User:Chandu/Sandbox

POLYTENE CHROMOSOME

INTRODUCTION;

Polytene chromosome is a type of gaint chromosome.First it was found in the salivary glands of drosophila malanogaster,by a scientist balbiani.

it is observed in the interphase stage. it is also known as salivary gland chromosome,because it is observed in the salivary glands of the drosophila.

STRUCTURE OF POLYTENE CHROMOSOME;

Polytene means many thread like structures.The chromosomes are arranged in thread like structures.

it consists of four pairs of chromosomes.Three pairs are long whereas fourth one is short and almost present inside the centromere.

chromosomes consists of dark and light bands.Based on the number of bands present in an organism we can identify the spp.

on the surface of the chromosome ring like structures will be presnt which is known as balbiani rings.These are also known as

chromosomal puffs.These puff like structures are due to the presence of high content of DNA.These chromosomes are found due to multiple

replications of DNA,when DNA undergoes replication the newly formed DNA strand will not be seperated by the template strand and forms

continious thread like structure. so,gaint chromosomes are formed due to the multiple replication of DNA.After observing in drosophila

it was observed in many algae,higher plants etc..,

IMAGE OF POLYTENE CHROMOSOME;

https://www.google.co.in/search?q=polytene+chromosome&client=ubuntu&channel=fs&biw=1301&bih=671&source=lnms&tbm=isch&sa=X&ved=0CAcQ_AUoAWoVChMIrergot2ZyQIVJdumCh3bhgKt#imgrc=U-c9Z11RecFLEM%3A

POLYTENE CHROMOSOME VIDEO

https://www.youtube.com/watch?v=Mkk1WKGvMKk

SIGNIFICANCE;

Endomitosis

DNA replication

RNA synthesis

For spp.identification

For rapid growth