Dar

What is one human system that protects us from most infections?

immune system

Your physician had prescribed a β-lactam antibiotic for your sister. Your sister took biology in high school and is refusing to take the antibiotic because she says that it will affect osmosis in her cells. Which reason can you use to help your sister understand how the antibiotic will work?

β-lactam affects bacterial cell walls, and it can't affect human cells because they do not have cell walls.

What is responsible for genetic variation in bacteria?

-Mutations occur in the genome during binary fission. -Gene transfer from a different bacterial strain occurs. -Mutations produce new alleles, therefore new traits. *all of these*

Which group is at high risk group for MRSA?

-children in day care centers -individuals confined mainly to hospitals -individuals on military bases all of these

A change in allele frequencies in a population over time in response to environmental pressure is characteristic of _____

-directional selection -diversifying selection -natural selection -stabilizing selection

Treating and preventing infections by antibiotic-resistant bacteria can be accomplished by _____.

-reducing antibiotics in livestock feed -washing hands frequently -disinfecting common surfaces -researching new vaccines all of these

Beta-lactams include _____.

1. penicillin 2. cephalosporins 3. methicillin 4. cephalexin

MRSA sickens some 75,000 people in the United States each year and kills almost _____.

10,000

Drug-resistant staph strains first emerged in hospitals during the early _____.

1960s

Experts estimate that approximately _____ of the U.S. population (nearly 90 million people) is colonized by S. aureus.

30%−40%

Which of the steps of bacterial reproduction occurs first?

DNA is replicated.

Which step is NOT involved in bacterial reproduction?

Daughter cells stay attached.

Which of these is a harmful bacterium?

Salmonella

An antibiotic-resistant allele confers a fitness cost. What would you predict about the growth of the bacteria with the resistant allele compared to the growth of bacteria without the sensitive allele in the presence or absence of antibiotics?

The sensitive strain will have the highest fitness in the absence of antibiotic, and the resistant strain will have the highest fitness in the presence of antibiotic.

The differences in strains of Staphylococcus are contained in its DNA.

True

MRSA is caused by _____.

a drug-resistant form of Staphylococcus aureus.

The response of a population to environmental pressure so that advantageous traits become more common in the population over time is called _____.

adaptation

When a population shows an adaptation, it means that a population responds to an environmental pressure such that the presence of _____ traits _____ over time.

advantageous; increases

Chemicals that either kill bacteria or slow their growth by interfering with the function of the essential bacterial cell structures are _____.

antibiotics

Antibiotics _____.

are chemicals that interfere with the functioning of essential bacterial cell structures

A type of asexual reproduction in which one parent cell divides into two is called _____.

binary fission

How do β-lactam antibiotics kill sensitive bacteria?

by destabilizing the cell wall

What are the two major mechanisms by which bacterial populations generate genetic diversity?

by gene exchange and mutation

Beta-lactam antibiotics interfere with bacteria's ability to synthesize _____.

cell walls

If you carry staph of any strain but aren't sick, you are _____.

colonized

A sensitive S. aureus bacterium acquires a new gene that allows it to resist the effects of β-lactam antibiotics. What might the protein encoded by that gene do?

digest β-lactam antibiotics

The evolution of antibiotic resistance is an example of _____.

directional selection

Methicillin is currently used to treat staph infections.

false

The relative ability of an organism to survive and reproduce in a particular environment is known as _____.

fitness

A non-staph bacterium that is resistant to penicillin and a staph bacterium are found in the same host. After the bacteria grow and replicate, it is found that the staph bacteria is now penicillin resistant. This is likely due to _____ between the two bacteria.

gene transfer

Where is MRSA most likely to be a problem?

in the bloodstream

All of these statements are true about natural selection EXCEPT _____.

it works best in genetically uniform populations

Bacteria can become resistant to drugs by _____.

mutations and acquiring "resistance genes"

Differential survival and reproduction of individuals in response to environmental pressure that leads to changes in allele frequencies in a population over time is called _____.

natural selection

Which hypothetical antibiotic would treat bacterial infections by interfering with bacterial reproduction?

one that decreases cell membrane synthesis

If the cell wall of Staphylococcus aureus fails to form properly, water will enter the cell by the process of _____.

osmosis

A group of organisms of the same species living together in the same geographic area is called a(n) _____.

population

Which of the four regions of the body contain species of staph that are considered helpful?

skin

A type of natural selection in which organisms near the middle of the phenotypic range of variation are favored is _____.

stabilizing selection

In humans, very large birth weight babies and very tiny babies do not survive as well as midrange babies. What kind of selection is acting on human birth weight?

stabilizing selection

Which of these is a feature of both evolution and natural selection?

the change in allele frequencies over time in a population

What is the environmental pressure in the case of antibiotic resistance?

the presence or absence of antibiotics in the environment

Which of these is decreased when there is stabilizing selection?

the range of phenotypic variation

An organism's fitness depends on its environment.

true

Even though mutation rates for bacteria and humans are identical, bacteria are able to adapt more quickly to their environment than are humans.

true

The differences in strains of Staphylococcus are contained in its DNA.

true

There are more bacteria living in and on you than there are cells that make up the human body.

true

Which situation puts a healthy person at greater risk for a MRSA infection?

undergoing a medical procedure that weakens the immune system undergoing a procedure that causes a break in the skin being a child whose immune system is still maturing being elderly *all of these*

Which of these antibiotics is the drug of choice when a serious MRSA infection is present?

vancomycin

Antibiotic-resistant bacteria have _____ fitness in the presence of antibiotics.

very high