DNA is a polymer of nucleotides

Question 1

What did Leven determine about DNA? When?

Answer 1

1909-1929: DNA contains equal proportions deoxyribose, nitrogenous bases and phosphates.

Question 2

What did Chargaff determine about DNA? When?

Answer 2

1950s: # of A = # of T; # of G = # of C

Question 3

What did Franklin and Wilkins determine about DNA? When?

Answer 3

Early 1950s: x-ray diffraction shows DNA is a double helix

Question 4

What did Watson and Crick determine about DNA? When?

Answer 4

1953: Deduced the double helical structure of DNA.

Question 5

When forming a DNA strand, what carbon of deoxyribose do new bases attach to? How?

Answer 5

New bases attach to the 3’ carbon via single phosphate group.

Question 6

How does polymerization occur?

Answer 6

Via formation of 3’ to 5’ phosphodiester bonds.

Question 7

What type of reaction occurs for the polymerization of DNA?

Answer 7

Enzyme-catalyzed condensation reaction.

Question 8

What is released as a result of the polymerization of DNA?

Answer 8

Pyrophosphate and water

Question 9

What does the 5’ end of DNA always have?

Answer 9

3 phosphates attached

Question 10

How do nitrogenous bases form pairs?

Answer 10

Hydrogen bonding

Question 11

List the nitrogenous base pairs.

Answer 11

AT (or AU)
GC

Question 12

How many hydrogen bonds form between adenine and thymine?

Answer 12

2

Question 13

How many hydrogen bonds form between guanine and cytosine?

Answer 13

3

Question 14

In which direction are the two strands of DNA oriented against each other?

Answer 14

5’ to 3’

Question 15

What is the distance between the two C1’ carbons in a base pair?

Answer 15

10.85 A

Question 16

Why do purines always bond with pyrimidines?

Answer 16

Only they fit the 10.85 A distance without distorting the double helix backbone while maintaining H-bond distance

Question 17

Which pair is stronger CG or AT?

Answer 17

CG

Question 18

What is the implication of base pairing for DNA replication?

Answer 18

Can easily copy DNA using a single strand of parental DNA as a template.

Question 19

What are some common rules to follow when writing a DNA/RNA sequence?

Answer 19

Conventionally written from 5’ to 3’
Abbreviate the bases
Show only one strand