Our ancestors knew about the inheritance of characters and variations because- (1) They selectively breed plants and animals and selected for organisms that possessed desirable characters. (2) They introduced mutations (3) They performed natural hybridisation (4) All of the above

    

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Our ancestors knew about the inheritance of characters and variations because-

(1) They selectively breed plants and animals and selected for organisms that possessed desirable characters.

(2) They introduced mutations

(3) They performed natural hybridisation

(4) All of the above

Answer:

(1) They selectively breed plants and animals and selected for organisms that possessed desirable characters.

Classical plant breeding involves crossing or hybridisation of pure lines,

followed by artificial selection to produce plants with desirable traits of higher

yield, nutrition and resistance to diseases.

👉Traditional hybridisation procedures used in plant and

animal breeding, very often lead to inclusion and multiplication of

undesirable genes along with the desired genes.

👉The techniques of genetic

engineering overcome this limitation and allows us

to isolate and introduce only one or a set of desirable genes

👉Artificial hybridisation is one of the major approaches of crop

improvement programme. In such crossing experiments it is important

to make sure that only the desired pollen grains are used for pollination

and the stigma is protected from contamination (from unwanted pollen).

This is achieved by emasculation and bagging techniques.

👉MENDEL’S LAWS OF INHERITANCE

It was during the mid-nineteenth century that

headway was made in the understanding of

inheritance. Gregor Mendel, conducted

hybridisation experiments on garden peas for

seven years (1856-1863) and proposed the

laws of inheritance in living organisms.

👉Hybridisation experiment carried out by

Mendel where he crossed tall and dwarf pea

plants to study the inheritance of one gene

👉The technique of DNA Fingerprinting was initially developed by Alec

Jeffreys. He used a satellite DNA as probe that shows very high degree

of polymorphism. It was called as Variable Number of Tandem Repeats

(VNTR). The technique, as used earlier, involved Southern blot

hybridisation using radiolabelled VNTR as a probe. It included

(i) isolation of DNA,

(ii) digestion of DNA by restriction endonucleases,

(iii) separation of DNA fragments by electrophoresis,

(iv) transferring (blotting) of separated DNA fragments to synthetic

membranes, such as nitrocellulose or nylon,

(v) hybridisation using labelled VNTR probe, and

(vi) detection of hybridised DNA fragments by autoradiography

👉Consequently, after hybridisation with VNTR probe, the

autoradiogram gives many bands of differing sizes.

👉Interspecific hybridisation: In this method, male and female animals

of two different related species are mated. In some cases, the progeny

may combine desirable features of both the parents, and may be of

considerable economic value, e.g., the mule

👉between individuals of the same breed but having no

common ancestors for 4-6 generations (out-crossing) or 

between

different breeds (cross-breeding) or

 different species (inter-specific

hybridisation).

👉The main steps in breeding a new genetic variety of a crop are –

(i) Collection of variability:germplasm

collection.

(ii) Evaluation and selection of parents:

The selected plants are multiplied and used in the process of

hybridisation. Purelines are created wherever desirable and possible

(iii) Cross hybridisation among the selected parents

(iv) Selection and testing of superior recombinants:

(v) Testing, release and commercialisation of new cultivars:

👉The conventional method of breeding for disease

resistance is that of hybridisation and selection. It’s steps are essentially

identical to those for breeding for any other agronomic characters such

as high yield.

👉Some crop varieties bred by hybridisation and selection, for

disease resistance to fungi, bacteria and viral diseases