1-Give application of genetics in plant improvement.
- What is genetic variability? Give its importance.
- What is gene mutation? Give its types.
- Write note on genetic recombination.
- What are mutagens? Give its types.
- Write note on selection.
- Write note on hybridization.
- What is plant breeding? Give its procedure and techniques.
- How is the new variety released? Give its rules.
1-What is hybridization? Give it uses.
Ans: It is a traditional technique. The crossing of different varieties of plants specie is called hybridization. Hybridization is used to produce plants with desirable traits. Vegetative propagation is performed on hybrid plants. It produces large number of identical plants with these traits.
- What is meant by genetic variability?
Ans: The amount by which individuals in a population differ from one another due to their genes, rather than their environment is called genetic variability.
- Give importance of genetic variability.
Ans: Genetic variability has great importance for the survival of an species. Low genetic variability can put the survival of specie in danger. For example. the Irish potato famine occurred due to low genetic variability for potatoes. Thus single fungus destroyed all the same crops of potato.
- Differentiate between Germline Mutations and Somatic Mutations.
Ans: Germline mutations can be passed on to descendants. The somatic mutations cannot be transmitted to descendants in animals.
- What are neutral mutation?
Ans: Neutral mutations: Neutral mutations are defined as mutations whose effects do not influence the fitness of either the species or the individuals of the species. These can accumulate over time due to genetic drift. DNA repair is able to revert most changes before they become permanent mutations. Therefore, majority of mutations have no significant effect. Man} organisms have mechanisms for eliminating permanently mutated somatic cells.
6-Differentiate between Splice site and frameshift mutation Ans: In case of Splice site mutation. the coding region of a gene may alter splicing of the mRNA (splice site mutation). Frameshift mutations cause a shift in the reading frame.
7-What are Amplifications?
Ans: Amplifications (or gene duplications) leading to multiple copies of chromosomal regions. It increases the dosage of the genes located within them.
8-What are Amormphic mutations or Loss-of-function mutations?
Ans: These are the result of gene product having less or no function. When the allele has a complete loss of function (null allele) it is often called an amorphic mutation. Phenotypes associated with such mutations are most often recessive.
9-What are Neomorphic mutations or Gain-of-function mutations?
Ans: These change the gene product such that it gains a new and abnormal function. ‘these mutations usually have dominant phenotypes. These are also called a neomorphic mutation.
10-What are induced mutaiton?
Ans: The mutations caused by mutagens are called induced mutations: Induced mutations may be caused by chemicals like Nitrosoguanidine (NTG) or by radiation like ultraviolet radiations.
11-What is genetic recombination?
Ans: Genetic recombination is the transmission-genetic–process by which the combinations of alleles observed at different loci in two parental individuals become shuffled in offspring.
12-Differentiate between Crossing over and Independent assortment.
Ans: The recombination via intra-chromosomal recombination is called crossing over). The inter-chromososomal recombination is called independent assortment.
13-What is selection? Give its types.
Ans: The process by which certain traits or gene are selected due to some environmental advantage is called selection. Selection is classified into natural and artificial selection.
14-What are the advantages of selection?
Ans: In the context of evolution, certain traits or alleles of a
species may be subject to selection. Under selection, individuals with advantageous or “adaptive” traits tend to be more successful. They contribute more offspring to the succeeding generation than others do. The offspring will inherit those traits from their parents. Therefore, selection can increase the prevalence of certain traits.
15- Give conditions for selection.
Ans: Selection occurs only when the individuals of a population are diverse in their characteristics. In the absence of individual variation, or when variations are selectively neutral, selection does not occur.
16-What is Stabilizing and Disruptive selection?
Ans: Stabilizing selection favors individuals with intermediate
characteristics. Disruptive Selection favors those with extreme characteristics. Directional Selection occurs when characteristics lie along a phenotypic spectrum and the individuals at one end are more successful.
17-What is Mechanisms of selection
Ans: Distinct from patterns of selection are mechanisms of
selection: for example. disruptive selection often is the result of disassortative sexual selection. Similarly balancing selection may result from frequency-dependent selection and overdomiance
18-What are 1nterspecific, Intra-specific and Intergeneric hybrids?
Ans: Hybrids between different species within the same genus are
called interspecific hybrids or crosses. Hybrids between different sub-species within a species are called ultra-specific hybrids. Hybrids between different genera are called intergeneric
19-What is meant by plant breeding?
Ans: Plant breeding is the • purposeful manipulation of plant
species in order to create desired genotypes and phenotypes
for specific purposes.
20-What is meant by Heterosis or hybrid vigor.
Ans: In 1908, George Harrison Shull described heterosis or
hybrid vigor. Heterosis describes the tendency of the progeny of a specific cross to outperform both parents. The detection of the usefulness of heterosis for plant breeding has lead to the development of inbred lines. Maize was the first species in which heterosis was used to produce hybrids.
21-What are Somatic hybridization?
Ans: Hybrids may also be produced by a technique called protoplast fusion. In this case protoplasts are fused, usually in an electric field. Cell fusion may lead to nuclear fusion. It produces an amphi-diploid somatic hybrid cells. Fusion products of closely related but sexually incompatible plants have been grown to flowering plants.
22-Define plant variety.
Ans: A population of plants that differ consistently from the typical form of the species. occurring naturally in a geographical area is called plant variety.