Question

Holiday junction (HJ) is a very important mechanism for natural DNA recombination. HJ catalyzes DNA recombination between _________ using a special protein complex.

Select one:

a. two dsDNA

b. one dsDNA and one ssDNA

c. two ssDNA

d. All of these

e. None of these

Answer 1

Holiday junction (HJ) is a very important mechanism for natural DNA recombination. HJ catalyzes DNA recombination between _________ using a special protein complex.

Answer- two dsDNA

During genetic recombination, the formation of X shaped structure for the exchange of genetic material is called Holiday junction. The two dsDNA molecules form an X shaped structure and become four strands.

Genetic recombination can be defined as the recombination of DNA. This can be of two types- Homologous and site-specific recombination.

In Homologous recombination, the genetic exchange takes place between homologous chromosomes or DNA sequences. It is also called general recombination. This recombination is involved in meiotic cross over in eukaryotes and also in integration of acquired DNA in prokaryotes by transduction, conjugation and transformation.

Robin Holliday in 1964 gave the scheme of homologous recombination. This model gave the explanation of recombination between two homologous DNA molecules. Formation of heteroduplex occurs and their is an exchange of polynucleotides segment between the two homologous molecules.

For the formation of Holliday junction, two homogous DNA pairs and endonuclease makes a nick on two strands of DNA.

The DNA strands are displaced and later ligated. Once they are ligated we get a heteroduplex called Holliday junction.

Holliday model Date Page A B 54 3+ 3' 3' 5' 3' b I Endonuclease nicking A B A b 1 Strand displacement. А B to ligation A B Holliday junction a 5