Chapter 8: Microbial Genetics

Assume a cell is grown in a culture medium containing radioactively labeled thymidine. After three cell divisions, what percentage of the cells would contain the radioactive label?

100%

For the peptide with the amino acid sequence, proline-alanine-glycine (pro-ala-gly), the DNA template strand could have the sequence

GGC CGA CCG

what is the most likely to yield a recombinant cell after mating

Hfr cell transfers to F- cell

what is true of transduction

a virus is required for transfer of genetic material

in E. Coli, Hfr cells

can pass main chromosome genes to a recipient cell

what is a method of vertical gene transmission

cell visions

what requires cell-to-cell contact

conjugation

Genes whose products are constantly expressed are __________.

constitutive

Most amino acids are encoded by several different codons. This is referred to as the __________ of the genetic code.

degeneracy

what statement is NOT true of translation

each amino acid is coded for by a single codon

True or false: In E. coli, the presence of lactose is necessary and sufficient for induction of the lactose-utilization genes.

false

True or false: The F factor plasmid allows bacteria to grow on unusual carbon sources.

false

True or false: The term phenotype is used to describe all of the organism's genetic information.

false

True or false: mutations are always harmful to cells

false

The transfer of genetic information between organisms through processes such as transduction or conjugation is called __________ gene transfer.

horizontal

The process by which normally repressed genes are "turned on" is referred to as __________.

induction

the chemical 5-bromouracil is a mutagen because it

is similar to thymine in structure but not base-pairing ability

what is NOT a step in translation

joining of the Okazaki fragments

In DNA synthesis, the strand that is synthesized continuously is the __________ strand.

leading

The major source of the genetic diversity among microorganisms upon which natural selection operates is __________.

mutation

what is not true of base substitutions?

mutations rarely involve base substitutions

The codons UAA, UAG, and UGA signal the end of a gene sequence and are known as __________ codons.

nonsense (stop)

what is NOT true about DNA replication

only one strand of the parent DNA serves as a template for a newly synthesized complementary strand

An __________ is a set of structural genes and the operator and promoter sites that control their transcription.

operon

when the antibiotic chloramphenicol binds to the 50S portion of the ribosome, the effect is to

prevent the ribosome from moving along the mRNA strand

To begin transcription, RNA polymerase binds to a region on DNA known as the __________.

promoter

The spontaneous mutation rate for most organisms is low because of __________ by DNA polymerase during DNA replication.

proofreading

a frameshift mutation in a gene encoding a protein usually

results in the production of a nonfunctional protein

Which of the following processes is involved in the production of diphtheria toxin by C. diphtheria or erythrogenic toxin by Streptococcus pyogenes?

specialized transduction

both transcription and DNA replication involve

synthesis using a DNA template

what is NOT true for positive (direct) selection

the procedure detects altered genotypes regardless of the phenotype

in the lac operon of E. coli

the repressor protein binds to the operator in the absence of lactose

for the amino acid aspartic acid (asp)

the sequence of the DNA template would be CTG

Consider the polypeptide sequence encoded by the following DNA. TACAAAGAAATT If base number 6 is changed to G, how will this affect the polypeptide?

there will be no change in the polypeptide

Consider the polypeptide sequence encoded by the following DNA: TACAAAGAAATT. If base number 6 is changed to G, how will this affect the polypeptide?

there will be no change in the polypeptide

what is NOT true of plasmids

they are essential for survival of the organism in most situations

the Ames test is used

to determine if a chemical is mutagenic and possibly carcinogenic

Your lab partner has mixed a dead tryptophan+ strain of Bacillus subtilis with a live tryptophan- strain and observes that her B. subtilis culture is now tryptophan+. The most likely explanation for this is

transformation

Small stretches of DNA that can move within a genome are referred to as __________.

transposons

True or false: An operon consists of structural genes that encode enzymes along with the necessary regulatory genes.

true

True or false: Antibiotic resistance can be carried on plasmids and passed from bacterium to bacterium during conjugation.

true

True or false: Codons of mRNA temporarily bond to anticodons of tRNA during translation.

true

True or false: Hfr cells transfer genes to recipient cells in a particular order.

true

True or false: In prokaryotes, translation of an mRNA molecule can begin before transcription of the mRNA molecule is completed.

true

True or false: Induction and repression control the amount of enzymes but not their activity.

true

True or false: Mutations can either be beneficial, harmful, or have no impact on cells.

true

Auxotrophs

will not grow on a plate that lacks the growth factor, but will grow on a complete medium that contains the growth factor