DNA and DNA Replication

Question 1

Define DNA/RNA

Answer 1

Polynucleotides composed of mono nucleotides linked by condensation reaction

Question 2

Name the main enzyme in DNA replication

Answer 2

DNA polymerase

Question 3

Describe the structure of a nucleotide

Answer 3

Pentose sugar, nitrogenous base and a phosphate group

Question 4

How do two nucleotides form

Answer 4

Condensation reaction to form a phosphodiester bond

Question 5

Describe the 3 features of the genetic code

Answer 5

Universal = same four bases used in the DNA of every organism

Non-overlapping = no overlap between triplet codes

Degenerate = some amino acids are coded for by more than one codon (20 amino acids but 64 possible combinations)

Question 6

Describe the structure of a DNA molecule

Answer 6

Double helix with two polynucleotide chains consisting of a sugar phosphate backbone held together by hydrogen bonds between the complementary bases

Question 7

How many H bonds between thymine/adenine and guanine/cytosine?

Answer 7

Two between T/A

Three between G/C

Question 8

In which part of the cell cycle does DNA replicate?

Answer 8

S phase

Question 9

What do the original strands act as in DNA replication?

Answer 9

Each of the two original strands act as a template for the new strands

Question 10

Why is DNA replication describe as semi-conservative?

Answer 10

After replication the DNA is made up of one original strand (thus strand is ‘conserved’ and one new strand

Question 11

Describe the stages of DNA replication

Answer 11

1) DNA helicase binds to DNA and breaks the hydrogen bonds between the two strands causing the helix to unwind and the strands to separate
2) Free-floating nucleotides form hydrogen bonds with complementary bases
3) DNA polymerase forms phosphodiester bonds between the original and new strand

Question 12

What is the orientation of DNA strands

Answer 12

They run anti-parallel