Pathogenic Microbiology Test I

Front 1

What are two ways bacteria may incorporate extra genetic information?

Back 1

plasmids or bacteriophages

Front 2

Where does DNA replication begin?

Back 2

DNA replication begins at a specific sequence in a chromosome called the OriC

Front 3

What is the role of topoisomerase?

Back 3

Topoisomerase relieves tosional stress on the chromosome during replication. They make important targets for some antibiotics.

Front 4

What is an example of a topoisomerase?

Back 4

DNA gyrase

Front 5

What is the role of helicase?

Back 5

unwinds the DNA strand.

Front 6

What is the role of primase?

Back 6

Primase synthesizes the primers needed to start replication.

Front 7

What is the role of DNA polymerase?

Back 7

Synthesizes DNA, but cannot do so without primase.

Front 8

What is an operon?

Back 8

One or more genes under the control of a promoter and an operater.

Front 9

What does it mean to be polycistronic?

Back 9

Operons encoding many genes.

Front 10

What is a promoter?

Back 10

A region upstream of the genes where RNA polymerase binds to initiate transcription.

Front 11

Describe the steps that must be taken in order for an operon to be transcribed.

Back 11

a sigma factor must bind to RNA Polymerase. They then bind to a promoter, which activates the operator, then transcribes the operon.

Front 12

What is sigma 70?

Back 12

A sigma factor located in activated in normal, actively growing cells.

Front 13

What is RpoS?

Back 13

RpoS is a sigma factor that is activated when the cell is stressed, but enhances the binding of RNA polymerase to promoters for operons involved in the stress response.

Front 14

Describe activators.

Back 14

Bind to a DNA sequence near the promoter and help the RNA polymerase bind.

Front 15

Repressors

Back 15

Bind to operator and prevent transcription.

Front 16

Describe what happens to the Lac Operon when glucose is present but not lactose

Back 16

LacI acts as a repressor and binds to the operator protein, therefore inhibiting transcription of the lactose gene.

Front 17

Describe what happens to the lac operon when both glucose and lactose are present.

Back 17

When lactose is present, it binds to the Lac I repressor and changes its conformation so that it can no longer bind to the prevent transcription. However, RNA polymerase has a low affinity for the promoter so expression occurs at a low level.

Front 18

Describe what happens to the lac operon when only lactose is present.

Back 18

When glucose levels are low, cAMP levels are high in the cell. cAMP binds to a catabolite activator protein which adheres a little upstream the promoter region. This enhances the binding of polymerase and increases efficiency.

Front 19

What is codon degeneracy?

Back 19

When there are more codons than amino acids. The same amino acid refers to a different sequence of codons.

Front 20

What is the role of tRNA?

Back 20

tRNA contains the anti-codon sequence complementary to the mRNA codon and the complememntary amino acid. It is the adapter between mRNA and the peptide sequence.

Front 21

When does translation occur?

Back 21

In prokaryotes, translation occurs as the mRNA is being transcribed.

Front 22

What is a silent mutation?

Back 22

A mutation at the nucleotide level that does not change the amino acid.

Front 23

What help minimize the effect of a silent mutation?

Back 23

codon degeneracy.

Front 24

What is a neutral mutation?

Back 24

When a nucleotide mutation results in a different amino acid, but the amino acid has the same properties as the old amino acid. Therefore, the protein is not significantly affected.

Front 25

What is a missense mutation?

Back 25

When a nucleotide mutation results in a different amino acid and the amino acid has a different property to the old amino acid. Therefore, the protein function could be significantly impacted.

Front 26

What is a nonsense mutation?

Back 26

Changes a codon to a stop codon. This prematurely ends peptide synthesis.

Front 27

What is another name for a protein with a nonsense mutation?

Back 27

"truncated protein" is one that isn't a complete protein.

Front 28

What is a frameshift mutation?

Back 28

An insertion or deletion that is not in multiples of 3. Therefore, the reading frame for the gene is changed.

Front 29

What are the two different types of recombination?

Back 29

homologous and non-homologous.

Front 30

What is homologous recombination?

Back 30

recombination of DNA sequences having nearly the same nucleotide sequence. This is usually used to repair damaged DNA.

Front 31

What is non-homologous recombination?

Back 31

insertion of DNA that is different from that DNA that is already there. This is usually used for evolution of new and novel traits in bacteria.

Front 32

What are plasmids?

Back 32

Extrachromosomal, self-replicating DNA

Front 33

What are conjugative plasmids?

Back 33

plasmids that code for functions tha tpromote the transfer from a donor to a recipient.

Front 34

What is a virulent phage?

Back 34

AKA lytic phage. Replicates to large numbers before lysing the bacterial cell and releasing viral particles.

Front 35

What is a temperate phage?

Back 35

These can have a lytic cycle or become incorporated into chromosome without causing cell death.

Front 36

What is the term for a temperate phage that beomes incorporated into the bacteral genome?

Back 36

prophage

Front 37

What determines the "sex" of a bacterium during conjugation?

Back 37

A bacterium with a plasmid is known as a "donor," male, or F+, whereas the bacterium lacking the plasmid is the "recipient," female, or F-.

Front 38

Name the three types of conjugal transfer.

Back 38

F+ to F-
Hfr to F- when the plasmid becomes incorporated into the chromosome (High frequency for recombination)
F' to F- when plasmid contains some of the chromosome

Front 39

What is the end product of the F+ to F- transfer?

Back 39

A donor and Recipient pair become to Donors (Both have a plasmid)

Front 40

How does a Hfr to F- transfer its DNA to the recipient?

Back 40

It transfers the chromosomes first, and the plasmid last. Although the plasmid gets incorporated into the DNA, it rarely gets transferred completely to another cell.

Front 41

Briefly describe F' to F- transfer.

Back 41

When the plasmid contains some of the chromosome.

Front 42

Describe transformation.

Back 42

Competent bacteria can uptake naked DNA from dead cells.

Front 43

What is transduction?

Back 43

Transfer of bacterial DNA by bacterophages.

Front 44

How does transduction occur?

Back 44

A particular gene is transferred due to is close proximity to a lysogenic phage in the chromosome.