Bio 172 Exam 3 quizzes

how is DNA organized in eukaryotes?

DNA is wound around histone spools to form nucleosomes

what mechanism brings the chromosomes to the metaphase plate?

chromosomes are captured by microtubules from both centrosomes and are pulled in both directions simultaneously

what happens in prophase

chromosomes condense and become visible

DNA methylation leads to ___ chromatin and gene ___

closed; inactivation

Using current DNA sequencing technology, it is possible to sequence an entire chromosome (250 million nucleotides) as one long molecule

false

methylation is a way to temporarily silence genes

false

what is responsible for pulling apart the double stranded DNA when running a PCR reaction?

heat

ato separate the template strands in PCR, you need ___. To separate the template strands in cellular DNA replication you need ___.

heat; helicase

proteasomes

help to regulate protein levels

what is true?

histone acetylation correlates with active transcription

pairs of chromosomes in the human genome that match in size and appearance are called

homologous

how is signal transduction in a phosphorylation cascade terminated?

phosphatases remove phosphate groups from proteins

which of the following steps in a signal transduction pathway involves signal amplification?

phosphorylation cascade

epigenetic mechanisms of gene regulation include

chemical modifications to DNA

signaling pathways must be terminated. Termination of signaling can include which of the following?

-secondary messengers are degraded -detachment of signaling molecule from the receptor -phosphatases -GTP hydrolysis by G proteins not: ATP hydrolysis by receptor tyrosine kinases

which of the following statements is true regarding epimutations in the SUPERMAN gene in the plant Arabidopsis thaliana?

-DNA methylation keeps the gene silent -the silent state of the gene is heritable from one plant generation to the next -the DNA sequence of the gene is not changed false: the silent state of the gene is heritable from one plant generation to the next

Which of the following about DNA methylation is true?

-DNA methylation patterns can be copied following DNA replication -DNA methylation is associated with condensed chromatin -most DNA methylations are reset during gametogenesis false: DNA methyltransferases add methyl groups to histones

which of the following is true of G protein coupled receptor signaling?

-G protein hydrolyzes GTP to GDP to become inactive -G protein is inactive when bound to GDP -non hydrolyzable analog of GTP would cause the G protein to be permanently activated false: the signal indirectly responsible for g protein activation is hydrophobic

In a mutant mouse cell line, normal amounts of HOX-3 mRNA are produced, but the mRNA is shorter than normal. In addition, no functional HOX-3 protein is produced. Which of the following is consistent with these observations?

-a change in splicing -a mutation in a gene (other than HOX-3) that produces a protein that binds to the HOX-3 3'UTR -a mutation in a miRNA which binds to the HOX-3 mRNA

which of the following components of gene regulatory mechanisms is used in eukaryotes?

-alternative splicing -regulatory proteins binding to DNA sequences -histone methylation -DNA methylation not used: operons

which of the following descriptions of a cell cycle phase is correct?

-anaphase: chromosomes move to opposite ends of the cell -prometaphase: nuclear envelope breaks down -interphase: centrosomes replicate -telophase: chromosomes decondense incorrect: metaphase: centromeres divide

second messengers

-are degraded in order to terminate a cellular signaling response -plays a role in activation of intracellular signal transduction -amplify the effects of the signal -are small intracellular molecules that participate in signal transduction -include cAMP and Ca++

which of the following is considered a secondary messenger?

-cAMP -IP3 -DAG not: phospholipase c-beta

which of the following is a common feature of binary fission and mitotic cell division?

-cellular growth -pinching of the parent cell into two daughter cells by the cytoskeleton or cytoskeleton like proteins -DNA synthesis not: construction of a nuclear envelope

which of the following is a common feature of bacterial cell division cycle and the plant cell division cycle?

-chromosomes are separated -DNA synthesis -tubulin or tubulin like proteins participate in the process -cellular growth not: cytoskeleton or cytoskeleton like proteins form a ring at the constriction

which of the following is considered translational control of protein synthesis?

-controlling when a protein is synthesized -controlling the location of where a protein is synthesized -controlling the rate of protein synthesis not: controlling the primary protein sequence

which of the following occurs during mitosis?

-decline in M cyclin concentration -chromosomes condense -nuclear envelope breakdown not: DNA replication

what is true regarding polycistrony

-expression of polycistronic genes can be controlled by DNA binding proteins -polycistronic mRNA is found only in prokaryotes -more than one protein can be translated from a single mRNA -each of the genes on a polycistronic mRNA contains a start and stop codon - false: polycistronic DNA is controlled by multiple promoters

which of the following is an example of epigenetics?

-genomic imprinting in mammals -methylation of DNA leading to gene silencing -DNMTs recognize and methylate hemimethylated DNA false: mutation

Which is an example of a post translational event?

-insertion of an integral membrane protein into the plasma membrane -protein folding -addition of copper cofactor to an enzyme not: removal of introns

which is true about a hydrophilic signaling molecule

-its effect is transduced across the cell but the signal never enters the cell itself -they may bind G protein coupled receptors

the M cyclin CDK complex

-phosphorylates proteins that promote formation of the mitotic spindle -initiates many events of mitosis -triggers phosphorylation of certain nuclear proteins, resulting in breakdown of the nuclear envelope during prophase -controls the cell cycle during M phase

which of the following is an example of posttranslational modification of a protein?

-phosphorylating proteins -adding a covalent functional groups such as a carbohydrate -marking proteins for degradation not: changing the mRNA codon sequence

which one of the following is an activity attributed to the checkpoint regulated by the G1/S cyclin-CDK complex in mammals?

-radiation damage to DNA activates phosphorylation of a p53 protein, preventing its export from the nucleus -protein complexes involved in DNA replication are activated -radiation damage to DNA results in the inhibition of the G1/S cyclin-CDK complex and blocks progression of the cell cycle to S phase -excess p53 in the nucleus increases expression of an inhibitor of CDK activity not: histone expression is inhibited, allowing replication to proceed

which type of receptor undergoes a conformational change upon ligand binding?

-receptor kinase -G protein coupled receptor -intracellular receptor -ligand gated ion channel

Which type of receptor is membrane associated?

-receptor kinase -ligand gated ion channel -G protein coupled receptor

which site is disqualified from consideration in a cloning strategy?

-restriction site in the selective marker -restriction site in the middle of the gene -restriction site that occurs more than once in the vector not disqualified: restriction site in the multiple cloning site (MCS)

what is a requirement for successful cell division?

-the parent cell must have enough cytoplasmic components to contribute to the daughter cells -each daughter cell must receive all equal genetic material -the parent cell must be large enough to divide into two not: the parent cells must be in quiescent state

translation can be controlled by which mechanisms?

-the ribosome is phosphorylated in response to viral invasion -a miRNA binds to the mRNA to inhibit translation -a protein binds to the 3' UTR of an mRNA to control the efficiency of translation

what is true about sister chromatids?

-they are identical or nearly identical DNA sequences -they are attached to each other at the centromere -they are formed in the S phase of the cell cycle when the chromosome undergoes replication false: they are formed when the prokaryotic circular chromosome attaches at the plasma membrane

You discover a new bacterium and you wish to sequence its genome using shotgun sequencing. Among the many DNA sequences, you obtain the four fragments shown below. 1. TAGCTTACGGT 2. ATACGTCCGAT 3. ATGCATTAG 4. CGGTACGTATA The order the fragments would have been found in the original bacterial genome is

3-1-4-2

You run a PCR reaction for 5 cycles starting with a single DNA duplex. How many copies of your sequence will you synthesize?

32

You are cloning a gene in the lab, and you wish to use restriction enzymes that recognize palindromic DNA sequences. Single strands of DNA representing restriction site sequences are shown below. Which of the below restriction sites is not a palindrome?

5' ACGGCA 3' is: 5' AATATT 3'

what would be a compatible end for joining to the one shown below? 5' CTTAA 3' G

5' CTTAA 3'G

Consider the signaling pathway below: A --> B --> C --> D --> target gene activation Now add an inhibitor that acts to prevent signal A from producing B. Which compound(s) could be added to activate target gene expression? Answer all that apply.

B, C, D

In Discussion example 2, imagine that you are given a different drug to test. Data below show its ability to increase PKC activity. Which component of the pathway is the drug mimicking?

DAG

Cells of the accessory gland in the fruit fly Drosophila melanogaster are binucleate, meaning they have two nuclei in one cytoplasm. Each nucleus has the normal amount of DNA expected in a fruit fly cell. What could have resulted in the production of these binucleate cells?

DNA replication and mitosis took place, but cytokinesis was skipped

what is a nucleosome?

DNA wrapped around a group of histone proteins

What is the correct order of steps in a PCR reaction?

Denature the DNA, anneal DNA primers, extend the chain with DNA polymerase

non dividing cells are arrested in which phase of the cell cycle?

G0

the correct sequence of steps in the eukaryotic cell cycle is:

G1, S phase, G2, mitosis, cytokinesis

one difference between eukaryotic and prokaryotic cell division is

In eukaryotes chromosome replication must be complete before chromosome separation begins, while in prokaryotes chromosomes separate as they are being replicated

One difference between PCR and DNA sequencing is

PCR needs two different primers, which DNA sequencing only needs one primer

microRNA (miRNA) and small interfering RNA (siRNA) are incorporated into a protein complex called

RISC (RNA induced silencing complex)

When comparing the expression of the LIN-28 gene in two different cell types, you notice that both cell types make the same amount of mRNA. They also produce the same amount of protein, but the protein is much shorter in one cell type than in the other. Which of the following regulatory mechanisms is consistent with these observations?

RNA editing

___ results in chemical modifications to RNA bases, which can lead to changes in the amino acid sequence of the protein

RNA editing

In an E coli mutant beta-galactosidase is expressed at high levels whether or not lactose levels are high. which of the following can explain this phenotype?

a mutation in the operator which prevents Lacl binding to it

in terms of gene expression, what is a repressor molecule?

a molecule that does not allow transcription to occur

Assume you have a mutation that affects gene expression in the Lac operon. This mutation leads to no/low gene expression when glucose levels are low and lactose levels are high. Which of the following mutations could explain this expression pattern?

a mutation in the Lacl gene, such that the repressor protein is made but it is unable to bind lactose

what is an inducer molecule?

a molecule that can prevent a repressor protein from inhibiting transcription

what is a inducer molecule?

a molecule that can prevent a repressor protein from inhibition transcription

what is meant by the term homologous chromosomes?

a pair of chromosomes, each carrying the same set of genes

In Discussion example 1, which of the answer choices would prevent transcription of the target gene in the presence of a valid signal?

a protein that degrades cAMP in the cytoplasm

what is meant by a checkpoint in biology?

a regulatory mechanism that pauses the cell cycle until preparations are complete and necessary repairs are made

in negative regulation

a regulatory molecule (protein) binds to the DNA near the gene in order to prevent transcription

an operator is

a regulatory region in DNA; the binding site for the repressor

which of the following is true of binary fission

a ring of tubulin like proteins leads to cytokinesis

what is a miRNA

a small regulatory RNA that forms a hairpin structure

which of the following can lead to changes in chromatin structure and is often associated with activation of transcription?

addition of acetyl groups to lysines located in the histone tail

posttranslational modifications include

addition of phosphate groups to amino acid side chains in the protein

what do kinases do?

add phosphate groups to other molecules

a steroid hormone uses a receptor protein that has two binding sites, one is a ligand binding site and the other is a DNA binding site. what type of receptor is this?

an intracellular receptor

a long string of codons for amino acids, uninterrupted by a stop codon is called

an open reading frame

what is true?

as chromosomes become more condense, the diameter of sister chromatids increases

the signaling cell and the responding cell are one in the same in

autocrine signaling

which of the following correctly lists the types of cellular communication from shortest to longest distance travelled by the signaling molecule to reach its responding cell?

autocrine, paracrine, endocrine

replica plating was used to find mutant E coli that cannot utilize lactose as a food source because

bacteria with the desired mutation will not grow on lactose only plates

during cytokinesis in an organism, tubulin like proteins form a ring and constrict the cell. This organism is likely to be a

bacterium

why cannot chromosomes line up in the middle of the cell before prometaphase

because the nuclear envelope prevents the microtubules from being able to bind to chromosomes

one key regulator of the cell cyle is CDK. CDK is a protein that

binds to cyclin to become activated

A G-protein coupled receptor activates adenylyl cyclase, which produces cAMP. Therefore, cAMP levels are low in the absence of a signal and high in the presence of a signal. What would happen to cAMP levels if you added a nonhydrolyzable form of GTP?

cAMP levels will be high both in the presence and in the absence of a signal

alternative splicing is very common in eukaryotes. Which of the following, when sequences, would provide evidence of alternative splicing?

cDNA

transgenerational epigenetic inheritance

can happen in both plants and animals; genomic imprinting

which of the following does not occur during interphase?

cell division

What is a key difference between cell signaling by cell surface receptor and cell signaling by an intracellular receptor?

cell surface receptors bind polar signaling molecules; intracellular receptors bind nonpolar signaling molecules

if the p53 gene in cells is mutated, which of the following situations may occur

cells with DNA damage may proliferate in an uncontrolled manner

the technique of Sanger sequencing takes advantage of the fact that dideoxynucleotides (nucleotides in which the 3' hydroxyl group is absent) act as

chain terminators

what is the correct order of steps when performing molecular cloning?

cut DNA with restriction enzyme, ligation, transformation, antibiotic selection

restriction enzymes

cut stretches of DNA at specific sites known as recognition sequences

in DNA methylation in mammals, which nitrogenous base is most frequently methylated?

cytosin

in what state are the chromosomes at the end of telophase

decondense and unattached to the centrosome

a constitutively active gene is

expressed continuously

the E coli Trp operon is regulated by the Trp repressor. When Trp levels are high in the cell, Trp binds to the repressor and this allows the repressor to bind to the operator. What would be the result if the repressor was mutated in such a way that it could no longer bind Trp?

expression of the structural genes in the operon would be high regardless of Trp levels in the cell

___ rely on ___ such as cAMP or DAG to activate a variety of pathways within the cell

g protein coupled receptors; second messengers

What about gene regulation in correct?

genes can be regulated at transcription, post translational, translational, and chromatin structure level false: genes are regulated only in prokaryotes

The CRP-cAMP complex binds the lactose operon when

glucose levels are low and cAMP levels are high

positive and negative transcriptional regulation differ in that

in positive regulation, the binding of a regulatory protein to the DNA is necessary for transcription to occur; in negative regulation, such binding prevents transcription

miRNAs function ___, siRNAs function ___

in the cytoplasm; either in the nucleus or in the cytoplasm

a type of RISC complex can be found in the nucleus. the function of this complex is likely to be

inhibition of transcription

GLD-1 is an RNA binding protein which binds to the 3' UTR of the MES-3 mRNA. If GLD-1 is not functional, MES-3 mRNA levels do not change, but MES-3 protein levels increase. The size of the MES-3 protein does not change, only its quantity. What is the function of GLD-1?

inhibits translation

what is the major function of the mRNA 5' cap?

initiation of translation

cells spend most of their time in what phase?

interphase

How does addition of nonhydrolyzable form of GTP affect G protein coupled receptor signaling?

it activates the pathway

A chaperone responsible for proper folding of an enzyme is missing from a cell. What might happen to that enzyme?

it could be tagged with ubiquitin

A G protein is active when

it is bound to GTP

if a cell is exposed to high temperatures and a large amount of protein misfolding will kill the cell, why is modifying ribosomal activity a good strategy for cell preservation?

it would prevent a large number of misfolded proteins from accumulating within the cell

which of the following types of signaling depends on direct cell-cell contact?

juxtacrine

You are studying a signaling pathway that involves a receptor, a G-protein, and a kinase in the lab. What would you expect if you replace all available ATP with non-hydrolyzable ATP?

kinase target proteins would not get phosphorylated

which gene encodes the protein beta-galactosidase?

lacZ

what modification takes place when lactose is present in a bacterial cell?

lactose induces a conformational change in the repressor protein

the lacZ and lacY genes are transcribed when

lactose is present and glucose levels are low

what is one common feature between G protein coupled receptor signaling and steroid hormone receptor signaling?

ligand binding leads to conformational change in both types of receptors

which of the following has a an inhibitory effect on transcription?

methylation of cytosines in DNA

the gene E01G4.3 is regulated by a short RNA. You notice that when the short RNA is not present, mRNA levels do not change, but protein levels of E01G4.3 increase. This short RNA is likely to be a

miRNA

A photobleaching experiment was presented in class showing that the distance between the bleached area and the chromatids shortened. What explanation could be given if the distance between the bleached area and the centrosome shortened?

microtubules shorten at the centrosome

in animal cells, ___ plays an important role during anaphase, and ___ is important during cytokinesis

microtubules; actin

what happens in telophase?

nuclear envelopes reform around newly segregated chromosomes

acetylation happens

on histone proteins

a cell in the G1 phase of the cell cycle has __ centrosomes, and a cell in the G2 phase of the cell cycle has ___ centrosomes

one, two

if you performed a PCR reaction but accidentally only added one of the two primers, what would the product be?

only one DNA strand will be synthesized

what would be the effect of mutation in p53 that prevents its phosphorylation?

p53 would be unable to halt the cell cycle in response to DNA damage

cAMP binds to the CRP protein and activates the protein. In other words, cAMP regulates CRP

posttranslationally

during which stage of mitosis does the nuclear envelope break down

prometaphase

the nuclear envelope breaks down in ___, and it reforms in ___

prometaphase, telophase

restriction enzymes are made of ___; restriction sites are found in ___

protein; DNA

an operon is a

region of DNA consisting of the promoter, operator, and coding sequences for structural proteins

which mechanism of gene regulation is used only in eukaryotes and not in prokaryotes

regulation of chromatin structure by modifying histones

siRNA is a type of ___ RNA

regulatory

in prokaryotes, regulatory proteins called __ bind to DNA sequences called ___ to regulate expression of genes

repressors; operators

which of the following immediately follows receptor activation in a signaling pathway?

signal transduction

In communication between cells, the ___ produces the signaling molecule, also know as the ___; the ___ produces the ___, to which the signaling molecule binds

signaling cell; ligand; responding cell; receptor

when a ___ reaches its ___, there is a specific means of receiving it and acting on the message. this task is the responsibility of specialized proteins called ___.

signaling molecule; target cell; receptors

electrophoresis separates DNA fragments on a gel according to

size

what is siRNA?

small interfering RNA, an example of a short regulatory RNA

what is true about receptors in signaling pathways

some receptors are transmembrane proteins, some others are intracellular proteins

in paracrine signaling, the signal affects only

target cells close to the cell from which it was secreted

the DPY-27 protein in nematode larvae is 340 amino acids long, but in adults it is 270 amino acids long. What could cause this difference?

the DPY-27 mRNA is edited in adults, but not in larvae

Praeder-Willi syndrome is a genetic disease, caused by a mutation in a gene subject to genomic imprinting. Disease only develops if the mutation is inherited from the father. What can you conclude from these observations?

the allele inherited from the mother is not expressed

You are observing levels of beta galactosidase production in bacteria under different environmental conditions. You record the following results: High glucose, high lactose High High glucose, low lactose Low Low glucose, high lactose High What could account for the result observed above?

the bacteria have a mutation in the gene that codes for CRP, such that CRP does not need to bind to cAMP to be actiated

the C-value paradox explains

the disconnect between genome size and organismal complexity

cytokinesis is

the division of the parent cell into two daughter cells

which of the following genes might not be constitutively expressed?

the gene encoding stress hormone

where does the signal bind to the receptor?

the ligand binding site

the centrosome is

the microtubule organizing center for the mitotic spindle

an added complication to bacterial cell division that is not present in animal cells is

the need to create a new cell wall

You look at a cell under the microscope and see nicely condense chromosomes in the nucleus. What would you expect to happen next?

the nuclear envelope would break down

what is interphase?

the period of time between two successive M phases

what is the kinetochore

the site where the chromosomes attach to the microtubules

negative transcriptional regulation means that

there is a regulatory factor that turns off transcription

positive transcriptional regulation means that

there is a regulatory factor that turns on transcription

what is a major role for the 3' UTR in mRNA

translational regulation

Which of the following protein domains is present in G protein coupled receptor but not in a steroid hormone receptor?

transmembrane domain

DNA sequences that can replicate and inset themselves randomly into new places in the genome are called

transposable elements

a skin cell in G2 of interphase has __ as much DNA as it had in G1

twice

directional cloning is dependent on

using different restriction enzymes to cut on either side of a gene

how is a new cell wall formed in dividing plant cells?

vesicles originating from the Golgi apparatus are used to form a cell plate