Dna Structure

Question 1

What is a nucleotide

Answer 1

A repeating unit that makes up DNA made of nitrogenous base, sugar, phosphate

Question 2

What are purines

Answer 2

The two purines are Adenine and Guanine

Question 3

What are Pyrimidines

Answer 3

The two pyrimidines are Thymine and Cytosine

Question 4

Difference between RNA bases and DNA bases

Answer 4

Instead of Thymine Rna contains Uracil

Question 5

What type of sugar is in the bases

Answer 5

2’- deoxyribose in cyclic hemiacetal form

Question 6

How are bases connected

Answer 6

They are connected via phosphordiester bonds, created by removing oxygen from the phosphate and replacing it with the oxygen from the ribose, releasing h2o

Question 7

Deoxiribonucleoside nomenclature

Answer 7

Base + 2’ deoxyribose

Eg: deoxyadenosine, deoxyguanosine, deoxycitidine, deoxythimidine

Question 8

deoxyribonucleotide nomenclature

Answer 8

base + 2 ‘deoxyribose + 1 phosphate

Eg: deoxyadenosine monophosphate (dAMP)

Question 9

deoxyribonucleoside diphosphate nomenclature

Answer 9

Base + 2’ deoxyribose + 2 phosphate

Eg deoxyadenosine diphosphate (dADP)

Question 10

Deoxyribonucleoside triphosphate nomenclature

Answer 10

Base + 2’ deoxyribose + 3 phosphate
Eg deoxyadenosine triphosphate (dATP)

Question 11

Chargaffs rules

Answer 11

1. Bases are not equally represented
2. Dna from an organism or same species have the same base composition in every cell
3. Dna in different species can vary
4. A=T, C=G

Question 12

(A+G)/(T+C) =

Answer 12

= 1

Question 13

watson crick model

Answer 13

1. Consists of antiparallel strands,
2. Bases are inside the helix
3. Held together through hydrogen bonds
4. Strict pairing between the bases
5. Complementary strands
6. Right-handed double helix
7. Minor and major grooves
8. Hydrophobic interactions between horizontally stacked basepairs stabilise the dna making it rigid

Question 14

B from dna

Answer 14

Watson and crick model

Question 15

How many base pairs in 1 b form turn

Answer 15

10 base pairs = 3.4 nm

Question 16

What are the measurements of dna

Answer 16

Width = 2nm
Height between bases = 0.34nm
Height between one turn = 3.4nm

Question 17

Methylation of bases

Answer 17

Most commonly in cytosin in eukaryotes
CH3 binds to another molecule physically and chemically altering its properties
Typically acts to repress gene transcription

Question 18

How does dna fit into cells

Answer 18

Dna is supercoiled and packaged with proteins, making chromatin

Question 19

Supercoiling

Answer 19

Turns are added or removed
Positive supercoiling = coiling in the Sam direction as the helix
Negative supercoiling = helix twists in on itself in the other direction

Question 20

Packaging of dna

Answer 20

Dna is wrapped around histones to take up less space and then is further coiled until it’s tightly packed and present as chromatin