DNA, RNA and Protein Synthesis

Question 1

What is the function of deoxyribonucleic acid?

Answer 1

Store genetic information.

Question 2

What is the function of ribonucleic acid?

Answer 2

Transfer genetic information from the DNA to the ribosomes.

Question 3

Structure and function of a nucleotide.

Answer 3

Pentose sugar, nitrogen base and a phosphate group. They are the monomers of DNA and RNA.

Question 4

What is the pentose sugar in DNA and the pentose sugar in RNA?

Answer 4

DNA - deoxyribose

RNA - ribose

Question 5

What base replaces thymine in RNA?

Answer 5

Uracil.

Question 6

How is the sugar-phosphate backbone formed?

Answer 6

Nucleotides join via condensation reaction between phosphate groups of one nucleotide and the sugar of another forming a phosphodiester bond, creating a polynucleotide.

Question 7

What holds the two polynucleotide strands together?

Answer 7

Hydrogen bonds between complementary base pairings.

Question 8

How many bonds form between the bases?

Answer 8

Two between A and T, three between G and C.

Question 9

Describe the structure of DNA.

Answer 9

To antiparallel polynucleotides, twisted to form a double helix.

Question 10

Structure of RNA.

Answer 10

Short, single polynucleotide strand.

Question 11

Why does DNA replication occur?

Answer 11

So that daughter cells have the full amount of DNA.

Question 12

What is semi conservative replication?

Answer 12

Replication where half of the strands in the new DNA molecule are from the original molecule - genetic continuity.

Question 13

What does DNA helicase do in DNA replication?

Answer 13

Breaks hydrogen bonds between the bases on the two polynucleotide strands allowing the helix to unwind.

Question 14

What happens in DNA replication after the helix unwinds?

Answer 14

The original strands act as template for free nucleotides that are attracted to their exposed complementary bases.

Question 15

What does DNA polymerase do in DNA replication?

Answer 15

Catalyses the condensation reaction that join the free nucleotides to the original strand using hydrogen bonds.

Question 16

Active site of DNA polymerase is coulee tart to the 3’ end of the new DNA strand and so can only add nucleotides to this new, what does this mean for the new strand?

Answer 16

The new strand is created in a 5’ to 3’ direction and the DNA polymerase moves down it in a 3’ to 5’ direction.

Question 17

What did Meselson and Stahl show?

Answer 17

DNA is replicated semi-conservatively.

Question 18

Describe Meselson and Stahl’s experiment.

Answer 18

1. Two samples of bacteria grown, one in light nitrogen containing broth, one in heavy nitrogen containing broth
2. Sample of DNA taken from each and spun in a centrifuge, pellet of heavy settled lower down than the pellet of light
3. Bacteria grown in heavy nitrogen broth was then put in light nitrogen broth and left for one round of replication, a DNA sample was taken and spun in the centrifuge
4. DNA settled in the middle showing that the DNA was a combination of heavy and light nitrogen - semi conservative
   4.