Polytene chromosomes are formed when the products of multiple rounds of S-phase remain tightly associated to form one supersized chromosome. … We also note that polytene chromosomes can form in cells that undergo transient nuclear envelope breakdown without subsequent chromosome separation (Cantero et al.
What is called giant chromosome?
Polytene chromosomes are large chromosomes which have thousands of DNA strands. They provide a high level of function in certain tissues such as salivary glands of insects. Polytene chromosomes were first reported by E.G.Balbiani in 1881.
Which is the largest chromosome?
Chromosome 1 is the largest human chromosome, spanning about 249 million DNA building blocks (base pairs) and representing approximately 8 percent of the total DNA in cells.
Who discovered giant chromosome?
They were first observed in 1881 by E.G. Balbiani in Chironomus and were studied by Korschelt (1884) and Corney (1884). Heitz and Bauer in 1933 studied these giant chromosomes in Bibio hortulanus larvae, while Painter (1933) described them in salivary glands of Drosophila.
What are Balbiani rings?
Balbiani rings are exceptionally large puffs on the polytene chromosomes in the dipteran Chironomus tentans. These puffs are particularly well suited for studies of the structure of active genes and the synthesis and transport of specific RNA-protein (RNP) particles.
What is a Chromonemata?
Definition of ‘chromonemata’
1. the coiled mass of threads visible within a nucleus at the start of cell division. 2. a coiled chromatin thread within a single chromosome.
Do humans have polytene chromosomes?
While polytene chromosomes are most frequently found in insects, they are critical in diverse organisms from ciliates to plants to humans, and they play important roles in disease progression.
Which animal has the highest number of chromosomes?
The mitotic and meiotic chromosomes of the semiaquatic rodent Ichthyomys pittieri (Rodentia, Cricetinae) from Venezuela were analyzed by means of conventional staining and several banding techniques. The diploid chromosome number of this rare species is 2n = 92, which is the highest value known for mammals.