Lecture 36. Prokaryotic Genetics

Question 1

What is bacterial genetics?

Answer 1

Bacterial genetics is the study of the mechanisms of heritable information in bacteria, their chromosomes, plasmids, transposons and phages

Question 2

What proportion of DNA on earth is bacteria DNA?

Answer 2

~30%

Question 3

How many bacterial cells are there in the human body?

Answer 3

Approximately the same number as eukaryotic cells

Question 4

What is the bacterial genome?

Answer 4

A single circular, double stranded DNA chromosome

Question 5

How long is the length of DNA in an E. coli?

Answer 5

About 1 mile

Question 6

How do bacteria asexually reproduce?

Answer 6

Binary fission

Question 7

What is the generation time of E. coli?

Answer 7

~20 mins

Question 8

When was E. coli adapted as a model organism?

Answer 8

1940s

Question 9

What is wild type E. Coli?

Answer 9

A phototroph (does not require special nutritional factors)

Question 10

What are auxotrophic mutants of E. Coli impaired in?

Answer 10

Some metabolic capabilities

Question 11

What do biosynthetic auxotrophs require in order to grow?

Answer 11

Additional nutrients to synthesise an amino acid, a nucleotide or a vitamin

Question 12

What can’t catabolic auxotrophs do?

Answer 12

Catabolic auxotrophs have lost the ability to catabolise some carbon source

Question 13

Why are catabolic auxotrophs rarely a problem?

Answer 13

Glucose is the carbon source of choice

Question 14

Consequences of possessing any mutation involved in the ability to metabolise glucose?

Answer 14

Usually death

Question 15

What are housekeeping genes?

Answer 15

Genes essential for survival

Question 16

What are 4 examples of housekeeping genes in E. coli?

Answer 16

Genes involved in DNA replication, Transcription and Translation, Cell Division and Glycolysis

Question 17

What are conditional lethal mutants?

Answer 17

Mutations that are lethal in some conditions (repressive conditions) but not in other conditions (permissive conditions)

Question 18

What are temperature sensitive mutants (ts mutants)?

Answer 18

Mutants that only grow at a permissive temperature (usually 30°C for E. coli and not at a restrictive temperature (37°)

Question 19

What are cold sensitive mutants (cs mutants)

Answer 19

The opposite of ts mutants e.g., they might grow at 37°C but not at 30°C.

Question 20

In gene annotation, what do three lower case letters indicate?

Answer 20

Three lower case letters indicating a biochemical pathway of process in which the gene product is involved

Question 21

In gene annotation what does the capital letter after the three lower case letters denote?

Answer 21

The actual gene

Question 22

In gene annotation, what do the numbers after the capital letter denote?

Answer 22

The allele

Question 23

In gene annotation, what must the letters and numbers be in?

Answer 23

Italics

Question 24

Nomenclature of phenotype

Answer 24

Strain phenotype described using same three letter mnemonic as genotype
First letter is capitalised, three letters not italicised
Thr- = requiring threonine (superscript -)
Leu+ = not requiring leucine

Question 25

In nomenclature, what do three letters code for?

Answer 25

Amino acids, common carbon sources, nucleotides and vitamins

Question 26

Terminology: Wild type

Answer 26

Normal species

Question 27

Terminology: Mutant

Answer 27

Organism whose genome carries a mutation with respect to the wild type – referred to as a strain

Question 28

Terminology: Phenotype

Answer 28

All observable properties

Question 29

Terminology: Mutation

Answer 29

Inheritable change in the base sequence of nucleic acid

Question 30

Terminology: Genotype

Answer 30

Defined by actual sequence of DNA

Question 31

Terminology: Allele

Answer 31

Sequence variant of a gene

Question 32

Terminology: Mutagenesis

Answer 32

Process by which mutants are produced

Question 33

Terminology: Mutagens

Answer 33

Chemical and physical agents which cause mutations. Many are also harmful to humans so take care when using these

Question 34

What occurs when an anabolic pathway is lost?

Answer 34

Losing this pathway leads to loss of ability to make the molecules

Question 35

What occurs when a catabolic pathway is lost?

Answer 35

Losing this pathway leads to loss of ability to break down the molecules