GN 301 Module 3: DNA Replication

Nucleotides

joined to each other by the enzyme polymerase

phosphodiester bonds

bonds between nucleotides, created by the enzyme polymerase

Discontinuous DNA synthesis

occurs from the 5 'end to the 3 'end of the parent strand.

Telomerase

an enzyme that can add repetitive DNA sequences to the ends of chromosomes, thereby extending the length of telomeres.

initiation sequence

the sequence necessary for DNA polymerase to synthesize new strands.

Abnormal telomerase activity

contributes to the development of cancer, as it allows cells to continue dividing uncontrollably.

Bidirectional replication

involves replicating DNA in two directions at the same time which results in a leading strand and a lagging strand.

DNA synthesis

During ________, DNA polymerase can only add new nucleotides in the 5 'to 3 'direction of the DNA strand.

RNA primers

the key to initiating DNA synthesis.

Describe the Meselson and Stahl results and conclusion

They grew E coli. in a petri dish in N15 media and watched it grow for a few generations. Then, they transferred cells to N15 media let the E coli. replicate. This allowed them to rule out conservative and dispersive replication.

15 N is ___ than 14N

heavier

Which 3 possibilities did Meselson and Sthal consider?

Conservative, Dispersive, and Semiconservative

What is meant by semiconservative replication?

In this model, the two strands of DNA unwind from each other, and each acts as a template for synthesis of a new, complementary strand. This results in two DNA molecules with one original strand and one new strand.

Define Okazaki fragments and state where they are found.

Okazaki fragments are fragments of DNA that are formed during DNA replication of the lagging strand. Okazaki fragments were discovered by Reiji Okazaki in 1968. During DNA synthesis, DNA polymerase can only add new nucleotides in the 5' to 3' direction of the DNA strand.

Leading vs Lagging strands

The major difference between a lagging and leading strand is that the lagging strand replicates discontinuously forming short fragments, whereas the leading strand replicates continuously

bidirectional replication

Bidirectional replication involves replicating DNA in two directions at the same time which results in a leading strand and a lagging strand.

Why is an RNA primer used in DNA replication?

RNA primers are key to initiating DNA synthesis. They provide the initiation sequence necessary for DNA polymerase to synthesize new strands. The RNA primer is introduced at the template DNA site by primase enzyme on both the leading and lagging strands.

telomeres

the ends of chromosomes

shorten

With each cell division, telomeres ____, and when they become too short, the cell can no longer divide and dies.

Activating telomerase in normal cells could have therapeutic potential for

treating age-related diseases and regenerative medicine.