DNA Recombination and Genetic Variation

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Questions and Answers

What is the outcome of general recombination between two homologous DNA molecules?

Recombinant DNA molecules with novel sequences (correct)

Altered nucleotide sequences at the site of exchange

Loss or gain of nucleotides at the site of exchange

No change in DNA molecules' sequences

Where can the site of exchange occur in general recombination?

Anywhere in the homologous nucleotide sequences (correct)

Only at specific locations in the DNA molecule

Only at the ends of chromosomes

Only in certain types of cells

What is formed at the site of exchange in general recombination?

A triplet code

A single-stranded DNA molecule

A heteroduplex joint (correct)

A double helix

What is required for the formation of a long heteroduplex joint?

Long regions of sequence similarity Signup and view all the answers

What is the mechanism of general recombination based on?

Sequence similarity between DNA molecules Signup and view all the answers

What is the result of general recombination in terms of DNA sequence?

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

How precise is the cleavage and rejoining of DNA molecules in general recombination?

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

What is necessary for the recognition of homologous regions in general recombination?

Long regions of sequence similarity Signup and view all the answers

What is the primary outcome of DNA rearrangements?

Creating genetic variation Signup and view all the answers

What is the term for genetic exchange between a pair of homologous DNA sequences?

General recombination Signup and view all the answers

What is the primary function of general recombination in proliferating cells?

To repair DNA replication forks Signup and view all the answers

What is the result of crossing-over during meiosis?

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

Why is general recombination essential for accurate chromosome segregation during meiosis?

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

What is the evolutionary benefit of general recombination?

Increasing genetic variation Signup and view all the answers

In which type of organisms is general recombination widespread?

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

What is the relationship between DNA replication and general recombination?

They are intimately connected Signup and view all the answers

Study Notes

DNA Recombination

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

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.

Characteristics of General Recombination

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.

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Description

Learn about DNA rearrangements and genetic recombination, including general recombination and site-specific recombination, and their impact on genetic variation.