4-4-4 DNA Replication: Copying the Code

Question 1

Date Watson and Crick model was published (1933, 1943, or 1953)

Answer 1

1953

Question 2

2 Questions after Watson and Crick model

Answer 2

how DNA copied its information and how that information was in turn expressed to make a phenotype.

Question 3

Watson and Crick’s hypothesis about DNA replication

Answer 3

one method for DNA replication would be for each strand to serve as a template for the making of the new strands. (Semiconservative replication)

Question 4

semiconservative replication (of DNA)

Answer 4

A DNA molecule is made of two strands. They split apart and each is the template for a new strand. Thus, the replication would produce two DNA molecules. Each would contain one-half of the parental DNA along with a brand new complementary strand. In other words, the new DNA would consist of one new and one old strand of DNA.

Question 5

Matthew Meselson and Franklin W. Stahl (experiment)

Answer 5

bacteria were grown in a Petri dish on a growth medium containing heavy nitrogen. (“Heavy” nitrogen is Nitrogen-15. This isotope of nitrogen has a greater molecular weight than the more common isotope Nitrogen-14.) The bacteria were then moved to a Petri dish with a light (Nitrogen-14) medium. Watson and Crick had predicted that DNA replication was semiconservative. If it was, then the DNA produced by the freshly transferred bacteria grown on light medium would be intermediate between heavy and light. It was!

Question 6

Matthew Meselson and Franklin W. Stahl (accomplishment)

Answer 6

They showed that DNA is replicated using semiconservative replication.

Question 7

The reason for the second G2 phase after the S phase

Answer 7

DNA replication uses lots of energy (in the form of ATP)

Question 8

DNA replication involves many … (3) .

Answer 8

building blocks, enzymes, and a great deal of ATP energy

Question 9

DNA replication rate in humans? In some prokaryotes?

Answer 9

50 nucleotides per second.

500 nucleotides per second.

Question 10

prerequisites for DNA replication

Answer 10

Nucleotides have to be assembled and available in the nucleus. Energy is needed to make bonds between nucleotides.

Question 11

Describe the replication process

Answer 11

DNA enzymes unzip the helix by breaking the hydrogen bonds between bases on each strand. Once the polymerases have opened the DNA molecule, an area known as the replication bubble forms. New nucleotides are placed in the fork between the strands. The new nucleotides link to the corresponding parental nucleotide already there (A with T, C with G). Prokaryotes open a single replication bubble, whereas eukaryotes have multiple bubbles. The entire length of the DNA molecule is replicated as the bubbles meet.