The SL RNA provides an exon that is connected to the first exon of an mRNA by trans-splicing. The reaction involves the same interactions as nuclear cis splicing but generates a Y-shaped RNA instead of a lariat.

TLS Online TPP Program

#Id: 3697

#Unit 2. Cellular Organization

Most known genetic defects in human genes are due to point mutations. The majority directly affect the protein sequence

TLS Online TPP Program

#Id: 3698

#Unit 2. Cellular Organization

Deletion appears to have no effect when genes are present in multiple copies called as gene redundancy

TLS Online TPP Program

#Id: 3699

#Unit 2. Cellular Organization

Genetic redundancy means that two or more genes are performing the same function and that inactivation of one of these genes has little or no effect on the biological phenotype

Redundancy seems to be widespread in genomes of higher organisms

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