Question

The lampbrush loops and polytene puffs are
A. Analogous structures
B. Homologous structures
C. Homologous and analogous structures
D. Not related to each other

Answer 1

Hint: Lampbrush chromosomes appear brush-like during their transcription and also this appearance of the structure is peculiar in certain stages of their cell division. Polytene puffs are regions on polytene chromosomes and their appearance is also in a puff a manner for their maximum transcription.

Complete answer: Chromosomes are the string-like structures located in the nucleus of every cell in animals and plants. The chromosomes include DNA and some proteins which help in packing of DNA inside the nucleus. The chromosomes based on their appearance can be identified as lampbrush chromosomes, polytene chromosomes, and supernumerary.
-Lampbrush chromosomes are the largest in size known till now. They are found in many animals except mammals. These chromosomes are best described in oocytes of some animals like tail and tailless amphibians, birds, and insects. It has a longitudinal axis where a number of bead structures called chromosomes are aligned.
-From each chromomere, lateral loops arise. These loops in lampbrush chromosomes are called lampbrush loops. These loops help in the active transcription of RNA. Loop formation reduces the weight of the associated chromomeres showing emerging chromomere material into the lateral strands. These types of chromosomes are seen in the diplotene stage of prophase in meiosis.
-Polytene chromosomes have thousands of DNA strands extending outside forming polytene-like structures. They have many chromatids arranged in a parallel manner. These chromatids have some tightly coiled regions and some loosely coiled regions and thus they appear in bands under a microscope. They are found in the larvae of some dipterans.
-During the development of larva, the polytene chromosomes may show puff like appearance due to their ongoing active transcription of RNA. The chromosomes need uncoiling for their transcription. Balbiani rings are seen when there is the formation of larger puffs. Both chromosomes have similar structures optimal for the active transcription of RNA. Thus, lampbrush loops and polytene puffs have different structure or appearance but the same function. These are analogous structures.
Hence, the correct option is A.

Note: Both types of structures, lampbrush loops, and polytene puffs perform the same function but they have different initial structures. Loops indicate lampbrush chromosomes and thousands of DNA strands extending outside and bands indicate polytene chromosomes. Polytene chromosomes do not always show polytene puffs. Only lampbrush loop structures are ideal for studying the transcription of certain proteins as they have visible genes on loops.