DNA metabolism

Question 1

What is the central dogma to biology?

Answer 1

Flow of genes -> Proteins

Question 2

What are the 3 kinds of DNA replication?

Answer 2

1. Semiconservative
2. Conservative
3. Dispersive

Question 3

Explain the Meselson + Stahl experiment

Answer 3

Growth of e.Coli in heavy isotope N15 only.

Strand of DNA -> CsCl centrifuge density gradient = low density

Same “heavy DNA”, then allowed to replicate in N14

Creates hybrid DNA [N14/N15] -> medium density

Undergoes second replication and forms low density N14 and hybrid

Products: 1/2 N14 low density and 1/2 N15/N15intermediate density

Question 4

What did the Meselson and Stahl experiment prove?

Answer 4

Semiconservative replication

Question 5

What would the products of the Meselson Stahl experiment be if conservative replication took place?

Answer 5

• 1/4 High density [N¹⁵]
• 3/4 Low density [N¹⁴]

Question 6

What would the products of the Meselson Stahl experiment be if dispersive replication took place?

Answer 6

All intermediate density dna! hybrid of [N¹⁴/N¹⁵]