Dna

Question 1

Describe the structure of DNA (5)

Answer 1

-polymer of nucleotides
-each nucleotide formed from deoxyribose, phosphate, organic base
-phosphodiester bond b/t adjacent nucleotides
-double helix
-H bonds b/t comp base pairs

Question 2

Describe how a Phosphodiester bond is formed between two nucleotides within a DNA molecule (3)

Answer 2

-condensation reaction
-b/t phosphate and deoxyribose
-via DNA polymerase

Question 3

Describe how the separation of strands occurs (3)

Answer 3

-DNA helicase
-breaks weak H bonds b/t comp base pairs
-template strands

Question 4

Describe the role of DNA polymerase in the semiconservative replication of DNA. (3)

Answer 4

-Joins free adjacent nucleotides
-forms phosphodiester bonds
-condensation reaction

Question 5

In semiconservative replication of DNA, what is the role of the single-stranded DNA fragments? (2)

Answer 5

-acts as template
-determines order of bases

Question 6

In semiconservative replication of DNA, what is the role of the DNA nucleotides? (1)

Answer 6

-forms complimentary base pairs

Question 7

Give three features of DNA and explain how each is important to semiconservative replication of DNA. (3)

Answer 7

-weak H bonds b/t comp bases allows separate strands
-double stranded so both acts as template strands
-comp base pairs allows accurate replication

Question 8

Use your knowledge of enzyme action to explain why DNA polymerase is used in opposite directions on DNA strands. (4)

Answer 8

-DNA has antiparallel strands
-shape of nucleotides are different
-enzymes have active site w/ specific shape
-only 3’ carbon can bind w/ active site of DNA polymerase

Question 9

Why is it that humans and grasshoppers have similar percentages of bases but they’re very different organisms? (3)

Answer 9

-have different genes
-so different base sequences
-so different amino acid sequences are coded