Question

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

Answer 1

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

Complete answer:
In insect polythene chromosomes are usually found in salivary glands and therefore referred as "salivary glands chromosomes". The bands of polytene chromosomes take some enlarged shape and form puffs. In the puff region, chromonemata become uncoil and open to form loops. The loops appear as rings, they are called Balbiani rings. They are formed by DNA, RNA and proteins.

Let us gather information about the options and find the correct answer.
1.Option A: Lampbrush chromosomes are giant and huge chromosomes that occur in the nuclei of oocytes of many vertebrates, such as fishes, amphibians, reptiles and birds during the prolonged diplotene stage of first meiosis. They are made up 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. In lampbrush chromosomes, Balbiani rings are not present there therefore, this is the incorrect option.
2.Option B and C: In human sex is controlled by pair of chromosomes called sex chromosomes, heterosomes or allosomes. There are 23 pairs of chromosomes, out of these presents are 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 controlled by male only. In heterosomes and allosomes, Balbiani rings are not seen to occur, therefore, this is the incorrect option.
3.Option D: In polytene chromosomes, Balbiani rings were first discovered by E.G Balbiani (1881). They are known to occur in dipterans, insects, and some arthropods. Therefore, this is the correct option.

Hence, the correct answer is option (D)

Note: Polytene chromosomes are made up of 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 defined as heterochromatic regions that have small amounts of DNA, large RNA and acidic proteins.