Intro to clinical micro biology Exam II

Does the following occur in both prokaryotes and Eukaryotes

Translation
DNA Replication
Transcription

yes

translation of mRNA into protein begins before transcription is complete in

prokaryotes only

In prokaryotes, the mRNA transcript encounters ribosomal parts immediately as it leaves the DNA.

true

Operon

cluster of genes that perform related functions

Intron

non-coding regions in mRNA

exons

coding regions of mRNA

when introns are removed and extrons are joined together

before translation

double stranded DNA

genetic material in bacteria

DNA replication in bacteria begins here

single origin that proceeds in both directions

gyrase

mediates super coiling

primase

synthesizes RNA primers

Ligase

Seals nicks in DNA backbone during synthesis and repair

Helicase

unzips the DNA double helix

DNA polymerase III

adds bases to growing DNA chain

DNA polymerase I

removes RNA primers, replaces with DNA bases

mutations

Population changes, and thus evolution, result from variations called genetic

spontaneous mutations

Random change in the DNA arising from errors in replication that occur without a known cause

induced mutation

Result from exposure to known mutagens, which are primarily physical or chemical agents that damage DNA

substitution mutation

Changing of single base in the DNA code that may result in the placement of a different amino acid

frameshift mutation

Addition or deletion of bases that changes the reading of mRNA codons

Conjugation

direct transfer of DNA from donor cell to recipient cell

transduction

transfer via phage

transformation

uptake of free DNA

plasmids can

replicate independently of the chromosome

recombinant organism

organism that that contains genes from another organism

if a plasmid has an R factor

that bacteria will be resistant to an antibiotic

importance of conjunction and other forms of recombination

they create genetic diversity

F⁺ cell

have a plasmid and are donors in conjugation

The F pilus binds to

a protein appendage that attaches the two cells

The plasmid is mobilized for transfer when

an endonuclease cleaves it at the origin of replication.

for that plasmid DNA is transferred in

single-stranded form

In the beginning of transformation, which molecules binds to the target cell?

Double-stranded DNA

During the entry of the donor DNA into the recipient cell,

one strand is broken down by nucleases.

The donor DNA in bacterial transformation

pairs with a homologous region of the recipient DNA.

Mismatch repair is activated by

any difference between the nucleotide sequence in the donor and recipient DNAs

As a result of mismatch repair during transformation..

cells may have either original DNA or donor DNA in them.

After entry of the bacteriophage into the host cell, a phage enzyme

breaks the host DNA into fragments.

During maturation or formation of phage particles…

a few phage heads may surround fragments of host bacterial DNA.

In transduction, bacterial DNA is transferred to a new cell when

it is injected by a virus

When the bacteriophage transfers bacterial DNA into a recipient bacterial cell,

it can integrate into the chromosome.

generalized transduction

Random fragments of disintegrating host DNA are taken up by the phage during assembly

specialized transduction

Highly specific part of the host genome is regularly incorporated into the virus

Restriction enzymes

make staggered cuts at specific sequences in DNA in both donor DNA and the plasmid.

function of DNA ligase in cloning a gene

It seals the sticky ends of the desired DNA fragments with the cohesive ends of the plasmid.

plasmids are put into bacterial cells by

transformation

DNA library

collection of clones DNA fragments stored in host cell

benefits of genotypic methods to identify pathogens

fast and more precise than phenotypic
don’t have to culture

DNA probes are used to

locate specific DNA nucleotide sequences

For DNA probes to hybridize,

DNA strands must be homologous, having regions with similar or identical nucleotide sequences.

PCR

Polymerase Chain rxn

general purpose of the PCR process

Make many copies of a small target piece of DNA

role of Taq polymerase

catalyzes the synthesis of the new DNA chains

why taq polymerase is specifically used in PCR

it’s stable at higher temperatures

Why is the DNA heated to over 90 degrees Celsius to start PCR

Heat denatures the DNA

Why is the DNA cooled slightly after it is denatured in PCR

To allow the primers to anneal to their complementary sequence on the target DNA

what’s used to automatically expose the polymerase chain reaction to repetitive steps, yielding large amounts of DNA in a short period of time

Thermal cycler

Because the sequence of DNA nucleotides is unique for each organism, DNA fingerprinting may now be used to emphasize these differences and display the entire genome in a pattern for comparison

true

recombinant DNA technology

The deliberate removal of genetic material from one organism and combining it with the genetic material of another organism is a specific technique called

What type of genetic transfer occurs during specialized transduction?

Only specific bacterial genes located near the phage insertion site are transferred.

What happens in an inducible operon when the inducer is present?

 

The inducer binds to the repressor, allowing transcription to proceed.

What is the key factor that determines the success of nucleic acid hybridization?

The ability of complementary nucleic acid strands to form stable base pairs.

In bacterial replication, what does the term semi-conservative replication refer to?

Each newly formed DNA molecule consists of one original parental strand and one newly synthesized strand.

What is the primary purpose of PCR (Polymerase Chain Reaction)?

purpose of amplifying specific segments of DNA

Which enzyme is responsible for unwinding the bacterial DNA helix during replication?

Helicase

Which of the following is an example of a mutation being retained due to selective pressure?

Bacteria developing antibiotic resistance during treatment.

How does PCR differ from Sanger sequencing?

PCR amplifies DNA, while Sanger sequencing determines the nucleotide sequence.

chemical agents

Use of a gaseous or liquid microbicide to destroy microorganisms

mechanical removal

Use of a filter to remove microorganisms from liquids or air

physical agents

Use of heat or radiation to destroy microorganisms

example of antisepsis

Use of chlorohexidine to prepare the skin prior to surgery

example of disinfection

Applying an antimicrobial chemical to your lab bench following completion of lab activities

example of sterilization

Use of an autoclave to prepare surgical instruments

asepsis

Wearing gloves and a face mask while performing surgery

sanitization

Cleaning eating utensils and plates in a restaurant

What is the relationship between microbial load and sterilization?

As microbial load increases, the time it takes for sterilization also increases.

The shortest length of time required to kill all test microbes at a specified temperature is the thermal death ____

time

five primary modes of actions of antimicrobial drugs

Inhibition of cell wall synthesis
Disruption of cell membrane structure or function
Inhibition of protein synthesis
Blocking key metabolic pathways
Disruption of structure or function of nucleic acids (DNA/RNA)

Penicillin targets the bacterial cell wall making it effective against gram ___ organisms

positive

An antimicrobial drug that is effective against a very diverse array of bacteria is described as ________ spectrum

broad

a drug that is very selective for a just a few different types of bacteria is described as _________blank spectrum

narrow

inhibition of protein synthesis

Aminoglycoside antibiotics, Streptomycin, Tetracycline

Why are antibiotics that attack the cell wall considered bactericidal?

A weakened cell wall leads to cell lysis

three most important considerations in antibiotic selection

condition of patient, The antibiotic susceptibility profile, The nature of the microorganism causing the infection

primary goal of antibiotics

To destroy the infective agent &
To be nontoxic to the host and produce no side effects

ratio of toxic dose to minimum therapeutic doese

therapeutic index

toxic effects of drugs are most commonly seen in these organs

Liver and kidneys

three major mechanisms by which antimicrobial resistance genes are shared and spread among microbial populations

Conjugation,
Transduction,
Transformation

Most body surfaces and outer openings of body tracts are normally colonized by a population of microorganisms referred to as the

microbiota

While most of these normal residents are harmless or beneficial, there are a small number of potential ______ that can also exist normally in the body

Pathogens

What does a high therapeutic index indicate about a drug?

The drug has a wide margin of safety between its effective dose and toxic dose

What is the primary spectrum of activity for polymyxins?

Primarily effective against Gram-negative bacteria

What is the goal of antimicrobial susceptibility testing?

To determine the pathogen’s response to various antimicrobics.

What is the primary mechanism by which alcohols kill microbes

They denature proteins and disrupt cell membranes by dissolving lipids.

Triclosan is a type of phenolic antimicrobial agent commonly found in:

 

Antibacterial soaps and personal care products

How do drug pumps contribute to antibiotic resistance?

Bacteria actively expel antibiotics from the cell before they can exert their effects.

How do detergents and soaps contribute to microbial control?

They emulsify lipids in microbial membranes, leading to cell lysis.

The collective total of genetic material from all microbiota

human microbiome

A newborn acquires normal microbiota during the birthing process and through contact with family, health care providers, food, and their environment.

true