lecture 4

Question 1

flow of genetic information

Answer 1

• information content of DNA is in nucleotides
• DNA inherited produces pecific traits by dictating synthesis of proteins
• proteins are links between genotype and phenotype
• gene expression = process DNA directs protein synthesis
• transcription and translation

Question 2

one gene, one enzyme hypothesis

Answer 2

• cells synthesis and degrade molecules in steps (metabolic pathway)
• different enzymes catalyse different steps; mutation causes interruption in pathways
• each gene dictates production of specific enzyme
• some proteins not enzymes (causing hypothesis revision)
• adapted to one gene-one polypeptide hypothesis

Question 3

nutritional mutants in neurospora

Answer 3

• bread mold to x-ray
• mutants unable to survive (inability to synthesis certain molecules)

Question 4

gene expression

Answer 4

• transcription: synthesis of RNA under direction of DNA (producing messenger RNA - mRNA)
• translation: synthesis of polypeptide (direction under mRNA taking place in ribosome)

Question 5

genetic code

Answer 5

• triplet code: series of non-overlapping three-nucleotide words (codons)
• 64 triplets; 61 code amino acids; 3 stops signals
• genetic code redundant but not ambiguous (no codon specifies more than 1 amino acid)
• stoppers = UAA; UGA; UAG
• start = AUG

Question 6

translation of code

Answer 6

• one of two DNA strands provide template for transcription
• during translation mRNA codons read 5’ -> 3’
• translation initiated at start codon; terminated at stop codon (reading frame)
• codons must be read in correct reading fram for specified polypeptide to be correctly produced

Question 7

evolution of code

Answer 7

• genes can be transcribed and translated after being transplanted from one species to the other