Bacterial Genetics I

Front 1

Resistance to antibiotics can arise by mutation in DNA that _____ or _____.

Back 1

Changes the biosynthetic enzyme so it no longer binds the drug
OR
Increases the amount of enzyme so that some enzymes are not inhibited by the drug

Front 2

Describe genotype.

Back 2

The genetic code/sequence of the genome of an organism.

Front 3

G+C content is a genotypic/phenotypic property.

Back 3

Genotypic

Front 4

Describe phenotype.

Back 4

Observable or measurable traits of an organism.

Front 5

Give examples of phenotypic properties.

Back 5

Drug resistance
Growth rate
Colony size
Metabolic capacities

Front 6

True or False.
Bacterial mRNA is relatively unstable and is rapidly degraded by nucleases often in the 3' --> 5' direction.

Back 6

True

Front 7

Translation of bacterial mRNA starts at an AUG or GUG which is part of the ribosome binding sequence that is called _________.

Back 7

Shine-Dalgarno sequence

Front 8

______ is found at the amino terminus of a polypeptide.

Back 8

f-Met

Front 9

What are Ochre, Opal, and Amber?

Back 9

The three nonsense codons that terminate translation.
(UAA, UGA, UAG)

Front 10

Mistakes in base pairing during DNA replication lead to changes in the DNA sequence called _________.

Back 10

mutations

Front 11

What are two other ways mutations can arise?

Back 11

Insertions and rearrangements of DNA segments

Front 12

Base substitutions can lead to three different types of mutation. They are:

Back 12

Missense
Silent
Nonsense

Front 13

Deletion or insertion of single bases results in ________ mutation.

Back 13

Frameshift mutation

Front 14

True or False.
Duplications of 3, 6, 9, etc. bases will lead to insertions of 1,2,3, etc. tandem amino acids.

Back 14

True

Front 15

Insertion of 3,6,9, etc. bases will result in insertion of 1,2,3 amino acids but the _________ will be maintained.

Back 15

Reading frame

Front 16

Wild-type phenotype can also be restored by a process of ________.

Back 16

Suppression

Front 17

What is suppression?

Back 17

Restoration of wild-type phenotype due to a second-site mutation that reverses the mutant phenotype.

*Ex. Suppression can restore the full length of a truncated protein but may/may not insert the amino acid specified by the wild-type.

Front 18

What were the two important hypotheses about the nature of mutagenesis in bacteria?

Back 18

1. Mutations arise from a directed process that allow bacteria to adapt to specific conditions.
2. Mutations arise randomly in bacterial populations without any directed process or feedback from the selection conditions.

Front 19

Describe the experiment that proved the spontaneous nature of mutagenesis in bacteria.

Back 19

Bacteria grown in bulk culture then spread on plates seeded with T1 phage had the SAME # of colonies resistant to the T1 phage.
Bacteria grown in individual cultures had great variation in the # of T1 phage resistant colonies.

Therefore, mutation that caused T1 resistance arose from spontaneous mutation and NOT from a directed process.

Front 20

The proofreading subunit is called ____ is part of the DNA pol III complex and removes mispaired bases from the growing strands during replication.

Back 20

Epsilon

Front 21

Oxidative damage converts G residues to 8-oxoG residues. This will pair with ___ resulting ina change from GC to TA base pair.

Back 21

Adenine

Front 22

Homologous recombination plays an important role in the repair of _____.

Back 22

Double strand breaks (DSB)

Front 23

DSB repair involves invasion by the ___end of one of the broken strands into an intact dsDNA coply that exists during ____.

Back 23

3' end

during chromosome replication

Front 24

Name two well-studied examples of site-specific recombination.

Back 24

Phase inversion

Lysogenization

Front 25

Phase inversion is brought about by a specific recombinase protein called ___ and will cause changes in expression of bacterial _____.

Back 25

Hin
Flagellin

Front 26

________ are DNA elements that have the ability to jump between different DNA molecules in cells.

Back 26

Transposons

Front 27

Name the 2 categories of transposons.

Back 27

Insertion sequences

Complex transposons

Front 28

True or False.

All transposons encode transposase.

Back 28

True.

Transposase is the enzyme that catalyzes the cutting and insertion events.

Front 29

Where is transposase gene located?

Back 29

It is found in the core region of insertion sequences.

Front 30

All transposons have _____ ____ of DNA that are recognized by the transposase.

Back 30

inverted repeats

Front 31

True or False.

Only some transposons will create a direct repeat of the target DNA into which they insert.

Back 31

FALSE.

ALL transposons will create a direct repeat of the target DNA into which they insert.

Front 32

How are complex transposons different from insertion sequences?

Back 32

Complex transposons contain 2 insertion sequences that surround a core region that contains genes for antibiotic resistance. The 2 insertion sequences and the core transpose as one unit.

*see diagram pg. 57 in syllabus

Front 33

True or False.

Transposon insertions can disrupt reading frames and may inactivate the function of the genes into which they insert.

Back 33

TRUE

Front 34

The recombinase that catalyzes VDJ joining to generate antibody diversity probably evolved from a _______.

Back 34

Transposase

Front 35

Agents such as _____ induce DNA repair pathways.

Back 35

UV light