M2.2. DNA Double Helix

Question 1

involves two polynucleotide chains coiled (around a CENTRAL AXIS in the form of RIGHT-HANDED DOUBLE HELIX) around each other in a helical fashion

Answer 1

SECONDARY STRUCTURE of a DNA.

Question 2

The ____ run anti-parallel (opposite directions) to each other, i.e., 5’ - 3’ and 3’ - 5’

5’: phosphate
3’: hydroxyl

Answer 2

polynucleotides

Question 3

The nitrogenous bases (in the DNA) are located at the ____ and are held together by a ____.

Answer 3

1. center
2. hydrogen bonds

Question 4

Complementary partners of these Nitrogenous bases:
1. %A = ____.
2. %C = ____.

Answer 4

1. %T
2. %G

Question 5

the DNA sequence of bases on one polynucleotide is ____ to the other polynucleotide.

Answer 5

complementary

Question 6

are pairs of bases in a nucleic acid structure that can hydrogen-bond to each other

Answer 6

Complementary Bases

Question 7

are strands of DNA in a double helix with base pairing such that each base is located opposite its complementary base.

Answer 7

Complementary DNA strands

Question 8

DNA molecules produce exact duplicates of themselves

Answer 8

Replication

Question 9

Old strands act as templates for the synthesis of ____.

Answer 9

new strands

Question 10

• checks the correct base pairing
• catalyzes the formation of phosphodiester linkages

Answer 10

DNA polymerase

Question 11

• has one new DNA strand and old DNA strand
• they are semi-consevative.

Answer 11

newly synthesized DNA

Question 12

DNA polymerase enzyme can only function in the ____ direction

Answer 12

5’-to-3’

Question 13

• grows continuously in the direction of unwinding
• top

Answer 13

leading strand

Question 14

grows in segments in the opposite direction

• what are these segments called?
• connected by DNA LIGASE

Answer 14

lagging strand

Okazaki fragments

Question 15

1. origin of DNA replication?
2. is bidirectional from these sites (replication forks)
3. Multiple-site replication enables rapid ____.

Answer 15

1. within a MOLECULE.
2. DNA replication.
3. DNA synthesis.

DNA replication usually occurs at multiple sites within a molecule.

Question 16

Upon DNA replication the large DNA molecules INTERACTS with ____ to fold long DNA molecules.

Answer 16

histone proteins

Question 17

The histone–DNA complexes are called

Answer 17

CHROMOSOMES

Question 18

CHROMOSOME is:
1. ____ by mass DNA
2. ____ by mass protein

Answer 18

1. 15%
2. 85%

Question 19

Cells of different kinds of organisms have ____ numbers of chromosomes.

Answer 19

different

EX. Number of chromosomes in a human cell 46, a mosquito 6, a frog 26, a dog 78, and a turkey 82

Question 20

Chromosomes occur in?

a. matched (homologous) pairs.
b. different (heterologous) pairs.

Answer 20

a. matched (homologous) pairs.

EX. The 46 chromosomes of a human cell constitute 23 homologous pairs