3.1.5 Nucleic Acids

Question 1

Describe how a phosphodiester bond is formed between two nucleotides within a DNA molecule

Answer 1

+ condensation reaction
between phosphate an
deoxyribose
+ catalysed by DNA polymerase

Question 2

Describe how the separation of strands occurs

Answer 2

+ DNA helicase breaks hydrogen
bonds between base pairs/
polynucleotide chains

Question 3

Describe the role of DNA polymerase in the semi-conservative replication of DNA

Answer 3

+ joins adjacent DNA nucleotides
+ catalyses condensation
reactions
+ catalyses formation of phosphodiester

Question 4

What is the role of the single-stranded DNA fragments

Answer 4

+ template
+ determines the order nucleotides/bases

Question 5

What is the role of DNA nucleotides

Answer 5

+ forms complementary pairs

Question 6

Contrast the structures of ATP and a nucleotide found in DNA

Answer 6

1. ATP has ribose and DNA nucleotide has deoxyribose
2. ATP has 3 phosphate groups and DNA nucleotide has 1 phosphate group
3. ATP - base always adenine and in DNA nucleotide base can vary

Question 7

Explain why the enzymes work in opposite directions

Answer 7

+ DNA has anti parallel strands
+ Shape of the nucleotides is different/aligned differently
+ Enzymes have active sites with specific shape
+ Only binds to substrates with complementary shape

Question 8

Explain why nucleotides can only be added in a 5’ to 3’ direction

Answer 8

+ DNA polymerase joins nucleotides
+ It is specific
+ Only complementary with 5’ end of strand
+ Strands of 5’ end and 3’ end are different