Recombination: An Introduction
Have you ever thought about why children look sometimes similar to their parents or sometimes different? Do you know about linkage and recombination? Linkage is the process of not separating alleles from each other and results in the transfer of combined alleles to the next generation. There are mainly four types of recombination - homologous recombination, heterologous recombination, site-specific recombination, and replicative recombination. There are also many differences between homologous recombination and site-specific recombination.
What is Recombination?
Recombination is defined as the process in which DNA strands are broken, then new strands are produced with different combinations of alleles. It is a process of repairing alleles.
Types of Recombination
There are mainly four types of genetic recombinations. These four types are given below:
Homologous recombination
Nonhomologous recombination
Site-specific recombination
Replicative recombination
What is Homologous Recombination?
Homologous recombination is the recombination of alleles between identical strands of DNA. Here the exchange of genetic material occurs between the same strands or different stands of the same DNA. Recombination helps in repairing genetic material and it also helps in bringing genetic diversity.
What is Non-Homologous Recombination?
In non-homologous recombination, the ligation of genes or alleles occurs without the need for a homologous template. It repairs the break of double-strand DNA, whereas homologous recombination requires a homologous template.
What is Site-Specific Recombination?
Site-specific recombination is defined as the recombination of alleles between segments that have a certain degree of sequence homology. It is also known as conservative site-specific recombination. Here the exchange of alleles or genes takes place between those segments which have a certain degree of sequence homology.
What is Replicative Recombination?
This process is mostly used by transposable elements. In this new copy of segments, DNA is generated. In this, a copy of new transposable elements is formed at the new site on the same chromosome.
Similarities Between Homologous Recombination and Site-Specific Recombination
There are many similarities between homologous and site-specific recombination. These similarities are explained below:
They both are types of recombination
Both types of recombination processes use specific proteins for recombination.
Both processes occur in DNA.
They increase genetic variability between organisms.
Both processes take place in both eukaryotes and prokaryotes.
Difference Between Homologous Recombination and Site-Specific Recombination
There are several differences between homologous recombination and site-specific recombination. Some of the differences are explained below:
Important Questions
1. What is the difference between homologous and non-homologous recombination?
2. What is the purpose of homologous recombination?
Ans: Homologous recombination is used to produce repaired genetic material such as chromosomes, or to prevent the damage of the replication fork and to the maintenance of chromosomes.
3. In which phase homologous recombination occurs?
Ans: Homologous recombination occurs in the S and G2 phases of the cell cycle. It relies on the information present on homologous chromosomes.
Interesting Facts
Genetic recombination occurs in eukaryotes as well as in some prokaryotes.
It occurs naturally in bacteria and viruses too.
It is a powerful tool in genetic engineering.
Key Features
In this article, we discussed recombination, types of recombination, and similarities as well as differences between homologous recombination and site-specific recombination
There are mainly four types of recombination- homologous recombination, nonhomologous recombination, site-specific recombination, and relative recombination
The main difference between homologous recombination and site-specific recombination is that homologous recombination is an exchange of genetic material between the same strand of DNA whereas site-specific recombination between segments of DNA has some degree of analogy.
Practice Questions
What enzyme does homologous recombination?
Why is homologous recombination important in meiosis?
Which protein is important in homologous recombination?
What is homologous recombination and what is its outcome?
What are the steps of homologous recombination?
FAQs on Recombination
1. Explain the steps of homologous recombination.
Homologous recombination is defined as the exchange of genetic material between strands of DNA. It is divided into three steps:
Strand Exchange - It is initiated by a 5’-3’ degradation of one strand at both break ends producing 3’ single-stranded segments. Then 3' end joins with a homologous segment of a sister chromatid to provide a DNA cross-over.
Branch Migration - In branch migration, the heteroduplex region extends.
Resolution - The last step is the resolution. In this, the strands which join two strands are cleaved.
2. What are the different types of linkages?
There are mainly two types of linkages: complete linkage and incomplete linkage.
Complete Linkage - In complete linkage, some genes do not separate from each other, due to a lack of crossing over and transferring together in the next generation. Complete linkage occurs in very few organisms such as drosophila.
Incomplete Recombination - Here complete linkage does not occur, there is a linkage in some genes. The percentage of incomplete linkage is more than 25%.
3. What is the purpose of homologous recombination?
There are several purposes of homologous recombination. Some of the purposes are given below:
It is used for the repair of damaged DNA or chromosomes
It is also used for preventing the demise of damaged replication forks
The homologous combinations are also used for the maintenance of other aspects of chromosome
Sometimes homologous combinations may lead to the undesirable arrangement of DNA
It is also important during mitosis
And for chromosomal pairing.
