BIOL 201 Lecture Notes - Lecture 12: Holliday Junction, Genetically Modified Organism, Chromosomal Crossover
Document Summary
The most common form of chromosomal crossover is homologous recombination, where the two chromosomes involved share very similar sequences. Non-homologous recombination can be damaging to cells, as it can produce chromosomal translocations and genetic abnormalities. The recombination reaction is catalyzed by enzymes known as recombinases, such as rad51. The first step in recombination is a double-stranded break caused by either an endonuclease or damage to the dna. The holliday junction is a tetrahedral junction structure that can be moved along the pair of chromosomes, swapping one strand for another. The recombination reaction is then halted by cleavage of the junction and re- ligation of the released dna. Dna contains the genetic information that allows all modern living things to function, grow and reproduce. However, it is unclear how long in the 4-billion-year history of life dna has performed this function, as it has been proposed that the earliest forms of life may have used.