Principles Of Inheritance And Variation Ques 211
211. The polytene chromosomes were discovered for the first time in
(a) Drosophila
(b) Chironomus
(c) Musca nebulo
(d) Musca domestica
Show Answer
Answer : b
Hints & Solution
(b) Polytene chromosomes are also called giant chromosomes. They consist of numerous parallel identical chromatids due to repeated duplication without division. They were first time observed by Balbiani in the salivary glands of Chironomus. Polytene chromosomes are formed when the products of multiple rounds of S-phase remain tightly associated to form one supersized chromosome. In particular polytene chromosomes are found in a specific subset of endopolyploid cells, which have undergone a variant cell cycle known as the endocycle.
BETA
