BI 203 tophat questions
On a typical prokaryotic chromosome, one would find how many telomeres?
0, prokaryotes don't have telomeres
Considering complementary base pairing, how many hydrogen bonds do guanine and cytosine make?
3
What's the correct sequence for PCR? 1. Annealing — Cool to allow primers to form hydrogen bonds with ends of target sequence 2. Extension — DNA polymerase adds nucleotides to the 3' end of each primer 3. Denaturation — Heat briefly to separate DNA strands
3-1-2
The human genome is distributed across ______ chromosomes
46
If n represents one copy of single-stranded genomic DNA, then which of the following represents the amount of DNA in a typical cell at G2 of the cell cycle?
4n
A molecule that is not membrane permeable binds to a membrane protein on the outside of a cell. This changes the conformation of the protein, causing the binding site to face the inside of the cell. The molecule is then released into the cell and the conformation of the binding site changes again so that it is outside the cell. This is a description of what type of transport(er)?
A membrane carrier
Voltage-sensitive K+ channels are 1000 times more permeable to K+ than to Na+ because...
A selectivity filter removes the water molecules from K+ ions but not from Na+ ions.
Why is telomerase important in cancer cells?
Abnormal increases in telomerase activity can allow tumor cells to replicate telomeres and keep proliferating indefinitely
Mutations in the internalization signal of endocytic receptors prevent their interaction with...
Adaptor proteins
A feature common to most transmembrane proteins is...
An alpha helical region composed of 20-25 hydrophobic amino acids
What is the simplest cell model to study DNA replication?
Bacteria
What is involved in assembling actin filaments?
Begins with formation of an aggregate of three actin monomers, polymerization occurs from both the plus and minus ends. It does NOT require ATP
If a human gene is found to have 5 introns, then the mature mRNA encoded by that gene would have how many exons?
Between 1 and 6
What is false about tRNAs? a. tRNAs are ~70-80 bps long and form a cloverleaf structure b. all tRNAs have a CCA sequence at their 3' terminus c. tRNAs differ in sequence only at the anticodon d. there are several modified bases present in mature tRNAs
C.
The characterization of restriction endonucleases was a key step in the development of recombinant DNA technology. What is the function of these enzymes?
Cleavage of double stranded DNA at specific sequences
Antibiotics are powerful medications that inhibit the growth of bacteria. They work at a variety of levels, but many target the process of protein synthesis in the bacterial cell. In the developing of an antibiotic, which of the following would be an effective strategy or target for the drug? a. Inhibition of translational initiation b. Induction of premature polypeptide chain termination c. Inhibition of aminoacyl tRNA binding d. All of the above
D
What's an example of symport?
Epithelial cells in the intestine are able to take up glucose by coupling this reaction with the uptake of two molecules of sodium.
All molecules that are in the nucleus are transported by a process that requires GTP. T/F?
False
Sigma subunits of bacterial RNA polymerase initiate binding to the DNA and are released from the polymerase at the end of transcription. T/F?
False
The generation of ATP by the mitochondrial ATP synthase is an active transport process. T/F?
False
In polysacharides, sugars are linked together by means of what kind of bonds?
Glycosidic
What is phosphorylated by the Cdk1/cyclin B complex during mitosis?
Golgi matrix proteins, nuclear lamins, and codensins
What technique is used to inactivate a gene by altering the DNA that encodes it?
Homologous recombination
Where do transgenic mice carry foreign genes?
In all of their cells
What's an example of endocrine signaling?
Insulin release by beta cells in pancreas, mediating an effect of glucose uptake by muscle cells
Which of the following is not one of the four major classes of organic molecules in the cell?
Ions
What is true of cyclin B?
It is a component of MPF, it accumulates throughout S and G2, and it activates the Cdk1 protein kinase
What is true of cylcin D?
It is required of cell cycle progression, its expression is induced by growth factors, and it is rapidly degraded following the removal of appropriate growth factors
In the "pulse-chase" experiment, Palade and colleagues studied the pathway taken by newly secreted proteins in pancreatic acinar cells by labeling them with radioactive amino acids and then determining their progressive location within the cells. What is the correct order in which proteins were identified?
RER -> Golgi -> secretory vesicles
It is generally believed that Earth's original cell enclosed a self-replicating ___ molecule.
RNA
What's not involved in the tissue-specific expression of the immunoglobulin heavy-chain gene?
RNA pol II
What are the two families of small GTP-binding proteins that are involved in the formation of coated vesicles?
Rab and ARF
You perform an experiment by incubating a radiolabeled nucleotide into the medium of a culture of cells. The cells that take up the radiolabel would be expected to be in what phase of the cell cycle?
S phase
What's true of introns?
They are a part of a gene but they are absent from the corresponding mRNA
What is true about cis-acting elements is true?
They are specific DNA sequences that control the transcription of adjacent genes, various proteins specifically recognize and bind to them.
What is true about ion channels?
They open either by the binding of ligands or by changes in electrical potential
What is the function of karyopherins?
They transport macromolecules into or out of the nucleus.
Partial digestion of chromatin with micrococcal nuclease was found to yield DNA fragments approximately 200 base pairs long. What accounts for this phenomenon?
This result suggests that the binding of proteins to DNA in chromatin protects regions of DNA from nuclease digestion
What is the normal function of dystrophin in muscle cells?
To attach actin filaments to the plasma membrane
What are some functions of the cytoskeleton?
To provide a structural framework for the cell, cell locomotion, and intracellular movements of organelles and other structures
The process by which proteins are made from RNA templates is called...
Translation
Many cancers arise as a result of a breakdown in signaling pathways that control cell proliferation T/F?
Tru
The citric acid cycle consists of the oxidation of ______ to produce ________.
acetyl CoA; NADH and FADH2
cAMP is synthesized from ATP by the action of...
adenylyl cyclase
Estimates of mutation rates for a variety of genes indicate that the frequency of errors during replication is much lower than would be predicted on the basis of complementary base pairing. Which of the following mechanisms accounts for the higher degree of fidelity? a. conformational changes in DNA pol b. 3'-5' exonuclease activity of DNA pol c. requirement of a primer for DNA synthesis by DNA pol
all of the above
The directionality of nuclear protein import is determined by...
an unequal distribution of Ran/GTP
What is the complementary sequence to the following bases? 5'-ACGAGG-3' a. 5'-ACGAGG-3' b. 5'-CCTCGT-3' c. 5'-GGAGCA-3' d. 5'-TGCTCC-3'
b.
What is the complementary sequence to the following? 3'-ACCTGATG-5' a. 5'-CATCAGGT-3' b. 5'-GTAGAGGT-3' c. 5'-TGGACTAC-3' d. 5'-GTAGTCCA-3'
c.
Which of the following correctly describes a cDNA molecule? a. a DNA copy of genomic DNA sequence synthesized by the enzyme reverse transcriptase b. the nucleic acid portion of a ribosome c. a DNA copy of an RNA sequence synthesized by the enzyme reverse transcriptase
c. a DNA copy of an RNA sequence synthesized by the enzyme reverse transcriptase
Glucose repression (or catabolite repression) is mediated by several positive transcriptional control mechanisms. What is not one of those mechanisms?
cAMP-activated CAP transcribes genes that metabolize lactose
The major cation responsible for regulating actin-myosin contraction is...
calcium
The major site at which membrane lipids are synthesized is the...
cytosolic side of the ER membrane
Which of the following statements about transmembrane proteins is true? a. The signal sequences are always cleaved off. b. They are always inserted with the amino terminus on the lumenal side and the carboxyl terminus in the cytosol. c. They cross the membrane only once. d. They usually have one or more alpha-helices spanning the membrane bilayer.
d. they usually have one or more alpha-helices spanning the membrane bilayer
The response initiated by protein kinase A is terminated by...
dephosphorylation of phosphotproteins by protein phsophatase 1
Cholesterol, a membrane lipid in animals, has a chemical structure similar to...
estrogen and testosterone
A pseudogene is a...
gene that arose through duplication but become nonfunctional by acquiring mutations
A reporter gene is used to...
identify regulatory sequences from the upstream regions of other genes.
Most cells in an adult animal are...
in the G0 phase
The lac operon in E. coli is regulated by lactose, which...
inactivates a repressor of transcription and prevents it form binding to the lac operon and inhibiting transcription
Point mutations in DNA result from....
incorporation of incorrect bases during replication and changes as a result in chemical exposure and radiation exposure
What is not a commonly observed consequence of the binding of a signaling molecule to its cell surface receptor?
increased synthesis of the receptor
In cell fractionation experiments in which subcellular organelles are separated on the basis of their density, the smooth endoplasmic reticulum is ___ the rough endoplasmic reticulum.
lighter than
LINEs
long interspersed elements,
What best describes the ability of an enhancer to mediate transcription from very distant sites?
looping of the DNA can occur, allowing the transcription factor to get into the proximity of the RNA pol
What is not a destination for vesicles leaving the Golgi apparatus?
mitochondria
What distinguishes the mitochondrial and nuclear human genomes?
most mitochondrial DNA nucleotides encode for protein
What is the difference between neurotransmitters and neuropeptides?
neurotransmitters are small hydrophilic molecules and neuropeptides are small proteins
Which of the following classes of amino acids is buried within the folded structure of the protein?
nonpolar
What transport mechanism can bring whole cells into a cell?
phagocytosis
SH2 domains are...
protein domains that bind phosphotyrosine-containing peptides
The initiator codon in prokaryotes is...
recognized via the Shine-Dalgarno sequence.
homologous recombination
recombination between segments of DNA with homologous nucleotide sequences
the nucleolus is the site where....
ribosomal RNA is transcribed and ribosomes are partially assembled
A protein's alpha helices and beta sheets fold together to create an overall shape at the ___ level of protein structure.
tertiary
The trans-Golgi network is...
the exit part of the Golgi where sorting of proteins to the lysosomes, plasma membrane, and cell exterior occurs
A centrosome is....
the major microtubule organizing center in animal cells
About 50% of the mass of most biological membranes consists of lipids and about 50% consists of proteins. Therefore,
the membranes contain more molecules of lipid than proteins because lipids are lower in molecular weight
Whether a microtubule shrinks or grows is determined by...
the rate of GTP-bound tubulin addition relative to the rate of tubulin GTP hydrolysis
G protein-coupled receptors are important molecules involved in signal transduction. What's true about them?
they generally contain seven membrane-spanning alpha helices
The primary function of rRNAs in the ribosome is...
to catalyze peptide bond formation
The function of telomeres is...
to ensure chromosome replication and maintainence
Passive transport across a membrane refers to...
transfer in the energetically favorable direction
The progression from metaphase to anaphase is triggered by....
ubiquitin mediated proteolysis of key proteins
The G2 cell cycle checkpoint detects...
unreplicated or damaged DNA
What is not involved in protein transport into the mitochondria?
vesicular transport
What is the simplest cell model to study nuclear targeting of proteins?
yeast
