Experimental Genetics

Experimental Genetics:

The branch of genetic  which deals with the planning , performing  and interpreting  genetical experiments is called experimental  genetics. Thomas Hunt Morgan is know as father of experimental genetics. He through  of employing  fruitfly  Drosophila melanogaster  as experimental  animals instead of rabbits or mice because  the fly does not demand much care and expensive food articles . Morgan was assisted by his colleagues like Sturtevant, Bridges and Muller. Morgan discovered criss__ cross inheritance, mutability  of genes,  occurrence of genes  in chromosomes, lineage, crossing over and distance between  genes,  chromosome mapping,  etc. He was awarded  Nobal Prize for Physiology  in 1933 for his pioneering work in experimental genetics. 

Drosophila melanogaster as material for Experimental  Genetics:

  Fruitfly  Drosophila  is a small _ sized fly about 2nm size which is found hovering  over ripe fruits like Mango and Banana. It is attached  to yeast cells present on the surface  of the ripe fruits.  In the laboratory the fruitfly  is reared in culture medium containing sooji or ravan ( cream of wheat), molasses,  yeast and agar. The following  factors make Drosophila highly  suitable  for genetic studies.

(i) The fly is quite small in size, but it can be easily examined under a hand lens or low power of microscope.

(ii) The fly shows a number  of externally visible  and easily identifiable  contrasting traits,  which are very important for making  genetic  related  observation.

(iii) A single mating in this fly produces  hundreds of offspring. 

(iv) The fly is harmless  and can be handled  without fear.

(v) Larvae also feed on the same culture medium as  the filies.

 Drosophila is even more suitable than Pea as  experimental  materials  because ,

(i)  It can be easily  reared and bred under laboratory conditions. 

(ii) The fly has a short life span of 10_ 20 days. A new generation can be got every  two weeks. On the other hand pea plant takes a minimum of one season to produce  seeds, which then have to be grown in the next season to check for many phenotypes.

(iii) This fly can be bred throughout  the year so that numerous generations can be obtained in a single  year.

(iv) Females are easily  distinguishable from the males ( in contrast to  bisexual  flowers of pea plant) by the larger body size and presence of ovipositor ( egg laying structure) at the end of abdomen. Because of clear differentiation  of male and female  filies,no selfing is possible at any stage, instead male and female flies of desired  genotypes can  be interbred.

(v) It has a smaller  number ( 4 pairs) of morphologically distinct  chromosomes. 

(vi) Polytene  chromosomes occur in thr salivary  glands of the larva. Polytene  chromosomes can indicate different  types of chromosome aberrations. 

(vii) It has heteromorphic  ( XY) sex chromosomes in the male. The transmission  of heteromorphic  chromosomes can easily  be studied  from one generation  to another. 


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