PCB 3063 EXAM 4 QUESTIONS & ANSWERS
list the levels of control of gene activity in eukaryotes - Answers :1. chromatin
structure/DNA modifications
2. transcription regulation
3. processing of RNA transcripts
4. regulation of RNA stability
5 regulation of translation
6. post translationl modifications
Which gene control mechanisms from the previous question are not used in
prokaryotes, and why? - Answers :chromatin structure - do not package the same way,
RNA transcripts - don't splice introns or add a 5′ cap or poly(A) tail to their mRNA, RNA
stability - transcripts not as long lived
What are four things that influence the stability of eukaryotic mRNAs? - Answers :(1) the
5′ cap
(2) the coding sequence
(3) the 3′ UTR
(4) the poly(A) tail
List at least two ways that regulation of genes for yeast galactose- metabolizing
enzymes is different from regulation of E. coli lactose-utilizing enzymes. - Answers :1)
Yeast genes are not in an operon
(2) The yeast GAL genes are mainly controlled by a transcriptional activator; E. coli
genes are mainly controlled by a transcriptional repressor.
(3) The yeast GAL genes are under positive inducible control; the E. coli genes are
under negative inducible control.
(4) Yeast are eukaryotic, so regulation of any genes, including galactose- utilizing
enzymes, could include changes in chromatin structure, posttranscriptional modification
of RNA, and RNA stability.
What do you expect would develop if you injected Dnmt3 siRNA into honeybee larvae? -
Answers :female queen
How does histone acetylation affect chromatin structure? - Answers :Neutralizes
positive histone charges and binds to DNA more loosely
What effect does histone acetylation have on transcription? - Answers :Measurably
increase expression
Which of the following is an example of "crosstalk" in epigenetics?
a. DNA methylation leads to histone deacetylation.
b. DNA methylation leads to histone acetylation.
c. H2B ubiquitylation leads to H3K79 methylation.
, d. a and c
e. b and c - Answers :d. a and c
What histone modifications are associated with DNA repair?
a. H3K27 acetylation
b. H3K79 methylation
c. H2B ubiquitylation
d. a and c
e. b and c - Answers :e. b and c
What effect would the deamination of 5-methylcytosine in a promoter have on the
expression of that gene? - Answers :The gene will have increased expression because
this chemical reaction will result in thymine.
You are a researcher trying to understand the epigenetic mechanisms of queen bee
development. Which of the following experimental manipulations would probably not
lead to the development of a queen bee?
a. Feeding royal jelly to a female honeybee larva
b. Feeding decitabine, a DNA methyltransferase inhibitor, to a female larva
c. Injecting Dnmt3 siRNA into a female honeybee larva
d. Activation of a DNA cytosine deaminase enzyme in a female larva
e. Feeding royal jelly to an adult worker honeybee. - Answers :e. Feeding royal jelly to
an adult worker honeybee.
The promoter of gene A has histones that are acetylated on lysine 27 of histone H3, and
the promoter of gene B has histones that are methylated on lysine 4 of histone H3.
Which gene is being actively transcribed? - Answers :Both genes are actively
transcribed because both of those marks are associated with gene expression.
Which of the following is NOT a defining feature of paramutation?
a. The expression pattern is transmitted to future generations.
b. The altered allele is able to convert other alleles.
c. No DNA sequence differences between alleles.
d. Mutation of coding sequences generates new alleles.
e. These are all defining features of paramutation. - Answers :d. Mutation of coding
sequences generates new alleles.
How is the epigenetic trait induced by vinclozolin transmitted to offspring? - Answers
:DNA methylation is increased in sperm of treated males, and this methylation pattern is
inherited by offspring.
How will the result of strand slippage on the newly synthesized strand differ from the
result of strand slippage on the template strand? - Answers :Slippage on the newly
synthesized strand will result in an insertion, whereas slippage on the template strand
will result in a deletion.
list the levels of control of gene activity in eukaryotes - Answers :1. chromatin
structure/DNA modifications
2. transcription regulation
3. processing of RNA transcripts
4. regulation of RNA stability
5 regulation of translation
6. post translationl modifications
Which gene control mechanisms from the previous question are not used in
prokaryotes, and why? - Answers :chromatin structure - do not package the same way,
RNA transcripts - don't splice introns or add a 5′ cap or poly(A) tail to their mRNA, RNA
stability - transcripts not as long lived
What are four things that influence the stability of eukaryotic mRNAs? - Answers :(1) the
5′ cap
(2) the coding sequence
(3) the 3′ UTR
(4) the poly(A) tail
List at least two ways that regulation of genes for yeast galactose- metabolizing
enzymes is different from regulation of E. coli lactose-utilizing enzymes. - Answers :1)
Yeast genes are not in an operon
(2) The yeast GAL genes are mainly controlled by a transcriptional activator; E. coli
genes are mainly controlled by a transcriptional repressor.
(3) The yeast GAL genes are under positive inducible control; the E. coli genes are
under negative inducible control.
(4) Yeast are eukaryotic, so regulation of any genes, including galactose- utilizing
enzymes, could include changes in chromatin structure, posttranscriptional modification
of RNA, and RNA stability.
What do you expect would develop if you injected Dnmt3 siRNA into honeybee larvae? -
Answers :female queen
How does histone acetylation affect chromatin structure? - Answers :Neutralizes
positive histone charges and binds to DNA more loosely
What effect does histone acetylation have on transcription? - Answers :Measurably
increase expression
Which of the following is an example of "crosstalk" in epigenetics?
a. DNA methylation leads to histone deacetylation.
b. DNA methylation leads to histone acetylation.
c. H2B ubiquitylation leads to H3K79 methylation.
, d. a and c
e. b and c - Answers :d. a and c
What histone modifications are associated with DNA repair?
a. H3K27 acetylation
b. H3K79 methylation
c. H2B ubiquitylation
d. a and c
e. b and c - Answers :e. b and c
What effect would the deamination of 5-methylcytosine in a promoter have on the
expression of that gene? - Answers :The gene will have increased expression because
this chemical reaction will result in thymine.
You are a researcher trying to understand the epigenetic mechanisms of queen bee
development. Which of the following experimental manipulations would probably not
lead to the development of a queen bee?
a. Feeding royal jelly to a female honeybee larva
b. Feeding decitabine, a DNA methyltransferase inhibitor, to a female larva
c. Injecting Dnmt3 siRNA into a female honeybee larva
d. Activation of a DNA cytosine deaminase enzyme in a female larva
e. Feeding royal jelly to an adult worker honeybee. - Answers :e. Feeding royal jelly to
an adult worker honeybee.
The promoter of gene A has histones that are acetylated on lysine 27 of histone H3, and
the promoter of gene B has histones that are methylated on lysine 4 of histone H3.
Which gene is being actively transcribed? - Answers :Both genes are actively
transcribed because both of those marks are associated with gene expression.
Which of the following is NOT a defining feature of paramutation?
a. The expression pattern is transmitted to future generations.
b. The altered allele is able to convert other alleles.
c. No DNA sequence differences between alleles.
d. Mutation of coding sequences generates new alleles.
e. These are all defining features of paramutation. - Answers :d. Mutation of coding
sequences generates new alleles.
How is the epigenetic trait induced by vinclozolin transmitted to offspring? - Answers
:DNA methylation is increased in sperm of treated males, and this methylation pattern is
inherited by offspring.
How will the result of strand slippage on the newly synthesized strand differ from the
result of strand slippage on the template strand? - Answers :Slippage on the newly
synthesized strand will result in an insertion, whereas slippage on the template strand
will result in a deletion.
