Cryoelectron microscopy allows examination of hydrated, unfixed, and unstained specimens in the TEM by maintaining them at -196oC (liquid nitrogen).

TLS Online TPP Program

#Id: 3703

#Unit 2. Cellular Organization

Highly repetitive DNA (or satellite DNA) has a very short repeating sequence and no coding function.

Satellite DNA is often the major constituent of centromeric heterochromatin

TLS Online TPP Program

#Id: 3704

#Unit 2. Cellular Organization

TLS Online TPP Program

#Id: 3705

#Unit 2. Cellular Organization

Many genes are arranged along the chromosomes in groups of related genes. These groups are called gene clusters. Examples of gene clusters are the globin gene family.

TLS Online TPP Program

#Id: 3706

#Unit 2. Cellular Organization

When a genome contains a cluster of genes with related sequences, mispairing between nonallelic loci can cause unequal crossing over. This produces a deletion in one recombinant chromosome and a corresponding duplication in the other.

TLS Online TPP Program

#Id: 3707

#Unit 2. Cellular Organization

Thalassemias result from occurrence of unequal crossing that reduce or prevent synthesis of either a- or b-globin

TLS Online TPP Program

#Id: 3708

#Unit 2. Cellular Organization

Different thalassemias are caused by various deletions that eliminate a- or b-globin genes. The severity of the disease depends on the individual deletion.