Unit 1: Nucleic acids

Question 1

What is a nucleic acid ?

Answer 1

A long repeating chain of nucleotides

Question 2

Give 2 examples of nucleic acids

Answer 2

• DNA
• RNA

Question 3

What are the 3 components of a nucleotide ?

Answer 3

• 3 phosphate groups
• A central sugar ring
• A nitrogenous base

Question 4

What is a nucleoside ?

Answer 4

Contains a sugar and a base without the phosphate groups

Question 5

What is the sugar in DNA ?

Answer 5

Deoxy-ribose

Question 6

What direction are the carbon atoms always numbered in ?

Answer 6

Clockwise

Question 7

What are the 4 bases in DNA ?

Answer 7

• Cytosine
• Thymine
• Adenine
• Guanine

Question 8

What are the 2 categories of nucleotide bases ?

Answer 8

• Pyrimidines
• Purines

Question 9

Which 2 bases are in the pyrimidines ?

Answer 9

• Cytosine
• Thymine

Question 10

Which 2 bases are in the purines ?

Answer 10

• Adenine
• Guanine

Question 11

What is a good way of remembering which bases fit into which category ?

Answer 11

• Smaller 2 bases (C and T) are in the longest word (Pyrimidines)
• Larger 2 bases (A and G) are in the shortest word (Purines)

Question 12

What is a dNTP ?

Answer 12

A deoxyribose + adenine + triphosphate

Question 13

What is the nucleotide for adenine ?

Answer 13

Deoxy-adenosine triphosphate

Question 14

What is the nucleotide for guanine ?

Answer 14

Deoxy-guanosine triphosphate

Question 15

What is the nucleotide for cytosine ?

Answer 15

Deoxy-cytidine triphosphate

Question 16

What is the nucleotide for thymine ?

Answer 16

Deoxy-thymidine triphosphate

Question 17

What is directionality in reference to DNA ?

Answer 17

That DNA is read in the 5’ to 3’ direction (From left to right)

Question 18

Where are new nucleotides added to a strand of DNA ?

Answer 18

At the 3’ end

Question 19

What is chargaffs rule ?

Answer 19

That in double stranded DNA, there is a 1:1 ratio of purine molecules to pyrimidine molecules

Question 20

Why is bonding between G and C stronger than between A and T ?

Answer 20

• Between C and G is 3 H bonds
• Between A and T is 2 H bonds
• Between G and C there is a higher affinity, they are more stable and therefore harder to separate

Question 21

What protein structure is a DNA helix an example of ?

Answer 21

A secondary structure

Question 22

What are the 3 key differences between DNA and RNA ?

Answer 22

1) RNA is single stranded
2) RNA contains ribose as opposed to deoxyribose
3) RNA contains uracil in place of Thymine

Question 23

Why is ribose very reactive and less stable than deoxyribose ?

Answer 23

As ribose has an extra O on its C2’

Question 24

What is the job of mRNA?

Answer 24

Codes for cellular proteins

Question 25

What is the job of tRNA ?

Answer 25

Involved in bringing amino acids to the ribosome

Question 26

What is the job of rRNA?

Answer 26

Structural RNAs that contribute to the ribosome

Question 27

What is the job of snRNA?

Answer 27

Involved in the mRNA splicing in the nucleus

Question 28

How can RNA give rise to a secondary structure ?

Answer 28

As base paring can occur between nucleotides in a single RNA strand

Question 29

How can RNA give rise to a tertiary structure ?

Answer 29

Due to further 3 dimensional folding