Recombination and mobile genetic elements

Question 1

Define genetic recombination

Answer 1

Genetic recombination is also known as homologous recombination. It is defined as the exchange of homologous segments between two DNA molecules. This crossing-over process occurs in higher organisms during meiosis.

Question 2

Describe the mechanisms in which bacteria interchange genetic information

Answer 2

Bacteria can acquire foreign DNA through transformation, through a process known as conjugation(mating) in which DNA is directly transferred from one cell to another via a cytoplasmic bridge and via transduction in which a defective bacteriophage that has erroneously acquired a segment of bacterial DNA rather than the viral chromosome transfers this DNA to another bacterial cell. In all of these processes, the foreign DNA is taken up to the bacterial chromosome via homologous recombination.

Question 3

Briefly explain the holiday model

Answer 3

The holiday model is the proposed model for recombination. The corresponding strands of two aligned homologous DNA duplexes are nicked, and the nicked strands cross over to pair with the nearly complementary strands of the homologous duplex and then the nicks are sealed, thereby yielding a four-way junction known as the Holiday junction. The crossover point can move in either direction in a process known as branch migration, in which the four strands exchange base-pairing partners.