Biology CH 13

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

10,000

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 of these is a harmful bacterium?

Salmonella

On which part of your body is normal staph most likely to reside?

Skin

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.

S. aureus can be transferred from person to person by _____.

all of these (direct contact with contaminated skin the use of soap and towels contaminated surfaces)

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

all of these (directional selection diversifying selection natural selection stabilizing selection)

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

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

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

all of these (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)

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

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

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

Fitness is determined by the interaction between _____ and the environment.

phenotype

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

An organism's fitness depends on its environment.

true

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

true

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

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.