2.1.3 Nucleotides and Nucleic acids

Question 1

What are the components of a nucleotide

Answer 1

pentose sugar
nitrogenous base
phosphate group

Question 2

Differences between DNA and RNA

Answer 2

DNA - deoxyribose sugar
RNA - ribose sugar

DNA -> ATCG
RNA -> AUCG

Question 3

Which bases are purines

Answer 3

adenine
guanine

Question 4

Which bases are pyrimidines

Answer 4

cytosine
thymine
uracil

Question 5

Describe how nucleotides are joined

Answer 5

joined through a condensation reaction between the phosphate group of one nucleotide and the pentose sugar of another nucleotide
- forms a phosphodiester bond

Question 5

What is the difference in structure between purines and pyrimidines

Answer 5

purines have a double ring structure whereas pyrimidines have a single ring structure

Question 6

What is the structure of DNA

Answer 6

two strands of antiparallel DNA in a double helix shape

Question 7

How many hydrogen bonds form between adenine and thymine

Answer 7

two hydrogen bonds

Question 8

How many hydrogen bonds form between adenine and thymine

Answer 8

three hydrogen bonds

Question 9

Describe the process of semi-conservative replication

Answer 9

• DNA helicase breaks the hydrogen bonds between base pairs to expose a single strand of DNA
• free nucleotides attach to exposed bases
• adjacent nucleotides are joined together by DNA polymerase

Question 10

Describe the role of DNA polymerase

Answer 10

catalyses the condensation reaction between the pentose sugar and phosphate groups