16. Microbial Genetics

Which of the following mutations, occurring just after the start codon in the mRNA is likely to have the most serious effects on the polypeptide product?

A single base substitution is LEAST likely to be deleterious (dangerous) when the change results in _____.

______ mutations occur randomly & ______ mutations are deliberate & occur due to an external source:

Why are mutation and recombination important in the process of natural selection and the evolution of organisms?

Classify the effects of the following mutations as missense, nonsense, or silent (use the genetic code table in the chapter to help you):

a. mRNA codon AUG is mutated to AUC

b. mRNA codon UAC is mutated to UAA

c. mRNA codon GGC is mutated to GGG

d. mRNA codon UAA is mutated to UAG

e. mRNA codon UGG is mutated to CGA

Assume a clinical sample yields a strain of S. aureus containing a plasmid that encodes two antimicrobial-resistance genes. How did the bacterium most likely acquire these new resistance genes?

a. The strain was intrinsically resistant.

b. The strain obtained the genes through horizontal gene transfer.

c. The strain acquired the genes by a random mutation.

d. The strain picked up the genes by an efflux pump.

e. The strain acquired the genes through cell division events.

Insertions and deletions in the genetic code are also called ___________ mutations.

Which of the following are called “jumping genes”?

a. Hfr cells

b. Transducing phages

c. Palindromic sequences

d. Transposons

Before mutations can affect a population permanently, they must be __________ .

a. lasting

b. inheritable

c. beneficial

d. all of the above

Three effects of point mutations are ___________ , ___________ , and ____________ .

Some antibiotics activate phage genes. MRSA releasing Panton-Valentine leukocidin is a toxin that can cause a life-threatening disease. Why can such a disease develop following antibiotic treatment?