S7 DNA Structure and Replication

Question 1

What is a DNA nucleic acid made up of?

Answer 1

Deoxyribose sugar, phosphate group, and a nitrogenous base (A, T, C or G)

Question 2

What is a RNA nucleic acid made up of?

Answer 2

Ribose sugar, phosphate group and a nitrogenous base (A, U, C or G)

Question 3

What is heterochromatin?

Answer 3

DNA wound tightly around histone proteins forming a solenoid shape. Prevents gene expression as can’t “get to” bases.
Looks darker on a micrograph.

Question 4

What is euchromatin?

Answer 4

Still wound around histone proteins but looks like “beads on string”. When gene expression can occur as bases can be accessed. Looks lighter on a micrograph.

Question 5

Which direction does DNA polymerase work in?

Answer 5

5’ to 3’

Question 6

What are Okazaki fragments?

Answer 6

As DNA polymerase works in 5’ to 3’ direction, when DNA helical unwinds the helix more, DNA polymerase unbinds from lagging strand and rebinds, this causes “gaps” between strands of DNA called, Okazaki fragments

Question 7

How are Okazaki fragments joined together?

Answer 7

By DNA ligase

Question 8

How does DNA polymerase initially bind?

Answer 8

An RNA primer is laid down at the 5’ exposed end, to which DNA polymerase can bind

Question 9

Which bases are pyrimidines? And how many “rings” do they have?

Answer 9

T, U and C

1 ring

Question 10

Which bases are purines? And how many “rings” do they have?

Answer 10

A and G

2 rings

Question 11

What is the structure of the DNA double strand?

Answer 11

1. Right-handed double helix

2. Complementary and anti-parallel strands