Question

The fruit fly Drosophila melanogaster was found to be very suitable for experimental verification of chromosomal theory of inheritance by Morgan and his colleagues because

• A. It completes life cycle in about two weeks.
• B. It reproduces parthenogenetically.
• C. A single mating produces two young flies.
• D. None of the above.

Answer 1

The correct option is A It completes life cycle in about two weeks.

Drosophila was found suitable as experimental material because of the following reasons:

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

(ii) The fly has a short life span of about two weeks. The fruit fly can be bred throughout the year so that numerous generations can be obtained in a single year instead of one as in the case of Pea.

(iii) A single mating produces hundreds of offsprings.

(iv) Females are easily distinguishable from males by the larger body size and presence of ovipositor (egg-laying structure).

(v) The animal shows a number of externally visible and easily identifiable contrasting traits.

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

(vii) Polytene chromosomes occur in the salivary glands of the larva. Polytene chromosomes can be used to study different types of chromosome aberrations.

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

So, the correct answer is 'It completes life cycle in about two weeks