Components Of DNA

Question 1

Describe the shape of sugars in DNA- how many carbons

Answer 1

5 carbon sugars- form cyclic structure

Question 2

Which isomer of sugar exists in DNA?

Answer 2

B isomer rather than alpha
B isomer- OH on C1 is point up
Alpha isomer- Oh on C1 is pointing down

Question 3

What is the sugar in DNA and RNA and what is the difference?

Answer 3

DNA has deoxyribose and RNA has ribose

Ribose has OH at 2’ whereas deoxyribose has H

Question 4

What are the bases derivatives of and which are derivatives of what?

Answer 4

All of the bases are derivatives of pyrimidine or purine
Adenine and guanine are purines
Cytosine and thymine are pyrimidines

Question 5

Describe the structure of adenine

Answer 5

Derivative of purine
Has an amino group
No H on its nitrogen so it can accept H

Question 6

Describe the structure of guanine

Answer 6

Derivative of purine
Has a ketone group and amino group
Has a H on its nitrogen so it can donate H

Question 7

Describe the structure of cytosinen

Answer 7

Derivative of pyrimidine
Has an amino group and Ketone group
No H on its nitrogen- can accept H

Question 8

Describe the structure of thymine

Answer 8

Derivative of pyrimidine
Has two ketone groups
It has H on its nitrogen so it can donate H

Question 9

What is a nucleoside?

Answer 9

A base with an attached sugar

Question 10

Where are the sites of attachments on a nucleoside

Answer 10

Site of attachment is C1’ on sugar and N1 in the base by a glycosidic bond

Draw

Question 11

What is a nucleotide?

Answer 11

A nucleotide is a base attached to a sugar and a phosphate

Question 12

Describe the nature of phosphates

Answer 12

They have a negative charge

The more phosphates, the more charge, the more anionic the structure

Question 13

Describe the sites of attachment in a nucleotide

Answer 13

The 3’ or 5’ of name show which position the phosphate is attached to the sugar
The base is attached at C1 position on the sugar

Question 14

What is cAMP and describe its structure

Answer 14

Important signalling molecule for flight or fight response
Nucleotide
Consists of ribose sugar
Phospohodiester- phosphate is attached at 3’ and 5’ position

Question 15

What is a polynucleotide and describe nature and site of attachment

Answer 15

Polymer of nucleotides
Nucleotides are bonded together by phospohodiester bonds

Nucleotide is bonded at 3’ position to another nucleotide at 5’ position

Question 16

Why are polynucleotide polyanions and have a UV absorbance?

Answer 16

This is because each phospohodiester bond has a negative charge so it is a polyanion at pH7 and has a strong UV absorbance

Question 17

How do you measure DNA concentration?

Answer 17

Measure by UV absorbance at Ymax- 260nm

Question 18

Are bases planar and why?

Answer 18

Bases are planar because they are aromatic

Question 19

Describe the position of phosphate, sugar and base in DNA helix

Answer 19

Phosphate and sugar form the backbone of the polymer

The bases project outwards from sugar- side chain

Question 20

Which bond bonds bases to sugar ?

Answer 20

Joined through N- glycosidic bonds

Question 21

What is a phospohodiester bond?

Answer 21

Joins successive sugar molecules in a polynucleotide

Joined by the O on the phosphate group at 3’ of one sugar to 5’ of other sugar

Question 22

What is a glycosidic bond?

Answer 22

A bond that joins two sugars together by merging OHs on 2’ and 4’ position

Question 23

Describe the nature of the chain

Answer 23

It has polarity
One end has 5’ end OH free and other end has 3’ end OH free
5’ ->3’ phosphodiester bond