Morgan found the fruit fly Drosophila melanogaster very suitable for his genetic studies. Read the following statements about these flies:
A. The flies could be grown on simple synthetic medium in the laboratory.
B. The flies complete their life cycle in a short time.
C. A single mating could produce a large number of progeny flies.
D. The male and female flies are easily distinguishable.
E. The flies have very few types of hereditary variations that can be seen with low power microscopes.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → A, B, C and D only
Thomas Hunt Morgan tested the chromosomal theory of inheritance on the fruit fly Drosophila melanogaster. A good organism for genetic work must be easy to keep, breed quickly, give many offspring, have easily told sexes and show many visible variations.
A. The flies could be grown on simple synthetic medium in the laboratory. — True. The flies are cheap and easy to keep, since they grow on a simple synthetic medium.
B. The flies complete their life cycle in a short time. — True. Their life cycle is complete in about two weeks, so many generations can be studied in a few months.
C. A single mating could produce a large number of progeny flies. — True. A large number of offspring from one cross gives reliable ratios.
D. The male and female flies are easily distinguishable. — True. There is a clear difference between the sexes, which helps in setting up crosses and in studying sex-linked genes.
E. The flies have very few types of hereditary variations that can be seen with low power microscopes. — False. The book says the fly has many types of hereditary variations that can be seen with low power microscopes. Very few variations would make it a poor choice for genetic studies.
NCERT Extract:
Chromosomal Theory of Inheritance – “… Morgan worked with the tiny fruit flies, Drosophila melanogaster (Figure 4.10), which were found very suitable for such studies. They could be grown on simple synthetic medium in the laboratory. They complete their life cycle in about two weeks, and a single mating could produce a large number of progeny flies. Also, there was a clear differentiation of the sexes – the male and female flies are easily distinguishable. Also, it has many types of hereditary variations that can be seen with low power microscopes.”