BIO 3001 EXAM 2 QUESTIONS &
ANSWERS(GRADED A+)
Regulation of Gene Expression - ANSWERPromoter: site where RNA polymerase
can bind to DNA and begin transcription.
Operator: on/off switch
Genes are coordinately controlled
Operon: the operator, the promoter, and the genes they control
Lederberg and Tatum (1945) experiments in bacteria that could not make arginine or
tryptophan but exchanged genetic information and recovered functions; bacterial
transformation - ANSWERSexual reproduction (conjugation) between bacteria
resulting in transformation and the ability to now produce colonies. Shows that there
is genetic exchange between bacteria
2 E. coli mutants:
One can't synthesize tryptophan [can make argenine]
One can't synthesize argenine [can make tryptophan]
Exchange genetic information -- Bacterial Transformation: naturally exchange DNA
E. Coli Mutation Rate - ANSWERThe probability of a spontaneous mutation
occurring in a given E. coli gene averages only about one in ten million (1x10^-7) per
cell division. But among the 2x10^10 new E. coli cells that arise each day in a
person's intestine, there will be approximately (2x10^10) x (1x10^-7) = 2,000 bacteria
that have a mutation in that gene. The total number of mutations when all 4,300 E.
coli genes are considered is about 4,300 x 2,000 = 9 million per day per human host.
The key point is that new mutations, though rare, can increase genetic diversity
quickly in species with short generation times and large populations. This diversity, in
turn, can lead to rapid evolution: individuals that are genetically better equipped for
their environment tend to survive and reproduce more prolifically than less fit
individuals.
R or resistance plasmids - ANSWER"Resistance genes"
Carry the genes to code for enzymes that specifically destroy or otherwise hinder the
effectiveness of certain antibiotics, such as tetracycline or ampicillin.
Exposing a bacterial population to a specific antibiotic, whether in a laboratory
culture or within a host organism, will kill antibiotic-sensitive bacteria but not those
that happen to have r plasmids with genes that counter the antibiotic. Under these
circumstances, we could predict that natural selection would cause the fraction of the
bacterial population carrying genes for antibiotic resistance to increase, and that is
exactly what happens.
F plasmid and bacterial conjugation through pilus - ANSWERConjugation: DNA is
transferred between two prokaryotic cells (usually of the same species) that are
temporarily joined.
In bacteria, the DNA transfer is always one-way: one cell donates the DNA, and the
other receives it.
, In E. coli, a pilus of the donor cell attaches to the recipient. The pilus then retracts,
pulling the two E. coli cells together , much like a grappling hook. The next step is
thought to be the formation of a temporary "mating bridge" between the two cells,
through which the donor may transfer the recipient.
F Factor: a particular piece of DNA that gives the ability to form pili and donate DNA
during conjugation. The F factor of E. coli consists of about 25 genes, most required
for the production of pili.
The F factor can exist either as a plasmid or as a segment of DNA within the
bacterial chromosome.
F Plasmid: the F factor in its plasmid form.
Cells containing the F plasmid, designated F+ cells, function as DNA donors during
conjugation. Cells lacking the F factor, designated F-, function as DNA recipients
during conjugation. The F+ condition is transferrable in the sense that an F+ cell
converts an F- cell to F+ if a copy of the entire F+ plasmid is transferred.
Conjugation: DNA is transferred between two prokaryotic cells (usually of the same
species) that are temporarily joined.
In bacteria, the DNA transfer is always one-way: one cell donates the DNA, and the
other receives it.
In E. coli, a pilus of the donor cell attaches to the recipient. The pilus then retracts,
pulling the two E. coli cells together , much like a grappling hook. The next step is
thought to be the formation of a temporary "mating bridge" between the two cells,
through which the donor may transfer the recipient.
F Factor: a particular piece of DNA that gives the ability to form pili and donate DNA
during conjugation
Restriction endonucleases (Werner Arber & Daisy Dussoix 1961) - ANSWERWhy
does bacteriophage lamda grow well in one strain of bacteria and not in another?
They discovered restriction enzymes - identify a target sequence of nucleotide in the
DNA and make a cut right there.
Using restriction enzymes for more:
Cutting up human DNA?
Restriction enzymes cut sugar-phosphate backbones
DNA fragments added from another molecule cut by same enzyme.
Replica plating: spread bacteria on nutrient agar
Key to making copies of original plate
Test: using plasmid so we can FIND which bacteria got the insertion of human DNA.
Wollman and Jacob (1957) mapping the sequence of bacterial genes with
interrupted conjugation - ANSWERUsed interrupted mating technique: the
chromosome of Hfr bacteria were transferred linearly -> gene order and distance can
be predicted b/c specific genes were transferred/recombined sooner than others.
BUT order of genes transferred varied between Hfr strains -> origin of transfer is diff
per Hrf strain
Jacob and Monod (1961) bacterial operon - ANSWERUsed interrupted mating
technique and identified clusters of related genes with adjacent promoter region and
switch segment, the operator.
Named this the bacterial operon.
ANSWERS(GRADED A+)
Regulation of Gene Expression - ANSWERPromoter: site where RNA polymerase
can bind to DNA and begin transcription.
Operator: on/off switch
Genes are coordinately controlled
Operon: the operator, the promoter, and the genes they control
Lederberg and Tatum (1945) experiments in bacteria that could not make arginine or
tryptophan but exchanged genetic information and recovered functions; bacterial
transformation - ANSWERSexual reproduction (conjugation) between bacteria
resulting in transformation and the ability to now produce colonies. Shows that there
is genetic exchange between bacteria
2 E. coli mutants:
One can't synthesize tryptophan [can make argenine]
One can't synthesize argenine [can make tryptophan]
Exchange genetic information -- Bacterial Transformation: naturally exchange DNA
E. Coli Mutation Rate - ANSWERThe probability of a spontaneous mutation
occurring in a given E. coli gene averages only about one in ten million (1x10^-7) per
cell division. But among the 2x10^10 new E. coli cells that arise each day in a
person's intestine, there will be approximately (2x10^10) x (1x10^-7) = 2,000 bacteria
that have a mutation in that gene. The total number of mutations when all 4,300 E.
coli genes are considered is about 4,300 x 2,000 = 9 million per day per human host.
The key point is that new mutations, though rare, can increase genetic diversity
quickly in species with short generation times and large populations. This diversity, in
turn, can lead to rapid evolution: individuals that are genetically better equipped for
their environment tend to survive and reproduce more prolifically than less fit
individuals.
R or resistance plasmids - ANSWER"Resistance genes"
Carry the genes to code for enzymes that specifically destroy or otherwise hinder the
effectiveness of certain antibiotics, such as tetracycline or ampicillin.
Exposing a bacterial population to a specific antibiotic, whether in a laboratory
culture or within a host organism, will kill antibiotic-sensitive bacteria but not those
that happen to have r plasmids with genes that counter the antibiotic. Under these
circumstances, we could predict that natural selection would cause the fraction of the
bacterial population carrying genes for antibiotic resistance to increase, and that is
exactly what happens.
F plasmid and bacterial conjugation through pilus - ANSWERConjugation: DNA is
transferred between two prokaryotic cells (usually of the same species) that are
temporarily joined.
In bacteria, the DNA transfer is always one-way: one cell donates the DNA, and the
other receives it.
, In E. coli, a pilus of the donor cell attaches to the recipient. The pilus then retracts,
pulling the two E. coli cells together , much like a grappling hook. The next step is
thought to be the formation of a temporary "mating bridge" between the two cells,
through which the donor may transfer the recipient.
F Factor: a particular piece of DNA that gives the ability to form pili and donate DNA
during conjugation. The F factor of E. coli consists of about 25 genes, most required
for the production of pili.
The F factor can exist either as a plasmid or as a segment of DNA within the
bacterial chromosome.
F Plasmid: the F factor in its plasmid form.
Cells containing the F plasmid, designated F+ cells, function as DNA donors during
conjugation. Cells lacking the F factor, designated F-, function as DNA recipients
during conjugation. The F+ condition is transferrable in the sense that an F+ cell
converts an F- cell to F+ if a copy of the entire F+ plasmid is transferred.
Conjugation: DNA is transferred between two prokaryotic cells (usually of the same
species) that are temporarily joined.
In bacteria, the DNA transfer is always one-way: one cell donates the DNA, and the
other receives it.
In E. coli, a pilus of the donor cell attaches to the recipient. The pilus then retracts,
pulling the two E. coli cells together , much like a grappling hook. The next step is
thought to be the formation of a temporary "mating bridge" between the two cells,
through which the donor may transfer the recipient.
F Factor: a particular piece of DNA that gives the ability to form pili and donate DNA
during conjugation
Restriction endonucleases (Werner Arber & Daisy Dussoix 1961) - ANSWERWhy
does bacteriophage lamda grow well in one strain of bacteria and not in another?
They discovered restriction enzymes - identify a target sequence of nucleotide in the
DNA and make a cut right there.
Using restriction enzymes for more:
Cutting up human DNA?
Restriction enzymes cut sugar-phosphate backbones
DNA fragments added from another molecule cut by same enzyme.
Replica plating: spread bacteria on nutrient agar
Key to making copies of original plate
Test: using plasmid so we can FIND which bacteria got the insertion of human DNA.
Wollman and Jacob (1957) mapping the sequence of bacterial genes with
interrupted conjugation - ANSWERUsed interrupted mating technique: the
chromosome of Hfr bacteria were transferred linearly -> gene order and distance can
be predicted b/c specific genes were transferred/recombined sooner than others.
BUT order of genes transferred varied between Hfr strains -> origin of transfer is diff
per Hrf strain
Jacob and Monod (1961) bacterial operon - ANSWERUsed interrupted mating
technique and identified clusters of related genes with adjacent promoter region and
switch segment, the operator.
Named this the bacterial operon.
