TLS Online TPP Program

#Id: 4011

#Unit 2. Cellular Organization

A surprising feature is the lack of conservation of sequence in MAR fragments. They are usually 70% A-T rich. cis-acting sites that regulate transcription are common, as are 5’ introns, and a recognition site for topoisomerase II is usually present in the MAR.

TLS Online TPP Program

#Id: 4016

#Unit 2. Cellular Organization

The nuclear matrix and chromosome scaffold consist of different proteins, although there are some common components. Topoisomerase II is a prominent component of the chromosome scaffold, and is a constituent of the nuclear matrix, suggesting that the control of topology is important in both cases.

SATB1, is a protein that appears to regulate the association of MARs with the matrix in order to regulate transcription of genes in the vicinity of the MAR.

TLS Online TPP Program

#Id: 4017

#Unit 2. Cellular Organization

Chromosomes occupy chromosome territories in the nucleus and are not entangled with each other.

Heterochromatic regions, silenced genes, and gene-sparse regions of chromosomes are typically localized to the nuclear periphery.

TLS Online TPP Program

#Id: 4020

#Unit 2. Cellular Organization

Local genome alteration, termed kataegis involves activation-induced deaminase (AID)

Chromothripsis entire chromosomes or large parts thereof are shattered (thripsis in Greek means “shattering”) and stitched together again in what appears to be a random manner, leading to dozens or sometimes even hundreds of rearrangements.

TLS Online TPP Program

#Id: 4021

#Unit 2. Cellular Organization

Active genes are often found at the borders of chromosome territories, and active genes from several chromosomes may cluster in inter-chromosomal territories that are enriched in transcription machinery.

TLS Online TPP Program

#Id: 4023

#Unit 2. Cellular Organization

In most regions, the fibers are much less densely packed than in the mitotic chromosome. This material is called euchromatin. It has a relatively dispersed appearance in the nucleus and occupies most of the nuclear region.