Staphylococcus aureus has become resistant to penicillin, methicillin, and now possibly to vancomycin. Since bacteria do not sex
ually reproduce, genetic recombination does not introduce new alleles into the genome. Bacteria do mutate at a high rate and can also swap genetic material through horizontal gene transfer. How did S. aureus acquire resistance in each instance?
1 answer:
Answer:
S. aureus acquire resistance by :
1) Beta-lactamase production.
2) Changes in penicillin-binding protiens (PBP) (mecA genes encode these altered PBPs )
3) Genes encoding the enzymes substituting D-lactate for D-alanine in the peptidogylcan.
Explanation:
More than 90% strains of Staphylococcus aureus contains plasmids which code for <u>beta- lactamases</u> which cause the enzymatic hydrolysis of the beta lactam ring resulting in the loss of antibacterial activity. (Resistance against penicillins )
Some of the strains of S.Aureus are resistant to beta lactamase resistant penicillins such as methicilin (MRSA) and nafcillin (NRSA) by virtue of <u>changes in the penicillin-binding protien (PBP)</u> in their cell membrane.
Some strains of S.Aureus are resistant to Vancomycin (VRSA) and they acquire this resistance by some genes located in a transposon on a plasmid and encode the enzymes that<u> substitute D-lactate for D-alanine in the peptidoglycan.</u>
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Answer:
0%
Explanation:
This question involves two distinct genes; one coding for seed shape and the other for seed colour. The allele for you seeds (R) is dominant over the allele for wrinkled seeds (r) in the first gene while the allele for yellow seeds (Y) is dominant over allele for green seeds (y).
In a cross involving RRYY (homozygous dominant for both traits) and RrYy (heterozygous for both genes), the following allelic combinations of gametes will be produced:
RRYY- RY, RY, RY, RY
RrYy- RY, Ry, rY, ry
Using these gametes in a punnet square (see attached image), 16 possible offsprings will be produced. The genotypes of the offsprings in the ratio 1:1:1:1 will be:
RRYY (4)
RRYy (4)
RrYY (4)
RrYy (4)
According to the question, offspring that have wrinkled seeds and yellow seed color will have genotype: rrYY or rrYy.
This genotype is not one of those that will be produced by the cross between a RRYY and RrYy parent. Hence, the probability of having an offspring with wrinkled seeds and yellow seed color is 0%
