Nucleic acid

Question 1

What is the structure of a nucleotide

Answer 1

A circular phosphate, connected at an angle to a 5 sideded pentose sugar, which is connected at the other end to a recutangular nitrogen containing base.

Question 2

Name all of the pyramidines and their structures

Answer 2

Uracil, Cytosine, Thymine

Single ring structure of one hexagon only.

Question 3

Name all of the purines and their structures

Answer 3

Adenine and Guanine

Double ring structure with one hexagon connected to one pentagon

Question 4

What are the functions of nucleic acid?

Answer 4

1. Pass on genetic information by replication
2. Code for protein synthesis through specific base sequences

Question 5

How is DNA adapted to its function?

Answer 5

1. Very stable - can be passed through many generations without change
2. Large molecule - can carry lots of information
3. Helical cylinder - protects molecule from outside chemical and physical forces which may change it

Question 6

Describe Hershey-Chase experiment

Answer 6

1. A bacteriophage virus was used and radiocative isotopes of Sulfur in protein coat were tagged.
2. Virus invaded bacteria and inserted DNA into it
3. Mixture of bacteria and virus was blended and then spun in a cetrafuge to separate bacteria and protein coat
4. Pellet was discoloured but supernatant was glowing and radioactive.

Experiment was repeated but with radioactive isotopes of Phosphorus present in DNA and pellet was glowing instead.

Question 7

What did Hershey-Chase experiment prove?

Answer 7

DNA is the hereditary material that is passed on.

Question 8

How many bonds form between A-T and C-G?

Answer 8

A-T = 2 bonds
C-G = 3 bonds

Question 9

How does a sugar phosphate backbone form?

Answer 9

• Condensation reaction between nucleotides
• H2O forms as a biproduct
• Covalent bonds form between phosphate and
  pentose sugar

Question 10

What did Erwin Chargaff discover and how?

Answer 10

1) Organisms have different compositions of DNA and relative amounts of bases
2) In any DNA, number of A is same as T and G is same as C - shows the pairings

He found these out by looking at relative abundance of each base in lots of organisms.

Question 11

What did Franklin and Wilkins X-Ray Crystallography experiment reveal?

Answer 11

• DNA exists as a double stranded helix
• Twists every 34 angstrom
• 10 bases per twist
• Phosphorus is on the outside

Question 12

Who created the basic molecular model of DNA?

Answer 12

Watson and Crick

Question 13

DNA vs RNA

Answer 13

• DNA is longer
• DNA is double stranded, RNA is single
• DNA has 2 s-p backbones, RNA has one
• RNA has an -OH group connected to second
  carbon in pentose, DNA has only -H

Question 14

What relative direction do strands of DNA run in?

Answer 14

Antiparallel