Some people have an allele called Δ32 at the CCR5 locus in which 32 bp are deleted.

CCR5 that plays a role in inflammatory response. Unfortunately, this protein is also a key to human immunodeficiency virus (HIV) infection. The virus binds to a loop of the CCR5 protein and then enters the cell.

The missing part of the gene codes for the loop in the protein to which the virus attaches. 

TLS Online TPP Program

#Id: 4007

#Unit 2. Cellular Organization

Matrix-associated regions (MARs) may be identified by characterizing the DNA retained by the matrix isolated in vivo (left) or by identifying the fragments that can bind to the matrix from which all DNA has been removed (right).

TLS Online TPP Program

#Id: 4009

#Unit 2. Cellular Organization

           

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.