Prokaryotic genes

Question 1

Bacterial genes

Answer 1

• Haploid
• One copy of each gene on a single circular chromosome
• No different tissues
• Can switch genes on and off

Question 2

Prokaryotic gene structure

Answer 2

• Promoter: sequences in the DNA required for expression and regulation of a gene
• Transcribed region: sequences are included in mRNA and include more than one open reading frame (operon)
• Terminator sequence: end of gene or operon.

Question 3

mRNA structure

Answer 3

• 5’ UTR: 5’ untranslated region located before the AUG start codon
• Translated region: start codon then a ribosome binding site (RBS)
• Terminator sequence: loop structure which gives mRNA stability

Question 4

What is the sigma factor?

Answer 4

Recognises the promoter and tells RNA where to start working

Question 5

Negative gene regulation

Answer 5

Repressor on operator prevent transcription

Question 6

Positive gene regulation

Answer 6

Activator is required for transcription

Question 7

Why is the promoter negative (-35 to -10) on a coding strand?

Answer 7

Because transcription starts at +1

Question 8

Prokaryotic translation

Answer 8

Ribosome binds to ribosome binding site (RBS) and initiates protein synthesis at start codon (ATG) or AUG for mRNA

Question 9

Bacterial gene organisation

Answer 9

Sets of related genes are organised into operons where each operon has 1 promoter

Question 10

Transcription of RNA

Answer 10

RNA can start transcription without nucleic acid (primer)

Question 11

Intrinsic termination

Answer 11

Inverted repeat in gene followed by a polyA region, transcription stalls and RNA polymerase separates with RNA

Question 12

What is Rho?

Answer 12

A terminator protein

Question 13

Rho-dependent termination

Answer 13

Rho pulls out transcript and acts as a motor to run along the RNA molecule

Question 14

What are polyribosomes?

Answer 14

Multiple ribosomes that bind to a transcript in the nucleoid resulting in copies of new proteins from one RNA molecule