What is Chromocenter in polytene chromosome?

polytene chromosome chromocentre. Definition: A region at which the centric regions of polytene chromosomes are joined together.

What is meant by chromocenter?

: a densely staining aggregation of heterochromatic regions in the nucleus of some cells.

What are the roles of Interbands in polytene chromosome?

The interbands are involved in the interaction with the active chromatin proteins, nucleosome remodeling, and origin recognition complexes. Their primary functions are: to act as binding sites for RNA pol II, to initiate replication and, to start nucleosome remodeling of short fragments of DNA.

Which region of the polytene chromosome is transcriptionally active?

The band/interband pattern of polytene chromosomes is constant. The interband regions that are the transcriptionally active sites on the polytene chromosomes can form an expanded state known as puffs, which are the sites where RNA is being synthesized.

What is the function of Karyosome?

The karyosome or karyosphere is particularly known for its role in oogenesis. It seems to form at the diplotene stage, or in the first meiotic prophase. It is formed when all chromatin material form together to make a mass before the beginning of the first meiotic division.

What is Chromonemata in biology?

Hint: Chromonemata is also known as chromonema. It is present in the chromosomes. They are present in the matrix of the chromosome. Complete answer: The chromosomes are the highly coiled structure present in the nucleus of the Eukaryotic cell.

What is the function of euchromatin and heterochromatin?

Heterochromatin maintains the structural integrity of the genome and allows the regulation of gene expression. Euchromatin allows the genes to be transcribed and variation to occur within the genes.

How does euchromatin and heterochromatin affect gene expression?

Genetic and cytological evidence indicates that interaction between euchromatic genes and heterochromatin can cause gene silencing. Silenced genes, they discovered, are far closer to heterochromatin than expressed genes, indicating that silenced genes interact with heterochromatin while expressed genes do not.

What does transcriptionally active mean?

Term: transcriptionally active chromatin. Definition: The ordered and organized complex of DNA and protein that forms regions of the chromosome that are being actively transcribed.

Why is euchromatin more transcriptionally active?

The two types of chromatin, heterochromatin and euchromatin, are functionally and structurally distinct regions of the genome. Euchromatin, on the other hand, is less condensed, more accessible, and therefore transcriptionally active (Hennig 1999).

What is the role of chromocenters in DNA?

Chromocenters show DNA methylation and histone methylation on H3K9/H4K20, epigenetic modifications associated with chromatin compaction and transcriptional repression ( Saksouk et al. 2015; Nishibuchi and Déjardin 2017 ). Much like pericentromeric satellite DNA, the role of chromocenters as a cytological structure has also remained obscure.

Is the centromere part of the chromocenter?

The centromere as well as the pericentromeric repeats, which constitute the chromocenter, are highly divergent with regard to size, sequence and protein composition even in very closely related species ( 8, 24, 25 ).

What is the function of the interphase chromocenter?

During interphase centromeres often coalesce into a small number of chromocenters, which can be visualized as distinct, DAPI dense nuclear domains. Intact chromocenters play a major role in maintaining genome stability as they stabilize the transcriptionally silent state of repetitive DNA while ensuring centromere function.

How is chromocenter formation mediated by a modular network?

Here we show that chromocenter formation is mediated by a ‘modular’ network, where associations between two sequence-specific satellite DNA-binding proteins, D1 and Prod, bound to their cognate satellite DNAs, bring the full complement of chromosomes into the chromocenter.