Question

Tell in short about different theories of DNA replication.....

Answer 1

Three Different theories for DNA Replication

Watson and Crick had proposed that in order to copy itself, DNA would have to open down the center, sort of like a zipper coming apart, so that a new DNA strand could be built on top of the exposed strands. Following the rules of complimentary base pairing, adenine would pair with thymine, and cytosine would pair with guanine. This idea was called a template model, since one DNA strand serves as the template for a new one.

Watson and Crick figured that this model would result in two new double strands of DNA, each one with one strand of parent (or template) DNA and one strand of daughter (or newly-synthesized) DNA. They called this the semi-conservative model, because half of the parent DNA was conserved in each new DNA molecule.

Scientists looked at the double helix of DNA and wondered how in the world it could possibly open itself up without getting tangled or torn apart. So they thought up some other ideas about how DNA replication works. One hypothesis, called the dispersive model, suggested that DNA only copied itself for short chunks at a time, producing new strands that alternated parent and daughter DNA. Another idea, called the conservative model, argued that DNA didn't split open at all, but somehow kept the parent strands intact while creating an entirely new and separate copy.

Nobody knew for sure how DNA replication really worked until two scientists named Matthew Meselson and Franklin Stahl devised an ingenious experiment in 1958. They realized that they could test all three models at once by keeping track of what happens to one parental DNA strand as it generates a series of copies.Each model predicts a different distribution of parent DNA following a round of DNA replication. If Meselson and Stahl were able to keep track of parent versus new DNA, they could either support or refute the predictions of the three different models.

Answer 2

In summary, DNA replication is the process of making copies of DNA. DNA replicates by semi-conservative replication, which means that one strand of the parent double helix is conserved in each new DNA molecule. Meselson and Stahl were the scientists who showed that DNA follows the semi-conservative model.