Question

Balbiani rings are the structural features of
(A) Allosomes
(B) Autosomes
(C) Polytene chromosomes
(D) Lampbrush chromosome

Answer 1

Hint: Balbiani rings are the active site of RNA synthesis and help in the functioning of certain tissues such as the salivary glands of insects. Balbiani rings have a rapid turnover of RNA precursors.

Complete step by step answer:
Balbiani rings are the large structure present in the polytene chromosome. They are large puffs and these puffs are used for studying the structure of the active gene and in the synthesis of RNA and protein particles. Polytene chromosomes are large chromosomes. They provide a function in certain tissues such as the salivary glands of insects. Polytene chromosomes contain thousands of DNA strands.

So, the correct answer is ‘Polytene chromosomes’.

E.G Balbiani first reported polytene chromosomes in 1881. Polytene chromosomes increase the volume of the cell nuclei and cause cell expansion. Cells of polytene chromosomes also have multiple copies of genes that permit a high level of gene expression. Polytene chromosomes are also known as Salivary Gland chromosomes as they are found in the salivary glands of the insects. Polytene chromosomes are also present in secretory tissues of dipteran insects.
Puffs are the swelling of bands of the polytene chromosomes. The puffs indicate the site where mRNA synthesis takes place. The formation of puff is known as puffing.

Note: Polytene chromosomes are produced when a repeated round of DNA replication occurs but is not followed up by cell division. In these many sisters, chromatids are fused together. Many thick and thin banding patterns are seen in the Interphase of polytene chromosomes which help in the study of the genes in transcription.