Nucleic Acids

Question 1

Describe the structure of a nucleotide.

Answer 1

Phosphate 
           ⬇️
            O
              \／＼\_\_\_BASE
               |\_\_\_|
                 ⬆️
               Deoxyribose

Question 2

What does DNA polymerase do?

Answer 2

•causes a condensation reaction between the new nucleotide to the original strand

Question 3

What does DNA helicase do?

Answer 3

“Un-zips” the DNA by breaking the H bonds between the bases and separated the 2 strands of DNA

Question 4

Why does DNA polymerase only work in a 5’ to 3’ direction?

Answer 4

• anti parallel strands

* shape is different when the enzyme moves in a different direction (therefore won’t fit in the active site)

Question 5

Out of the labelled parts of the nucleotide, which molecule;
A) is not a base and is different in an RNA molecule
B) contains nitrogen

          ©️                  
            O               🅰️
              \／＼\_\_\_BASE 
               |\_\_\_|
                🅱️

Answer 5

A) B - ribose in RNA not deoxyribose

B) A - bases only contain N

Question 6

The sequence of bases on one strand of DNA is important for protein synthesis. What is it’s role?

Answer 6

To maintain the cells sequence of amino acids that code for the cells genetic info

Question 7

How are the two strands of the DNA molecule held together?

Answer 7

H bonds between the pairs

Question 8

Give one advantage of DNA molecules having 2 strands

Answer 8

Identical strands of DNA can be made by DNA replication

Question 9

Tubes of DNA used in replication;
A:             B:             C:
|\_\_|⬅️       |   |           |   |
|   |            |   |           |\_\_|⬅️
|   |            |\_\_|⬅️      |   |
|\_\_|            |\_\_|           |\_\_|
 N14          N15         N14 and N15
1. What do tubes A and B show about density of the DNA formed using the 2 different forms of N?
2. Explain the position of the band in tube C

Answer 9

1. A is light N (not as dense)
   B is heavy N (very dense)
2. Hybrid molecule containing heavy and light strands. The new strand is made of N14