Exam 4 - Quiz 1

Question 1

In nucleic acids, the difference between deoxyribose and ribose lies at which carbon?

Answer 1

2’

Question 2

In nucliec acids, the nitrogenous base is attached to the ____ carbon of the sugar

Answer 2

1’

Question 3

Which of the following bases has a single heterocyclic ring structure?
Cytosine
Adenine
Thymine
Two of the above
None of the above

Answer 3

Two of the above

Cytosine and Thymine

Question 4

The DNA double helix resembles the structure of a spiral staircase. Which DNA component is analogous to the spiral staircase’s banister (side rails)?

Answer 4

The sugar-phosphate backbone

Question 5

The form of DNA found in living cells is

Answer 5

B-DNA

Question 6

The percentage of cytosine in a bacterial genome was determined to be 20%. What is the percent of Adenine?

Answer 6

30 %

A%= T% C% = G%
A% + T% + C% + G% = 100%

C% = 20%
G% = 20 %
A% + T% = 60% 60%/2 = 30%

Question 7

The 5’ end of nucliec acid molecule refers to the _______ group on the 5’ carbon of the first nucleotide.

Answer 7

Phosphate

Question 8

How many hydrogen bonds would connect the DNA sequences CATG and its complement on the other strand in a double helix?

Answer 8

10
C => 3 bonds
A => 2 bonds
T => 2 bonds
G => 3 bonds
Total 10 bonds

Question 9

Which of the following  bases has a double heterocyclic ring structure?
Cytosine
Guanine
Thymine
Uracil
None of the above

Answer 9

Guanine

Guanine and Adenine have double heterocyclic ring structures

Question 10

For double-stranded DNA which of the following base ratios ALWAYS equal 1?
A/G
C/T
C/G
Two of the above
All of the above

Answer 10

C/G

Chargaff’s Rule

A = T ; C = G

Question 11

Deoxyribonucleotides lack a \_\_\_\_\_\_
Nitrogenous base
5' Phosphate
3' hydroxyl group
2' hydroxyl group
Pentose sugar

Answer 11

2’ hydroxyl group

Question 12

Ribonucleosides lack a \_\_\_\_\_\_
Nitrogenous base
5' phosphate group
3' Phosphate group
2' hydroxyl group
Pentose Sugar

Answer 12

5’ phosphate group

Ribonucleosides lack 5’ phosphate group

Question 13

Which of the following is NOT a difference between RNA and DNA?

• RNA is generally shorter than DNA
• RNA is usually single-stranded whereas DNA is double-stranded
• RNA contains ribose whereas DNA contains deoxyribose
• RNA contains uracil whereas DNA contains thymine
• All of the above are differences

Answer 13

All of the above are differences

Question 14

The double-stranded DNA molecule of the newly discovered Elradicus libanii was found by electron microscopy to have a length of 17 micrometers. How many base pairs are present in this molecule?

Answer 14

50,000

1 micro meter = 1000 nanometer (nm)

10 base pairs (BP) in one complete turn
One turn = 3.4 nm
(17,000 nm / 3.4 nm) = 5000 turns
5000 turns * 10 BP = 50,000

Question 15

The double-stranded DNA molecule of the newly discovered Elradicus libanii was found by electron microscopy to have a length of 17 micrometers. How many complete turns of the helix are present in this molecule?

Answer 15

5,000 turns

1 micro meter = 1000 nanometer (nm)

10 base pairs (BP) in one complete turn
One turn = 3.4 nm
(17,000 nm / 3.4 nm) = 5000 turns

Question 16

A nucleic acid molecule that has 20% A, 30% C, 20% G and 30% T is most likely?

single-stranded DNA single-stranded RNA double-stranded DNA double-stranded RNA

Answer 16

Single- stranded DNA

Chargaff’s rule
In double-stranded, DNA

A = T; G = C
A and T are not equal, therefore it’s a single stranded DNA

Question 17

A large nucleic acid molecule that has 20% A, 30% C, 30% G and 20% U is most likely?

single-stranded DNA single-stranded RNA double-stranded DNA double-stranded RNA

Answer 17

Double stranded RNA

T is replaced with U, therefore it’s RNA

Chargaff’s rule is full-filled. It’s double stranded

Question 18

A double-stranded DNA molecule is 5,000 base-pairs long. How many complete turns are present in this molecule?

Answer 18

500
10 base pairs per turn
5000/10 = 500

Question 19

A double-stranded DNA molecule is 5,000 base-pairs long. How long is this molecule?
170 nm 
  500 A 
  1.7 micrometers
  0.17 micrometers
  none of these choices

Answer 19

1.7 micrometers

5,000 / 10 = 500 turns

500 turns * 3.4 nm = 1700 nm
1700 nm/ 1000 = 1.7 micrometers

Question 20

When DNA is \_\_\_\_\_\_, hydrogen bonds are broken.
renatured 
denatured 
saturated 
polymerized

Answer 20

Denatured

Question 21

For double-stranded DNA which of the following base ratios ALWAYS equals 1?
  (A+T)/(C+G) 
  (A+G)/(C+T) 
  (G+T)/(A+C) 
  two of the above 
  all of the above

Answer 21

Two of the above
(A+G)/(C+T)
(G+T)/(A+C)

Chargaff

1. A + G = T + C
2. A = T ; C = G
3. A + T almost never equals to C + G

Question 22

Which of the following DNA molecules is the most thermodynamically stable?
5’GGGGAAAACCCCTTTT 3’
3’CCCCTTTTGGGGAAAA 5’

5’AGCGCGCAGCGTTTTT 3’
3’TCGCGCGTCGCAAAAA 5’

5’AAAGGAATTCCGTTAA 3’
3’TTTCCTTAAGGCAATT 5’

5’AAAAAAGGGGGGTTTT 3’
3’TTTTTTCCCCCCAAAA 5’

5’GCATCGAGGCCGGCTG 3’
3’CGTAGCTCCGGCCGAC 5’

Answer 22

5’GCATCGAGGCCGGCTG 3’

3’CGTAGCTCCGGCCGAC 5’