Question

Balbiani rings occur in:
A. Lampbrush chromosomes
B. Heterosomes
C. Allosomes
D. Polytene chromosomes

Answer 1

Hint:Balbiani rings are large puffs of chromosomes, they are diffused uncoiled regions and help in the RNA transcription and protein synthesis. Balbiani rings were first reported by E.G Balbiani in 1881.

Complete answer:
Let us analyse the options and find the correct answer.
>Option A: Lampbrush chromosomes are giant chromosomes found in the nuclei of oocytes of many vertebrates, such as fishes, amphibians, reptiles and birds during the prolonged diplotene stage of first meiosis. They consist of the main axis which have four chromatids and chromonemata of these chromatids give out fine loops at the lateral sides, this gives the appearance of test tube-brush or lampbrush. These loops are the sites of active genes. In lampbrush chromosomes, Balbiani rings are not seen, therefore, this is the incorrect option.
>Option B and C: In human sex is determined by pair of chromosomes called sex chromosomes, heterosomes or allosomes. There are 23 pairs of chromosomes, out of them 22 pairs are autosomes 1 pair is allosomes (in male XY) i.e. in human male. But in females 23 pairs are XX only. So in human sex is determined by male only. In heterosomes and allosomes, Balbiani rings are not seen, therefore, this is the incorrect option.
>Option D: In polytene chromosomes, Balbiani rings were first reported by E.G Balbiani (1881). They are found in dipterans, insects, and some arthropods. Therefore, this is the correct option.
In insect polythene chromosomes are commonly found in salivary glands and therefore referred as “salivary glands chromosomes”. The bands of polytene chromosomes become enlarged and form puffs. In the puff region, chromonemata uncoil and open to form loops. The loops appear as rings, they are called Balbiani rings. They are formed by DNA, RNA and proteins.

Thus, the correct answer is option (D) Polytene chromosomes.

Note:Polytene chromosomes have dark and light bands, Dark bands are Euchromatic in nature and have large amounts of DNA, small amounts of RNA and basic proteins. Light bands are heterochromatic regions that have small amounts of DNA, large RNA and acidic proteins.