Chapter 4- DNA Replication, Recombination, and Repair

Question 1

3 R’s of DNA fundamental

Answer 1

Replication, Recombination and Repair. Conserved through evolution because these processes act on DNA chains making and breaking of phosphodiester bonds

Question 2

Which agents affect DNA?

Answer 2

DNA is continuously affected by both chemical and physical agents that include activated oxygen species, chemicals in cosmetics and foods and in environment and radiation. Certain chemicals are still being investigated but are generally considered safe in small doses. Recognition and repair of DNA damage to maintain integrity of the genome. Accumulation of mutations lead to cell death, aging and cancer.

Question 3

Template

Answer 3

Provides sequence information for DNA replication. One strand acts as a template to synthesis another complementary strand

Question 4

Semiconservative replication

Answer 4

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.

Question 5

DNA polymerase

Answer 5

Catalyze the addition of mononucleotides to a growing chain. They add nucleotides to an existing primer that provides a 3’ hydroxyl group. DNA polymerases need a primer for this, likely because it improves the overall accuracy of replication

Question 6

Primase

Answer 6

Makes a primer for DNA polymerase out of ribonucleotides. The first few nucleotides are marked for eventual removal because they are ribonucleotides. Their removal leaves a gap that can be resynthesized more accurately because the resynthesis is done by elongation of a longer strand of DNA. When the growing DNA chain is base paired to the template, it serves as a primer for addition of the next nucleotide