B.8. Nucleic Acids

Question 1

The structure of Adenine and Guanine

Answer 1

Double ring structure consisting of a 6-sided ring attached to a 5-sided ring = PURINES

Question 2

The structure of Cytosine, Thymine and Uracil

Answer 2

Single 6-sided ring = PYRIMIDINES

Question 3

Which part of a DNA or RNA is charged?

Answer 3

Phosphate group

→ Partially responsible for water solubility of nucleic acids

Question 4

Nucleotides polymerise to form what?

Answer 4

Nucleic acids (Polynucleotides)

Question 5

What do Nucleic acids consist of?

Answer 5

+ chains of nucleotides formed by enzyme catalysed condensation reactions

Question 6

Which C is the base covalently bonded to?

Answer 6

C1

Question 7

Which carbon is the phosphate group attach to? And how does it attach?

Answer 7

C5 → phosphate group condenses w/ the -OH group of the sugar

Question 8

How is the sugar-phosphate backbone formed in DNA and RNA?

Answer 8

The phosphate of one nucleotide combines w/ the hydroxyl group on the C3 of the sugar on another nucleotide = releasing water = forming covalent bond

Question 9

How do the 2 strands of DNA bond together?

Answer 9

By H.bonding betw/ the complimentary base pairs located betw/ the 2 backbones of sugar and phosphate groups.

Question 10

How many H.bonds do A and T form?

Answer 10

2 → form complimentary base pairings

Question 11

How many H.bonds do C and G form?

Answer 11

3 → form complimentary base pairings

Question 12

What is part of the reason for the AT and CG bases to only be able to pair together?

Answer 12

Only the molecular geometry of the single ringed and double ringed complimentary base pairs give a similar dist. betw/ the 2 backbones of DNA

Question 13

What other forces stabilise the backbone of the double helix?

Answer 13

+ van der Waal’s force between base pairs

+ Dipole-Dipole forces between base pairs

Question 14

Why is there twisting betw/ the sugar-phospate backbone of DNA?

Answer 14

To minimise the electrostatic repulsions betw/ negatively charged phosphate residues.

Question 15

How many nucleotide completes a turn of a helix?

Answer 15

10

Question 16

What allows DNA to replicate itself exactly?

Answer 16

The complementary base pairings

Question 17

What is the role of DNA?

Answer 17

To reproduce itself and carry information which encodes the proteins in an organism.

Question 18

What is a gene?

Answer 18

A section of DNA that codes for a protein.

Question 19

What is the origin of the negative charge of the DNA?

Answer 19

The phosphate (ion) group

Question 20

What is the strength of Phosphoric acid?

Answer 20

Weak = ionizes in water to reach acid-base equilibrium at that temp.

Question 21

What do cells mostly contain?

Answer 21

Water

Question 22

At the pH of cells what does the phosphate group in the nucleotide contain?

Answer 22

Negatively charged Oxygen atoms

Question 23

What charge do histone proteins have?

Answer 23

Positive +

Question 24

What makes it possible to remove or insert parts of DNA at diff places in or betw/ cells?

Answer 24

Restriction Enzymes
(Restriction Endonucleases)

Question 25

Benefits of GM foods (9)

Answer 25

1) Resistance to Herbicides = reduces use 2) Resistance to Pesticides = Don't kill useful insects 3) Resistance to Diseases 4) Decreasing risk of food allergies = e.g. soybeans 5) Increase Yield 6) Resistance to harsh climates = Withstand cold/ salt 7) Nutrient enriched = Golden rice = for ppl lacking 8) Economics 9) Environmental = Less damage to water supply from herbicides and pesticides

Question 26

Concerns of GM foods (6)

Answer 26

1) Impact on other organisms 2) Resistance to pesticides 3) Allergies 4) Gene-flow to other species = resistant weed 5) Labelling of GM foods = in some countries required but some not = should label to give consumer choice 6) Health effects