Genetics 4
Rank the following configurations of mRNA from most (#1) to least (#4) protein produced. ____mRNA with a 5' cap only ____mRNA with BOTH a 5' cap and a poly(A) tail ____mRNA with NEITHER a 5' cap nor a poly(A) tail ____mRNA with a poly(A) tail only
2 1 4 3
In the absence of arabinose, an alternate sugar source for E. coli, the "C" protein binds to a promoter sequence and prevents the transcription of an operon encoding genes required for arabinose metabolism. This is an example of Question options: positive regulation negative regulation attenuation negative corepression transcriptional initiation
Negative regulation
When the trp repressor is bound to its operator sequence, transcription of the trp operon is
Off
When CAP binds to the CAP site, what happens? Transcription fo the lac operon is blocked. cAMP is released from the CAP protein. RNA polymerase is recruited to the promoter region. The lac repressor is blocked from binding the operator sequence.
RNA polymerase is recruited to the promoter region.
What is the signaling molecule produced by prokaryotic cells in the absence of glucose (the preferred sugar source)? tryptophan lactose cAMP allolactose
cAMP
Tryptophan bind to the Trp repressor, and acts as a inducer repressor activator co-repressor
co-repressor
Consider a mutation in the DNA sequence that introduces a nonsense mutation midway through the lacZ gene. What effect will that have on the transcription of the operon in the presence of high lactose and low glucose? -expression of the lac operon will no longer be inducible by lactose, and will be constitutively expressed. -transcription will be terminated midway through the lacZ gene. -the lac operon will be highly expressed (turned on). -the lac operon will be highly repressed (turned off).
the lac operon will be highly repressed (turned off).
When there are low levels of tryptophan, -the ribosome increases translation speed in order to increase the synthesis of the genes that synthesize tryptophan. -the ribosome prevents transcription of the trp operon. -the ribosome is unable to initiate translation on the mRNA containing the tryptophan biosynthesis genes. -the ribosome stalls when translating the trpL peptide because there are no charged tRNAs to complete the leader peptide sequence.
the ribosome stalls when translating the trpL peptide because there are no charged tRNAs to complete the leader peptide sequence.
What would be the expectation following a mutation in a DNA methylase that inhibited methylation? transcription of epigenetically regulated genes would be increased. transcription of epigenetically regulated genes would be decreased.
transcription of epigenetically regulated genes would be increased.
When tryptophan levels are low, a stem loop structure forms between which two complementary regions of the trpL mRNA?
2 and 3
When tryptophan levels are high, a stem loop structure forms between which two complementary regions of the trpL mRNA?
3 and 4
How many complementary regions that can form stem-loop structures are found on the mRNA encoding the trpL peptide? one two three four
4
CpG is shorthand for
5'=Cytosine=phosphate-Guanine-3'
How do the 5'-CAP and the 3'-polyA tail of an eukaryotic mRNA influence it's translation (refer to Fig2)? -If the polyA-tail is long, and the 5'CAP is absent, translation is increased. -If the polyA tail is short, translation is increased. -If the 5'CAP is present, translation is inhibited. -A long polyA-tail and a 5'-CAP leads to the highest levels of translation.
A long polyA-tail and a 5'-CAP leads to the highest levels of translation.
Cytoplasmic poly(A)-binding protein (PABC) binds poly(A) tails to terminate translation trigger mRNA degradation promote translation all of the above
All of the above
Which of the following sequences contains a CpG site? Question options: 5'-ATCGTCCGG-3' 5' ATCAGCTACGC-3' all of the above none of the above
All of the above
A woman is heterozygous for a paternally imprinted gene (A1A2). During gametogenesis, she will imprint gametes that inherit the A1 allele and gametes that inherit the A2 allele. T.F
False
A woman is heterozygous for a paternally imprinted gene (A1A2). During gametogenesis, she will imprint gametes that inherit the A1 allele and gametes that inherit the A2 allele. T/F
False
Epigenetic changes alter gene expression, resulting in permanent changes (mutations) to the genome. T/F
False
Nutriceuticals that reduce DNA methylation are a great way to offset the impact of environmental perturbations to our epigenome. T.F
False
When trptophan levels are high, gene expression of the trp operon is upregulated.
False
A woman is heterozygous for a maternally imprinted gene (A1A2). During gametogenesis, she will imprint gametes that inherit the A1 allele and gametes that inherit the A2 allele. T/F
True
Genomic imprinting is an epigenetic phenomenon that Question options: -causes genes to be expressed or not depending on whether they are inherited from the mother or the father. -explains how transcription is inactivated by histone modifications. -is characterized by a rapid learning process that takes place early in the life of a social animal, and explains why baby geese will follow the first animal they meet (be is a goose or a human). -results in expression of a gene in females only.
causes genes to be expressed or not depending on whether they are inherited from the mother or the father.
Which of the following are considered primary mechanisms for epigenetic modifications? (choose all that apply) transcription factors histone tail modification DNA methylation poly(A) tail structures ncRNA expression
histone tail modification DNA methylation ncRNA expression
Select all of the following that are examples of programmed epigenetics imprinting cell differentiation x-linked inheritance x-inactivation
imprinting cell differentiation x-inactivation
In the lac operon, which of the following is constitutively expressed? lacI (encoding the lac repressor) lacA lacZ (encoding B-galactosidase) lacY (encoding the lac permease)
lacI (encoding the lac repressor)
Expression of the lac operon is lowest when -lactose is present but glucose is not. -lactose is absent but glucose is present. -lactose and glucose are present. -neither lactose nor glucose are present.
lactose is absent but glucose is present.
A CpG island is a stretch of DNA rich in CpGs with sets of 6 CpGs interrupted by short poly A regions with sets of 6 CpGs interrupted by short AT regions with only CpGs
rich in CpGs
Select all of the following that are examples of environmental factors that can affect the epigenome. Question options: stress exposure to toxins x-inactivation maternal care diet
stress exposure to toxins maternal care diet
CpGs are targets of RNA polymerase initiation factors transcription factors targets for methylation of DNA targets for acetylation of DNA
targets for methylation of DNA
Negative regulation refers to -the binding of a repressor protein to a specific DNA sequence thus activating transcription. -the binding of an inducer to a specific DNA sequence thus preventing transcription. -the binding of an inducer to a specific DNA sequence thus activating transcription. -the binding of a repressor protein to a specific DNA sequence thus preventing transcription.
the binding of a repressor protein to a specific DNA sequence thus preventing transcription.
Imprinted genes are (select all that apply) transcriptionally silenced methylated during reproduction of somatic cells methylated during gametogenesis transcriptionally active unmethylated
transcriptionally silenced methylated during gametogenesis
When a short, non-coding sequence of RNA binds to a complementary sequence in an mRNA, it will Question options: -promote the formation of a stem loop structure which will cause termination of translation -target the now double-stranded mRNA for degradation which will stop further translation -promote ribosomal binding which will initiate translation -block binding of initiation factors that help the ribosome find the ribosomal binding site which will block translation
-target the now double-stranded mRNA for degradation which will stop further translation
Enzymes that add -CH3 (methyl) groups to cytosine residues on a DNA chain are called DNA methyltransferases DNA cytomethylases DNA demethylases DNA methlycytoases
DNA methyltransferases
If you examined the methylation patterns on DNA in eggs and sperm of the same species you would expect them to be different the same
Different
A man is heterozygous for a maternally imprinted gene (A1A2). During gametogenesis, he will imprint gametes that inherit the A1 allele and gametes that inherit the A2 allele. T/F
False
When the mRNA encoding the trpL peptide forms a stem-loop structure in regions 2 and 3 (called the antitermination structure), this acts as a transcription termination sequence for RNA polymerase. T/F
False
Tryptophan is the final product of the enzymes encoded by the Trp operon. Consider how tryptophan is involved in the regulation of the Trp operon. Is this an example of a positive or negative feedback loop?
Negative feedback loop
A segment of mRNA that forms under certain temperatures and regulated translation is called a thermosensor. Thermosensors are considered to be Splicing factors siRNAs Ribozyme Riboswitch
Riboswitch
In the lac operon, -allolactose acts as an inducer while cAMP acts as an inhibitor. -allolactose and cAMP are both regulatory proteins. -both allolactose and cAMP are inducer molecules. -allolactose acts an an inhibitor while cAMP acts as an inducer molecule.
both allolactose and cAMP are inducer molecules.
A woman is an unaffected carrier for a gene that is maternally imprinted. Which of the following is true? Question options: -The daughters that receive the disease allele will be affected while sons that receive the disease allele will be unaffected. -Her children will be unaffected, but the carrier daughters will have affected children. -Half of her children will be affected, and the affected daughters will have affected children but the affected sons will have carrier children. -Sons that receive the disease allele will be affected while daughters that receive the disease allele will be unaffected. -Her children will be unaffected, but the carrier sons will have affected children.
-Her children will be unaffected, but the carrier sons will have affected children.
In the trp operon, a small peptide (called the leader peptide) is produced by the trpL gene. -The DNA containing the trpL gene can form a secondary structure that halts transcription. -The mRNA containing the trpL gene can form a secondary structures that halts transcription. -The mRNA containing the trpL gene can form a secondary structure that recruits RNA polymerase. -The mRNA containing the trpL gene contains a recognition sequence where the trp repressor can bind. Question 6
The mRNA containing the trpL gene can form a secondary structures that halts transcription.
Which of the following is true? The operator sequence is where CAP binds to the DNA. The operator sequence is upstream of lacZ and downstream of lacZ's promoter. The operator sequence is downstream of lacZ and upstream of lacZ's promoter. The operator sequence is upstream of the CAP binding site.
The operator sequence is upstream of lacZ and downstream of lacZ's promoter.
When tryptophan levels are high, which of the following is most likely to occur. 1. The ribosome is stalled at two tryptophan codons on the mRNA encoding the trpL peptide. The stalled ribosome allows the formation of a stem loop structure within the mRNA known as the anti-termination structure. RNA polymerase is allowed to continute, transcribing the typtophan biogenesis genes. 2. The ribosome is stalled at two tryptophan codons on the mRNA encoding the trpL peptide. The stalled ribosome blocks two of the 4 complementary regions within the trpL message, allowing the formation of the attenuation structure between the last two complementary regions. This structure acts as a rho-independent transcription termination sequence that prevents the transcription of the tryptophan biogenesis genes. 3. The ribosome is able to incorporate tryptophan into the trpL peptide. As the ribosome proceeds down the mRNA, it blocks two of the 4 complementary regions within the trpL message. A stem-loop structure, known as the anti-termination structure, forms between the last two complementary regions. RNA polymerase is allowed to continute, transcribing the typtophan biogenesis genes. 4. The ribosome is able to incorporate tryptophan into the trpL peptide. As the ribosome proceeds down the mRNA, it blocks two of the 4 complementary regions within the trpL message. A stem-loop structure, known as the attenuation structure, forms between the last two complementary regions, acting as a rho-independent transcription termination sequence that prevents the transcription of the tryptophan biogenesis genes.
The ribosome is able to incorporate tryptophan into the trpL peptide. As the ribosome proceeds down the mRNA, it blocks two of the 4 complementary regions within the trpL message. A stem-loop structure, known as the attenuation structure, forms between the last two complementary regions, acting as a rho-independent transcription termination sequence that prevents the transcription of the tryptophan biogenesis genes.
Why is gene expression typically regulated at the transcriptional level in prokaryotes? -In prokaryotes, genes are found in operons, and therefore must be transcriptionally regulated. -It takes multiple transcripts to produce a single protein, so it is energetically favorable to prevent transcription. -Translation occurs as a transcript is being synthesized; therefore controlling transcription has a large effect than controlling translation. -Transcription is a simpler process than translation, and therefore it is easier to control.
Translation occurs as a transcript is being synthesized; therefore controlling transcription has a large effect than controlling translation.
Attenuation refers to the control of gene expression through the premature termination of transcription.
True
Based on the paper that you read, poly(A) tails on mRNA not only play a role in terminating transcription, they play a complicated role in regulating gene expression.
True
CpGs are often found around promotor regions for genes. T/F
True
Different tissues can have different imprinting patterns. TrueFalse
True
When tryptophan levels are low, which of the following is most likely to occur? 1. Uncharged tRNA cause the ribosome to stall during synthesis of the trlL peptide, allowing for the formation of the attenuation structure on the mRNA that promotes transcription of the tryptophan biosynthesis genes. 2. Uncharged tRNA cause the ribosome to stall during synthesis of the trlL peptide, allowing for the formation of the attenuation structure on the mRNA that acts as a transcription termination sequence that prevents the transcription of the tryptophan biosynthesis genes. 3. Uncharged tRNA cause the ribosome to stall during synthesis of the trlL peptide, allowing for the formation of the anti-termination (anti-attenuation) structure on the mRNA that acts as a transcription termination sequence that prevents the transcription of the tryptophan biosynthesis genes. 4. Uncharged tRNA cause the ribosome to stall during synthesis of the trlL peptide, allowing for the formation of the anti-termination (anti-attenuation) structure on the mRNA that promotes transcription of the tryptophan biosynthesis genes.
Uncharged tRNA cause the ribosome to stall during synthesis of the trlL peptide, allowing for the formation of the anti-termination (anti-attenuation) structure on the mRNA that promotes transcription of the tryptophan biosynthesis genes.
Which of the following terms or descriptions apply to CAP? Select all that apply. activator protein repressor protein positive regulator negative regulator regulatory sequence inducer molecule enzyme that metabolizes lactose signaling molecule
activator protein; positive regulator
Eukaryotes regulate gene expression in which of the following? -chromatin remodeling -transcription -splicing of introns to produce the mature mRNA -export of mRNA from the nucleus to the cytosol -translation -degradation of RNAs -post-translational modifications of proteins
all of the above
Consider an E.coli cell that has a mutation in the operator sequence of the lac operon that prevents the lac repressor from binding. Would you expect the lac operon to be inducible, repressed, or constitutively expressed? repressed constitutively expressed inducible by lactose inducible by glucose
constitutively expressed
Genes with constitutive expression are -regulated such that expression occurs through activation of a promoter sequence -regulated such that expression occurs through repression of a promoter sequence -unregulated so that it is not possible to predict the amount of the gene that is expressed at any given moment -expressed at constant levels
expressed at constant levels
Consider a trait caused by a particular variant of a maternally imprinted gene. An unaffected woman is heterozygous for the disease allele. Her partner is homozygous for the wild type, non-disease, allele. You expect that (select all that apply) -none of their offspring will be unaffected carriers of the disease allele -half of their offspring will be unaffected carriers of the disease allele -all of their offspring will be unaffected carriers of the disease allele -none of their offspring will develop the disease -half of their offspring will develop the disease -all of their offspring will develop the disease
half of their offspring will be unaffected carriers of the disease allele None of their offspring will develop the disease
The rate of transcription of a particular gene is low to zero. Based on this you wouldn't be surprised to find highly acetylated CpG islands around the promotor region highly acetylated CpG islands around the promotor region highly methylated CpG islands around the promotor region highly unmethylated CpG islands around the promotor region
highly methylated CpG islands around the promotor region
Expression of the lac operon is highest when lactose is present but glucose is not. neither lactose nor glucose are present. lactose is absent but glucose is present. lactose and glucose are present.
lactose is present but glucose is not.
Select all of the following that are different between a skin cell and a liver cell. Question options: mRNA DNA proteins methylation patters of DNA
mRNA proteins methylation patters of DNA
Select all of the following that inhibit transcription methylation of histone tails methylation of DNA sequences acetylation of histone tails
methylation of histone tails methylation of DNA sequences
Regulation of the trp operon by the trp repressor is an example of Question options: attenuation corepression negative regulation positive regulation
negative regulation
When lactose is present, but glucose is not, the lac repressor is ______ to its regulatory sequence, and CAP is _______ to its regulatory sequence. bound, bound not bound, not bound not bound, bound bound, not bound
not bound, bound
When lactose and glucose are present, the lac repressor is ______ to its regulatory sequence, and CAP is _______ to its regulatory sequence, and transcription levels are ______. not bound, not bound, medium not bound, bound, off not bound, bound, high not bound, not bound, off not bound, not bound, high not bound, bound, medium
not bound, not bound, medium
Nuclear Poly(A)-binding protein (PABN) controls splicing 3' cleavage poly(A) tail addition 5' capping
poly(A) tail addition
CAP controls the expression of the lac operon through -positive regulation, as binding of CAP to the CAP site inhibits transcription. -positive regulation, as binding of CAP to the CAP site promotes transcription. -negative regulation, as binding of CAP to the CAP site inhibits transcription. -negative regulation, as binding of CAP to the CAP site promotes transcription.
positive regulation, as binding of CAP to the CAP site promotes transcription.
At which stage can gene regulation occur in eukaryotes, but not prokaryotes? Question options: -processing of pre-mRNA to mRNA during intron removal -post-translational modifications -translation -transcription
processing of pre-mRNA to mRNA during intron removal
When tryptophan levels are high, a stem loop structure in the leader peptide -promotes the formation of the attenuation structure that promotes transcription by RNA polymerase. -promotes the formation of the attenuation structure that acts a transcription termination sequence for RNA polymerase. -promotes the formation of the anti-termination structure that acts a transcription termination sequence for RNA polymerase. -promotes the formation of the anti-termination structure that promotes transcription by RNA polymerase.
promotes the formation of the attenuation structure that acts a transcription termination sequence for RNA polymerase.
Consider an E. coli cell that contains a mutation in the lac repressor that results in a protein that cannot bind allolactose. Would you expect the lac operon to be inducible, repressed, or constitutively expressed? inducible by glucose repressed inducible by lactose constitutively expressed
repressed
Which of the following is most accurate in describing the level of imprinting of mammalian genes. Question options: very few mammalian genes, ~1%, are imprinted about half of mammalian genes are imprinted more than half, but not all, ~70%, of mammalian genes are imprinted
very few mammalian genes, ~1%, are imprinted
A man is heterozygous for a paternally imprinted gene (A1A2). During gametogenesis, he will imprint gametes that inherit the A1 allele and gametes that inherit the A2 allele. T/F
True
A woman is heterozygous for a maternally imprinted gene (A1A2). During gametogenesis, she will imprint gametes that inherit the A1 allele and gametes that inherit the A2 allele. T.F
True
Epigenetics refers to changes in heritable changes in gene expression that do not alter the underlying DNA sequence. T/F
True
Imprinting does not alter Mendelian inheritance patterns of alleles. For example, if a person is heterozygous for an imprinted gene (A1A2), then 50% of their offspring will inherit the A1 allele and 50% of the offspring will inherit the A2 allele. T/F
True
Imprinting leads to monoallelic expression. T/f
True
In the trp operon, a small peptide (called the leader peptide) is produced by the trpL gene. The mRNA containing the trpL gene can form different secondary structures. T/F
True
Some mRNAs are translated at different rates than other mRNAs, leading to large variations in translation efficiency.
True
The impact of your grandparents lifestyle choices - diet or choice to smoke - can potentially be seen in your epigenome. T.F
True
The trp repressor is less efficient at blocking transcription than the lac repressor. T/F
True
When the mRNA encoding the trpL peptide forms a stem-loop structure in regions 3 and 4 (called the attenuation structure), this acts as a transcription termination sequence for RNA polymerase. T/F
True
You can inherit not only the DNA but also the methylation patterns of DNA from your parents. T/F
True
How many promoters are found at the lac operon? -one: one promoter controls expression of lacZ, lacY and lacA -0: no promoters are involved in the lac operon -four: lacZ, lacY, lacZ and lacI each have a promoter -three: lacZ, lacY and lacA each have a promoter
one: one promoter controls expression of lacZ, lacY and lacA
Which of the following terms or descriptions apply to the Lac Repressor? Select all that apply. inducer molecule signaling molecule repressor protein enzyme that metabolizes lactose regulatory sequence activator protein positive regulator negative regulator
repressor protein; negative regulator
During oogenesis (select all that apply) -all methylation patters on chromosomes are erased -some methylation patterns are erased -erased methylation patters are reintroduced according to the gender of the individual making the oocytes, e.g. female for eggs, male for sperm -erased methylation patters are reintroduced according to the gender of the person who passed on the chromosome to the individual making the oocytes, female for the homologous chromosome inherited from mom, male for the homologous chromosome inherited from dad.
all methylation patters on chromosomes are erased erased methylation patters are reintroduced according to the gender of the individual making the oocytes, e.g. female for eggs, male for sperm
Which of the following sequences contains a CpG site? 5'-ATCGTCCGG-3' 5' ATCAGCTACGC-3' all of the above none of the above
all of the above
The lac repressor is inactivated by what molecule? lactose cAMP allolactose tryptophan glucose
allolactose
Tryptophan is an essential amino acid an activator protein a repressor protein a nucleic acid
an essential amino acid
A protein binds to a regulatory sequence and blocks the ability of a transcription factor from binding to a nearby enhancer sequence. This protein would be considered to be: a positive regulator a transcription factor a repressor protein an insulator-binding protein
an insulator-binding protein
The lac repressor -binds to the operator sequence and blocks transcription of the lac operon. -binds to the operator sequence and promotes transcription of the lac operon. -binds to the CAP site and promotes transcription of the lac operon. -binds to the CAP site and blocks transcription of the lac operon.
binds to the operator sequence and blocks transcription of the lac operon.
ZFP57 is a maternally imprinted gene involved in insulin production. A woman with a form of diabetes is homozygous for a mutation in ZFP57. Her partner is homozygous for a wild type allele. They have 4 children.(assume Mendelian ratios and no additional environmental influences) Which of the following is true? Question options: no children will have diabetes only sons will have diabetes 50% of children will have diabetes, irregardless of sex all children will have diabetes only daughters will have diabetes
no children will have diabetes
