Week 2

Question 1

DNA is made up of what two macromolecules?

Answer 1

Protein and Nucleic acids

Question 2

What are the two types of nucleic acids?

Answer 2

DNA and RNA

Question 3

What is a Nucleic acid?

Answer 3

Macromolecules composed of repeating subunits called nucleotides

Question 4

What makes up a nucleotide?

Answer 4

(1) a phosphate group,
(2) a five-carbon sugar, or pentose
(3) a cyclic nitrogen-containing compound called a base

Question 5

What sugar is used in DNA

Answer 5

In DNA, the sugar is 2-deoxyribose

Question 6

What is the sugar in RNA?

Answer 6

In RNA, the sugar is ribose

Question 7

What are the 4 common bases found in DNA?

Answer 7

-Adenine
-Guanine
-Cytosine
-Thymine

Question 8

What two bases are considered purines?

Answer 8

Adenine and guanine are double-ring bases called purines;

Question 9

What are the 4 bases found in RNA

Answer 9

-Adenine
-Guanine
-Cytosine
-Uracil

Question 10

What three bases are considered pyrimidines?

Answer 10

-cytosine, thymine, and uracil are single-ring bases called pyrimidines

Question 11

What bonds link together nucleotides?

Answer 11

Covalent phosphodiester bonds

Question 12

What bonds hold together the two polynecleotide chains of the double helix DNA?

Answer 12

Hydrogen Bonding

Question 13

How many hydrogen bonds are formed between Adenine and Thymine?

Answer 13

two hydrogen bonds

Question 14

How many hydrogen bonds are formed between Guanine and Cytosine?

Answer 14

three hydrogen bonds

Question 15

How are the sugar-phosphate backbones of two complementary strands oriented?

Answer 15

antiparallel; parallel but moving or oriented in opposite directions

Question 16

What is B-DNA and when does this state occur?

Answer 16

-In aqueous solutions
-low salt levels

The vast majority of the DNA molecules present in the aqueous protoplasms of living cells exist in the B conformation (10 nucleotides per turn)

Question 17

What is A-DNA and when does it take this formation?

Answer 17

-In high concentrations of salts
-or in a partially dehydrated state

A-DNA is shorter and thicker double helix

A right handed helix like B-DNA, but with 11 nucleotide pairs per turn

Question 18

What is Z-DNA and when does it take on this state?

Answer 18

A left-handed, doublehelical form

(Z for the zigzagged path of the sugar-phosphate backbones of the structure)

Z-DNA occurs in double helices that are G:C-rich and that contain alternating purine and
pyrimidine residues.

Has 12 base pairs per turn; a single deep groove; and much thinner than others

Question 19

How is DNA organized in all living cells?

Answer 19

It is supercoiled

Question 20

How are supercoils in DNA formed?

Answer 20

When one or both strands are cleaved

When the complementary strands
at one end are rotated or twisted around each other with the other end held fixed in
space—and thus not allowed to spin

Question 21

How are most DNA molecules supercoiled in vivo?

Answer 21

negative supercoiling in vivo

Question 22

At what point can biological functions of chromosomes can be carried out?

Answer 22

only when the participating DNA molecules are negatively supercoiled