Question

Balbiani discovered special type of chromosome from salivary gland of Chironomus larva, which are recognised by the presence of
A) Bands
B) Loops
C) Both bands and loops
D) None of the above

Answer 1

Hint: Balbiani discovered polytene chromosomes. These chromosomes are large chromosomes which have thousands of DNA strands. They are commonly found in the non dividing cells of salivary glands in insects.

Complete Answer:
- The structure and function of a special chromosome discovered by Balbiani.
- E.G Balbiani in 1881 first discovered the special kind of chromosome called the polytene chromosomes from salivary glands of dipteran flies. Polytene means many strands.
- The polytene chromosomes are produced when repeated rounds of DNA replicate without cell division. As a result, they form a giant chromosome in which many sister chromatids remain fused together. This type of division is called endomitosis.
- Polytene chromosomes at the interphase appear as distinct thick and thin bands and interbands. The dark bands contain more DNA and less RNA whereas the interbands contain more RNA and less DNA.

POLYTENE CHROMOSOME

Thus the correct answer is (A). The special type of chromosomes was recognised by the presence of bands.

Additional Information: The polytene chromosomes are used to identify Chironomid larvae which are difficult to identify. The Karyotypes are used to confirm the presence of specific species and study the genetic diversity.

Note: Polytene chromosomes are giant chromosomes which have light and dark bands. The bands help to identify chromosome mutations. These bands are also used to study the function of genes in transcription.