DNA Recombination and Genetic Variation

Questions and Answers

Recombinant DNA molecules with novel sequences

Anywhere in the homologous nucleotide sequences

A heteroduplex joint

Long regions of sequence similarity Signup and view all the answers

Sequence similarity between DNA molecules Signup and view all the answers

New recombinant DNA molecules are generated Signup and view all the answers

Not a single nucleotide is lost or gained Signup and view all the answers

Long regions of sequence similarity Signup and view all the answers

Creating genetic variation Signup and view all the answers

General recombination Signup and view all the answers

To repair DNA replication forks Signup and view all the answers

The exchange of genetic information between chromosomes Signup and view all the answers

It ensures the correct segregation of chromosomes Signup and view all the answers

Increasing genetic variation Signup and view all the answers

Both multicellular and single-celled organisms Signup and view all the answers

They are intimately connected Signup and view all the answers

Study Notes

DNA rearrangements, caused by genetic recombination, create genetic variation by altering the combination of genes and their expression levels.
Genetic recombination consists of two broad classes: general recombination and site-specific recombination.

General recombination (also known as homologous recombination) occurs between a pair of homologous DNA sequences, usually on two copies of the same chromosome.
This process is essential for every proliferating cell, as it repairs DNA replication accidents and ensures accurate chromosome segregation during meiosis.
General recombination involves the crossing-over of chromosomes, resulting in the exchange of genetic information and the creation of new combinations of DNA sequences.
This type of gene mixing is beneficial for evolution and is not confined to multicellular organisms, but is also widespread in single-celled organisms.

Two homologous DNA molecules "cross over" by breaking and rejoining their double helices to form two intact double helices, each composed of parts of the two initial DNA molecules.
The site of exchange can occur anywhere in the homologous nucleotide sequences of the two participating DNA molecules.
At the site of exchange, a strand of one DNA molecule becomes base-paired to a strand of the second DNA molecule, creating a heteroduplex joint.
The heteroduplex region can be thousands of base pairs long, and no nucleotide sequences are altered at the site of exchange.
Despite its precision, general recombination creates DNA molecules of novel sequence, tolerating a small number of mismatched base pairs.