DNA Structure and Function

Question 1

What are the four base pairs?

Answer 1

Thymine, Guanin, Adenine, Cytosine

Question 2

What are Chargaffs Rules?

Answer 2

Different species have different amounts of nitrogensous bases; amounts of A&T and G&C are roughly the same amounts.

Question 3

Why does the double helix run antiparallel?

Answer 3

One is upside down compared to the other. One runs 5’ to 3’, the other 3’ to 5’.

Question 4

How many hydrogen bonds do A and T form?

Answer 4

2

Question 5

How many hydrogen bonds do C and G form?

Answer 5

3

Question 6

What are histones?

Answer 6

Proteins around which DNA wraps itself to form nucleosomes. Histones are positively charged because DNA is negatively charged. Help prevent DNA from untangling.

Question 7

What is a nucleosome?

Answer 7

About 150 DNA basepairs wrapped around a histone.

Question 8

What bonds do nucleic acids use?

Answer 8

Glycosodic

Question 9

In which direction is the leading strand replicated?

Answer 9

5’ to 3’

Question 10

In which direction is the lagging strand replicated?

Answer 10

5’ to 3’ in Okazaki fragments.

Question 11

What is on the 3’ of a DNA strand thats important?

Answer 11

A free 3’ hydroxyl group for RNA primase to attach.

Question 12

What are the 7 main enzymes associated with DNA replication?

Answer 12

Helicase; topoisomerase; single-strand binding proteins; RNA primase; DNA polymerase I and III; DNA ligase

Question 13

What does the enzyme helicase do?

Answer 13

UNZIPPING ENZYME. Unwinds original DNA by breaking hydrogen bonds holding them together.

Question 14

What does enzyme topoisomerase do?

Answer 14

Prevents super coiling of DNA double helix AHEAD OF replication fork.

Question 15

What is a telomere?

Answer 15

Six base pair sequence at ends of linear chromosomes. Code for nothing. Get shorter as cell divides (aging). Maintained by telomerase.

Question 16

What is the enzyme telomerase?

Answer 16

Maintains telomeres. Not generally active in adults.

Question 17

What do the enzymes called Single-strand binding proteins do?

Answer 17

Bind to single strand DNA to prevent helix from reforming.

Question 18

What does the enzyme RNA primase do?

Answer 18

Synthesizes an RNA primer that attaches to 3’ end to begin DNA replication.

Question 19

What does the enzyme DNA polymerase I do?

Answer 19

Replaces RNA primer with DNA.

Question 20

What does the enzyme DNA polymerase II do?

Answer 20

The BUILDER. Replicates DNA strand by adding complementary nitrogenous bases to new daughter strand.

Question 21

What does the enzyme DNA ligase do?

Answer 21

Seals gaps between okasazki fragments into a single DNA molecule with phosphodiester bonds.

Question 22

What is DNAs monomer?

Answer 22

nucleotides

Question 23

What are nucleotides made out of?

Answer 23

Sugar molecule, phosphate group, and a nitrogenous base.

Question 24

What is a mismatched repair?

Answer 24

Incorrectly added base is detected after replication. Proteins detect and remove base from new strand by nuclease action.

Question 25

What is nucleotide excision repair?

Answer 25

When the damaged bases are repaired.