BIO 302 EXAM 4 STUDY GUIDE
Ablation of the anchor cell in wild-type CC. elegans results in a vulva-less phenotype.
What phenotype(s) is to be expected if the anchor cell is ablated in a let-23 loss-of-
function mutant?
What about if the anchor cell is ablated in a let-23 gain-of-function mutant? - Correct
Answers -vulva-less
multi-vulvate
Suppose a mutation induces expression of the B-class gene in all four floral whorls.
Assuming A-class and C-class genes are expressed normally, what is the expected
structure of the flower from the outside to the inside? - Correct Answers -Petal-petal-
stamen-stamen
A complementation test is done to corroborate whether - Correct Answers -Two mutant
organisms have their mutations in the same gene
During vulva development in C. elegans, which cell fate pattern will the six VPCs display
in lag-2 loss-of-function mutants? - Correct Answers -331113
What is the developmental fate of the six vulval precursor cells in the absence of an
inductive signal from the anchor cell in C. elegans? - Correct Answers -They all
differentiate into hypodermis cells.
During a genetic screen, what needs to be done first? - Correct Answers -Induce
mutagenesis with EMS
During a genetic screen on a diploid organism, a recessive mutation can only be
identified in the F2 or F3 generations. (T/F) - Correct Answers -True
An Arabidopsis mutant whose whorls 1 and 2 give rise to sepals and whorls 3 and 4
give rise to carpels is what class of mutant according to the ABC model of flower
development: - Correct Answers -B-class mutant
A researcher wants to mutagenize an organism. She is not in need of a large number of
mutants but is more concerned with being able to find and then to amplify the mutated
sequence. Which of the following would therefore be more useful? - Correct Answers -
transposon insertion
,EMS (ethylmethane sulfonate) is mutagenic because ________. - Correct Answers -it
adds alkyl groups to bases
Cell signaling during much of C. elegans development occurs along concentration
gradients. What kind of signaling does this represent? - Correct Answers -induction
A homeotic mutant flower has an arrangement (from outside in) of carpels, stamens,
stamens, carpels instead of the usual sepal, petals, stamens, carpels. In general, Class
A genes specify sepals, Class A and B genes specify petals, Class B and C genes
specify stamens, and Class C specifies carpels. This mutant must therefore have a
mutation in - Correct Answers -a Class A gene.
Before Muller's discovery that radiation induces mutation, scientists had to work on
spontaneous mutants that were found solely by phenotype differences in natural
populations. Which of the features of Drosophila made it a fortuitous choice for Morgan
and his colleagues? - Correct Answers -large number of visible phenotypes
A mutagenesis screen provides 24 alleles shown by complementation analysis to be in
the same gene, which of the following is true? - Correct Answers -These mutants can
be used to identify the function of this gene.
How would you design a genetic screen to find genes involved in meiosis? - Correct
Answers -Genes involved in meiosis can be found by screening diploid yeast mutants
that are unable to produce viable ascospores on the sporulation medium.
Suppose we were successful in identifying 12 mutants using a screen for identifying
conditional mutants of S. cerevisiae in which the secretory system was defective.
Describe the crosses you would perform to determine the number of different genes
represented by the 12 mutations. - Correct Answers -Each mutant would be mated to
"wild type" and to every other "mutant" to create diploid strains. The diploids would be
assayed for growth at permissive and restrictive temperature. Diploids formed by mating
a mutant to a "wild type" that can grow at "restrictive" temperatures identify the mutation
as "recessive." Only "recessive" mutations can be studied using complementation
analysis. Diploids formed by mating two "recessive" mutants identify mutations in the
same gene if the diploid cannot grow at "restrictive" temperature (non-
complementation), and they identify mutations in different genes if the diploids can grow
at "restrictive" temperature (complementation).
Based on your knowledge of the genetic tools for studying baker's yeast, how would you
clone the genes that are mutated in your respective yeast strains? - Correct Answers -
complementation of the temperature-sensitive lethal phenotype
What are the approaches to cloning the human orthologs of the yeast genes? - Correct
Answers -This could be done by using the yeast genes as a probe to screen a human
cDNA library.
, This could be done by using the sequence of yeast genes to create primers to amplify
the human genes by PCR.
Age is the greatest of all risk factors for cancer because ________. - Correct Answers -
somatic mutations accumulate with age
Most cancers are caused by ________ mutations whereas a minority of cancers is
caused by ________ mutations. - Correct Answers -somatic; germline
Inflammation can aide tumor growth by promoting which of the following? - Correct
Answers -angiogenesis
What do cancer cells not do when they are irregular? - Correct Answers -apoptosis
Cells whose normal function involves preventing cell division are generally
characterized as ________. - Correct Answers -tumor suppressor genes
A proto-oncogene has what characteristics? - Correct Answers -a gene that promotes
cell division and, when mutated, leads to cancer progression
In their normal state, what is the primary function of the protein products of the BRCA1
and BRCA2 genes? - Correct Answers -They detect and repair DNA damage.
Cancer susceptibility can run in families due to ________. - Correct Answers -germline
mutation
TP53 protein - Correct Answers -Stimulating DNA damage repair
Initiating apoptosis
Pausing the cell cycle
What is the function of restriction endonucleases in bacteria? - Correct Answers -They
provide a defense mechanism against infection by viruses.
Restriction endonucleases cut DNA at specific recognition sequences and then bond
two strands covalently with the same "sticky ends." (T/F) - Correct Answers -False
BamHI cuts the sequence 5′ G|GATCC 3′. Which of the following sequences would not
be recognized by this enzyme? - Correct Answers -3′ TCTTAAG 5′
DNA Sequencing Primer Site - Correct Answers -allows for identification of the DNA
segment cloned into the plasmid
Multiple cloning site - Correct Answers -region where pieces of DNA are cloned into the
plasmid
Ablation of the anchor cell in wild-type CC. elegans results in a vulva-less phenotype.
What phenotype(s) is to be expected if the anchor cell is ablated in a let-23 loss-of-
function mutant?
What about if the anchor cell is ablated in a let-23 gain-of-function mutant? - Correct
Answers -vulva-less
multi-vulvate
Suppose a mutation induces expression of the B-class gene in all four floral whorls.
Assuming A-class and C-class genes are expressed normally, what is the expected
structure of the flower from the outside to the inside? - Correct Answers -Petal-petal-
stamen-stamen
A complementation test is done to corroborate whether - Correct Answers -Two mutant
organisms have their mutations in the same gene
During vulva development in C. elegans, which cell fate pattern will the six VPCs display
in lag-2 loss-of-function mutants? - Correct Answers -331113
What is the developmental fate of the six vulval precursor cells in the absence of an
inductive signal from the anchor cell in C. elegans? - Correct Answers -They all
differentiate into hypodermis cells.
During a genetic screen, what needs to be done first? - Correct Answers -Induce
mutagenesis with EMS
During a genetic screen on a diploid organism, a recessive mutation can only be
identified in the F2 or F3 generations. (T/F) - Correct Answers -True
An Arabidopsis mutant whose whorls 1 and 2 give rise to sepals and whorls 3 and 4
give rise to carpels is what class of mutant according to the ABC model of flower
development: - Correct Answers -B-class mutant
A researcher wants to mutagenize an organism. She is not in need of a large number of
mutants but is more concerned with being able to find and then to amplify the mutated
sequence. Which of the following would therefore be more useful? - Correct Answers -
transposon insertion
,EMS (ethylmethane sulfonate) is mutagenic because ________. - Correct Answers -it
adds alkyl groups to bases
Cell signaling during much of C. elegans development occurs along concentration
gradients. What kind of signaling does this represent? - Correct Answers -induction
A homeotic mutant flower has an arrangement (from outside in) of carpels, stamens,
stamens, carpels instead of the usual sepal, petals, stamens, carpels. In general, Class
A genes specify sepals, Class A and B genes specify petals, Class B and C genes
specify stamens, and Class C specifies carpels. This mutant must therefore have a
mutation in - Correct Answers -a Class A gene.
Before Muller's discovery that radiation induces mutation, scientists had to work on
spontaneous mutants that were found solely by phenotype differences in natural
populations. Which of the features of Drosophila made it a fortuitous choice for Morgan
and his colleagues? - Correct Answers -large number of visible phenotypes
A mutagenesis screen provides 24 alleles shown by complementation analysis to be in
the same gene, which of the following is true? - Correct Answers -These mutants can
be used to identify the function of this gene.
How would you design a genetic screen to find genes involved in meiosis? - Correct
Answers -Genes involved in meiosis can be found by screening diploid yeast mutants
that are unable to produce viable ascospores on the sporulation medium.
Suppose we were successful in identifying 12 mutants using a screen for identifying
conditional mutants of S. cerevisiae in which the secretory system was defective.
Describe the crosses you would perform to determine the number of different genes
represented by the 12 mutations. - Correct Answers -Each mutant would be mated to
"wild type" and to every other "mutant" to create diploid strains. The diploids would be
assayed for growth at permissive and restrictive temperature. Diploids formed by mating
a mutant to a "wild type" that can grow at "restrictive" temperatures identify the mutation
as "recessive." Only "recessive" mutations can be studied using complementation
analysis. Diploids formed by mating two "recessive" mutants identify mutations in the
same gene if the diploid cannot grow at "restrictive" temperature (non-
complementation), and they identify mutations in different genes if the diploids can grow
at "restrictive" temperature (complementation).
Based on your knowledge of the genetic tools for studying baker's yeast, how would you
clone the genes that are mutated in your respective yeast strains? - Correct Answers -
complementation of the temperature-sensitive lethal phenotype
What are the approaches to cloning the human orthologs of the yeast genes? - Correct
Answers -This could be done by using the yeast genes as a probe to screen a human
cDNA library.
, This could be done by using the sequence of yeast genes to create primers to amplify
the human genes by PCR.
Age is the greatest of all risk factors for cancer because ________. - Correct Answers -
somatic mutations accumulate with age
Most cancers are caused by ________ mutations whereas a minority of cancers is
caused by ________ mutations. - Correct Answers -somatic; germline
Inflammation can aide tumor growth by promoting which of the following? - Correct
Answers -angiogenesis
What do cancer cells not do when they are irregular? - Correct Answers -apoptosis
Cells whose normal function involves preventing cell division are generally
characterized as ________. - Correct Answers -tumor suppressor genes
A proto-oncogene has what characteristics? - Correct Answers -a gene that promotes
cell division and, when mutated, leads to cancer progression
In their normal state, what is the primary function of the protein products of the BRCA1
and BRCA2 genes? - Correct Answers -They detect and repair DNA damage.
Cancer susceptibility can run in families due to ________. - Correct Answers -germline
mutation
TP53 protein - Correct Answers -Stimulating DNA damage repair
Initiating apoptosis
Pausing the cell cycle
What is the function of restriction endonucleases in bacteria? - Correct Answers -They
provide a defense mechanism against infection by viruses.
Restriction endonucleases cut DNA at specific recognition sequences and then bond
two strands covalently with the same "sticky ends." (T/F) - Correct Answers -False
BamHI cuts the sequence 5′ G|GATCC 3′. Which of the following sequences would not
be recognized by this enzyme? - Correct Answers -3′ TCTTAAG 5′
DNA Sequencing Primer Site - Correct Answers -allows for identification of the DNA
segment cloned into the plasmid
Multiple cloning site - Correct Answers -region where pieces of DNA are cloned into the
plasmid
