant cell culture to regenerate large number of plants. This results in genetically identical plants and is also called clonal propagation. Hence, the desirable characters are kept constant for many generations.
Micropropagation is widely used in forestry and in floriculture. Plants can be obtained throughout the year under controlled conditions.
Class 12 Biology NCERT Exemplar Problems:
NCERT Exemplar book for class 12 Biology consists of a collection of conceptual questions which are designed purely to check a student’s understanding about the various concepts and theories explained in the subject. These problems form the best practice source to prepare effectively for board exams and the medical entrance tests.
Here, we are providing the NCERT Exemplar Problems for Class 12 Biology chapter - Strategies for Enhancement in Food Production, in the PDF form which students may download and solve them to analyse their preparedness for the exams.
Main topics discussed in Class 12 Biology, Chapter 9- Strategies for Enhancement in Food Production, are:
- Animal husbandry
- Plant breeding
- Single cell proteins
- Tissue culture.