Cope’s rule:  A proposed generalization that individual body size in animals tends to increase during evolution.

TLS Online TPP Program

#Id: 3700

#Unit 2. Cellular Organization

Deletions in two genes, neither of which is lethal by itself, are introduced into the same strain. If the double mutant dies, the strain is called a synthetic lethal. This technique has been used to great effect with yeast, where the isolation of double mutants can be automated. The procedure is called synthetic genetic array analysis (SGA)

TLS Online TPP Program

#Id: 3701

#Unit 2. Cellular Organization

In any particular cell, most genes are expressed at a low level

Only a small number of genes, whose products are specialized for the cell type, are highly expressed.

mRNAs expressed at low levels overlap extensively when different cell types are compared.

The abundantly expressed mRNAs are usually specific for the cell type.

TLS Online TPP Program

#Id: 3702

#Unit 2. Cellular Organization

The proportion of DNA containing protein-coding genes being expressed in a specific cell at a specific time can be determined by the amount of the DNA that can hybridize with the mRNAs isolated from that cell called as RoT analysis

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.