8: Bacterial Genetics

Question 1

Define auxotroph

Answer 1

A microorganism that requires an organic growth factor. Ex. Amino acid

Question 2

Define Bacterial Transformation

Answer 2

Mechanism of horizontal gene transfer in which naked DNA is taken up by the recipient cell. (Usually from environment)

Question 3

Define Conjugation

Answer 3

Mechanism of horizontal gene transfer in which donor cell physically contacts the recipient cell.

Question 4

Define Genotype

Answer 4

The sequence of nucleotides in an organisms DNA

Question 5

Define Horizontal Gene Transfer

Answer 5

Transfer of DNA from one organism by a process other than reproduction.
Includes:
Conjugation
Transduction
Bacterial Transformation

Question 6

Define mutation

Answer 6

A change in the nucleotide sequence of a cell’s DNA that is passed on to daughter cells.

Question 7

Define Plasmid

Answer 7

A DNA molecule that replicates independently of the chromosome.

Question 8

Define Prototroph

Answer 8

A microorganism that does not require any organic growth factors.
(Opposite of auxotroph)

Question 9

Define Transduction

Answer 9

Mechanism of horizontal gene transfer in which bacterial DNA is transferred inside a phage coat.

Question 10

Define Transposable Element

Answer 10

Segment of DNA that can move from one site to another in a cells genome.

Question 11

Define vertical gene transfer.

Answer 11

Transfer of DNA from parent to offspring.

Question 12

Define strain(s).

Answer 12

Genetic variants within a species.

Question 13

What are the two mechanisms bacteria use to change their genetic code?

Answer 13

Mutation, horizontal gene transfer.

Question 14

What’s the convention for writing strains of bacteria?

Answer 14

Question 15

Define spontaneous mutation. What does this mean for a colony?

Answer 15

Random genetic change that results from normal cell processes and are passed to offspring.
This means colonies usually are never exactly identical.

Question 16

Define reversion.

Answer 16

A mutation that reverts a strain back to its original, non-mutated state.

Question 17

Define Base-pair substitution. How can this occur?

Answer 17

A type of point mutation that replaces one of the base pairs with another.
This can occur from DNA polymerase incorporating an incorrect base.

Question 18

Define Synonymous mutation.

Answer 18

Incorporation of the incorrect nucleotide creates a codon that encodes the same amino acid as the original code.
NOT necessarily a silent mutation as the mutation can still cause a change that affects efficiency of translation.

Question 19

Define missense mutation.

Answer 19

Incorporation of the incorrect nucleotide creates a codon for a different amino acid.

Question 20

Define nonesense mutation

Answer 20

Incorporation of the incorrect nucleotide creates a stop codon.
Often making protein non-functional.

Question 21

Define frameshift mutation

Answer 21

Adding or subtracting anything amount of amino acids that isn’t 3. Change the reading frame for mRNA so an entirely different set of codons is translated.

Question 22

Explain transposition. (Non-homologous recombination)

Answer 22

Integration into new location through a process that does not require a similar nucleotide sequence in the region of recombination.
Simply insertion into a stretch of DNA, does NOT replace the existing sequences.

Question 23

Define what insertional inactivation is.

Answer 23

The outcome when transportation(non-homologous recombination) occurs and the gene is disrupted by the event, so the gene becomes non-functional.

Question 24

Define induced mutation.

Answer 24

Genetic changes that occur due to an influence outside of a cell. Ex. Radiation or exposure to chemicals.

Question 25

Define mutagen

Answer 25

An agent that induces the change/mutation of a bacteria.

Question 26

Why are alkylating agents so mutagenic?

Answer 26

They add a methyl group/ other alkyl group onto bases. Which can cause mispairing.

Question 27

Define Base Analogs

Answer 27

Structurally resemble the bases, but have different hydrogen bonding properties.These can be mistakenly used in place of the real bases. making complementary strand possible the wrong base as well.

Question 28

Define intercalating agents

Answer 28

They Increase the frequency of frameshift mutations because they can insert(intercalate) between adjacent bases of DNA. Pushing nucleotides apart, making them more susceptible to insertions/deletions.

Question 29

Define transposons

Answer 29

A type of transposable element, more detailed answers in further FC’s.

Question 30

How does UV exposure affect DNA? Why is it considered mutagenic?

Answer 30

Causes covalent bonds to form between adjacent thymine dimers.
Making the strand unable to properly fit into a double helix. Stopping replication and transcription.
It’s major way of being mutagenic results form the cells attempt to repair the damage by SOS repair.

Question 31

How does X Rays exposure affect DNA? Why is it considered mutagenic?

Answer 31

Causes single and double strand breaks in DNA, and they damage nucelobases.

Question 32

Start back up at section 8.4