Lecture 5

Question 1

Who was Archibold Garrod?

Answer 1

• 1902
• First to connect inherited human disorders to Mendels law of inheritance

Question 2

Alkaptonuria

Answer 2

• A condition in which urine darkens with air exposure
• Patients contain large amounts of homogentisic acid
• It can be inherited (autosomal recessive)
• Garrod theorised that the patients was missing a faulty enzyme (that breaks down this acid) as a result of faulty inherited DNA

Question 3

Beadle and Tatum experiment overview

Answer 3

• 1950s
• Study on how genetic material changes may effect metabolism

Question 4

Why was Neurospora the best subject?

Answer 4

• Haploid so it allows recessive genes to be shown
• Normal mould could grow without many nutrients as it makes its own using enzymes

Question 5

Experiment on neurospora?

Answer 5

1. Theory was that if they damage the DNA for an enzyme, the cells would not be able to survive without that particular nutrient
2. Irradiated mould with X-rays to create Auxotroph mutants
3. Grew the variants on range of nutrient lacking moulds and identified which amino acids allow the autrophs to grow

Question 6

“One-gene, one-enzyme?”

Answer 6

• Proposal that each enzyme was controlled by one gene.
• But not all gene products are enzymes? proteins?
• But some proteins are mad eup more than one polypeptide chain? One gene- one chain?

Question 7

How do genes specify proteins?

Answer 7

• Uses a “messenger” to transfer information from nuclei to cytoplasm
• Messenger is RNA

Question 8

RNA overview of structure

Answer 8

• Single strand
• Repeating units of ribose sugar, phosphate and bases

Question 9

Transcription

Answer 9

1. Does not require a primer for RNa polymerase to work, unlike DNA
2. RNA polymerase binds to the promotor region of DNA template strand and moves along, unwinding the double helix.
3. RNA polymerase catalyses the addition of ribonucletides to 3’ RNA end
4. Transcription stops when RNA polymerase reaches a termination sequence

Question 10

Crick and Brenner

Answer 10

• Proved that groups of 3 bases called Codons specifies for one amino acid
• 3 stop codons
• 1 start/methionine codon
• Redundent (amino acid can be coded by more than one codon)