Nucleic Acids

Question 1

What elements are in nuclei acids?

Answer 1

CHONP
Carbon
Hydrogen
Oxygen 
Nitrogen 
Phosphurus

Question 2

What is the structure of DNA?

Answer 2

• Pentose sugar
• Phosphate group
• Nitrougenous base (T,A,G,C)

Question 3

What is DNA built up of ?

Answer 3

Made up of basic blocks called nucleotides

Question 4

What are the 4 nucleotides?

Answer 4

A, T, C, G

Question 5

What are 3 differences between RNA and DNA?

Answer 5

• The sugar (ribose) compared to dna (deoxyribose)
• Uracil instead of thymine
• RNA is usually single stranded

Question 6

Describe the semi-conservative replication of DNA

Answer 6

1. An enzyme, DNA helicase, causes the two strands of the DNA to separate.
2. DNA helicase, completes the separation of the strand.
3. Meanwhile, free nucleotides that have been attracted to their complimentary bases.
4. Once the activated nucleotides are lined up, they are joined together by DNA polymerase.
5. The remaining unpaired bases continue to attract their complimentary nucleotide.
6. All the nucleotides are joined to form a complete polynucleotide chain using DNA polymerase.
7. Two identical molecules - one original strand and one newly formed molecule - semi conservative replication.

Question 7

What happens if the sequence is copied incorrectly?

Answer 7

A mutation

Question 8

Describe transcription

Answer 8

1. mRNA made in the nucleus
2. Hydrogen bonds between bases break and DNA uncoils
3. A complimentary strand is made by copying the DNA strand, using it as a template.
4. mRNA then transports the complimentary strand to the ribosome through a nuclear pore.

Question 9

Describe Translation

Answer 9

1. During translation amino acids form together to form a polypeptide chain.
2. mRNA attaches to a ribosome and tranfer RNA (tRNA) collects amino acids from the cytoplasm
3. tRNA attaches to mRNA by complimentary base pairing
4. Amino acids attached to tRNA molecule join by a peptide bond and the tRNA then dettaches from the amino acids.
5. This process is repeated thus leading to the formation of a polypoptide chain, until a stop codon is reached on mRNA and the process of protein synthesis

Question 10

What is the role of rRNA?

Answer 10

Important in maintaining structural stability of the proteinsynthesis sequence and plays a biochemical role in catalysing the reaction.

Question 11

What is the nature of genetic code?

Answer 11

Triplet code/non-overlapping

Degenrative

Universal

Question 12

What does it mean that genetic code is triplet?

Answer 12

• The code in the base sequences is a simple triplet code
• It is a sequence called a codon
• Each codon codes for an amino acid

Question 13

What does it mean that genetic code is degenerative?

Answer 13

There are more potential codons that amino acids
(64 potential and 20 amino acids)
- this means some amino acids can be coded by more than one codon.

Question 14

What does it mean the genetic code is universal?

Answer 14

All organisms use the same code

Question 15

Describe DNA extraction

Answer 15

• Grind sample in pestle and motar - breaks down cell walls
• Mix sample with detergent - breaks down cell memebrane
• Add salt - breaks hydrogen bonds between water & DNA
• Add protease enzyme - break down proteins
• Add ethanol - cause DNA to precipitate out
  DNA seen as white strands forming between sample and layer of alcohol

Question 16

What are the two phases in TLC (thin layer chromotograpy) ?

Answer 16

• Stationary phase

- Mobile phase

Question 17

What determines the rate at which amino acids in the organic solvent move through the silica gel?

Answer 17

• Solubility

- The hydrogen bonds

Question 18

What is the equation for working out an Rf value (retention value)

Answer 18

Distance moved by the solute
——————————————
Distance moved by the solvent