exam 3
All of these events happen during M phase except: a. formation of the spindle. b. condensation of the chromosomes. c. synthesis of DNA. d. separation of sister chromatids.
c
During meiosis crossing over takes place between: a. non-sister chromatids. b. any two chromatids. c. sister chromatids. d. nonhomologous chromosomes. e. nonhomologous chromatids.
a
Approximately what percentage of the human genome consists of repetitive DNA or transposable elements? a. 50 percent b. 25 percent c. 5 percent d. 1 percent e. 10 percent
a
In normal meiosis, when do homologous chromosomes separate from each other? a. in the first meiotic division b. They may separate in either the first or second meiotic divisions. c. in the second meiotic division
a
On which strand are new nucleotides being added in the same direction as the replication fork is opening? a. the leading strand b. the lagging strand c. On both strands, DNA synthesis is proceeding in the same direction as the replication fork.
a
On which strand is DNA synthesis discontinuous, occurring in fragments that are later connected? a. the lagging strand b. Both strands synthesize DNA in fragments. c. the leading strand
a
The genetic information of daughter cells is the same as the genetic information of the parent in binary fission. a. true b. false
a
There is no correlation between genome size and complexity of an organism. a. true b. false
a
What effect does each successive mutation have on the colon cells in the example? a. It causes them to divide more rapidly than normal cells. b. In causes them to become larger and expand in the colon. c. It causes them to become non-colon cells. d. It causes them to leave the colon and spread to other tissues.
a
What happens if the conversion of GTP into GDP by the G protein is inhibited? a. The amplification reaction continues until ATP levels are too low. b. Phosphatases dephosphorylate the target proteins of protein kinase A. c. cAMP molecules are degraded into AMP. d. Polar ligands stop binding G protein-coupled receptors.
a
What is the function of AP endonuclease? a. It cleaves the DNA backbone in two places. b. It prevents the single strands from forming double-stranded DNA. c. It cleaves the incorrect base from the deoxyribose sugar. d. It incorporates cytosine into the single-strand gap.
a
Which enzyme relieves the tension on the double helix during DNA replication? a. topoisomerase b. a single-stranded binding protein c. DNA polymerase d. an RNA primer e. helicase
a
Which is true? a. Errors in chromosome segregation can occur in either the first or second meiotic division. b. Nondisjunction can only produce gametes with extra chromosomes, not missing chromosomes. c. Down syndrome is caused by errors in fertilization. d. Down syndrome is the one inherited disorder that results from an extra copy of an entire chromosome.
a
Which of the choices is not needed for DNA replication? a. ribosomes b. nucleotides c. DNA d. enzymes e. None of the answer options is correct.
a
Which type of reaction is carried out by adenylyl cyclase? a. cyclization of ATP into cAMP b. phosphorylation of a protein target c. hydrolysis of ATP into ADP d. phosphorylation of GDP into GTP
a
Why are the ends of microfilaments and microtubules called "plus ends" and minus ends"? a. Because monomers are added more quickly to one end (the "plus end") than they are to the other end (the "minus end"). b. Because polymerization occurs at one end (the "plus end") and depolymerization occurs at the other end (the "minus end"). c. Because monomers can be added to one end only (the "plus end"), and can only be removed from the other end (the "minus end"). d. Because the actin and tubulin monomers that make up microfilaments and microtubules have evolved more rapidly than most other proteins.
a
Why does a heterozygous loss-of-function mutation in the BRCA1 gene increase an individual's risk for breast and ovarian cancer? a. It results in unrepaired DNA damage and an increase in accumulated mutations. b. It results in the activation of an oncogene (a gene that causes cancer). c. It causes cells to replicate and divide without stopping. d. It causes cells to become malignant.
a
Beneficial mutations can: a. protect from disease. b. never be reversed. c. permit an organism to become adapted to its environment. d. None of the other answer options is correct.
a and b
Which answer choices could account for the increased cell division and cancer in the patient? a. The concentration of a signaling molecule in the patient is higher than in non-cancer cells. b. The cells taken from the patient have a reduced level of signal amplification. c. The cells taken from the patient have more growth factor receptors than normal. d. None of the other answer options is correct.
a and c
A virus is surrounded by a protein coat known as a(n): a. surface protein. b. capsid. c. protease. d. reverse transcriptase. e. integrase.
b
Actin microfilaments and tubulin-based microtubules are important components of the cytoskeleton that function during mitosis. Which process of cell division would be most affected in animal cells if actin function was blocked? a. The mitotic spindle would not form. b. Cytokinesis would not occur to divide the cytoplasm. c. The sister chromatids would not separate. d. The chromosomes would not replicate
b
Cells differentiate into multiple tissue types because each tissue type has its own unique DNA (cells in that tissue have unique DNA). a. true b. false
b
During DNA replication, the leading strand contains Okazaki fragments. a. true b. false
b
Homologous pairs of chromosomes separate during: a. meiosis I and mitosis. b. meiosis I only c. meiosis II and mitosis. d. mitosis only. e. meiosis II only
b
How would signaling be affected if a mutation caused a G protein to be unable to replace GDP with GTP following the binding of a ligand to the G protein-coupled receptor? a. The signal would not be affected and signaling would occur. b. The signaling would be blocked because replacement of GDP with GTP is required to activate the G protein.check c. The signaling would be blocked because G protein would be active but unable to signal due to the lack of a bound ligand. d. The signaling pathway would be activated even when no ligand was present
b
Many agricultural crops, like wheat, have more than two copies of the genome and are called: a. diploid. b. polyploid. c. prokaryotic. d. haploid. e. unicellular.
b
Predict what happens if each adenylyl cyclase enzyme is able to convert only one molecule of ATP into cAMP, reducing the amount of cAMP produced. a. Not enough cAMP is generated and the cell undergoes signal termination. b. Not enough molecules of protein kinase A are activated and the cellular response is dampened. c. Additional G protein-coupled ligands are expressed to compensate for the reduction in cAMP production. d. Phosphatases are activated to reduce the competition for the target protein of protein kinase A.
b
RNA primase lays down an RNA primer to start DNA replication. If a mutation occurs that blocks the function of RNA primase, which synthesis of which strand is affected, and why? a. The leading strand is affected because it leads DNA synthesis. b. Both strands are affected because all DNA polymerase can only add new nucleotides to a 3′-OH present at the end of the RNA primer. c. The lagging strand is affected because it requires an RNA primer for each Okazaki fragment produced.
b
Ras is most similar to: a. the γ (gamma) subunit of three-subunit G proteins. b. the α (alpha) subunit of three-subunit G proteins. c. the β (beta) subunit of three-subunit G proteins. d. ion channels. e. receptor kinases.
b
These enzymes play important roles in DNA replication: DNA polymerase, primase, ligase, helicase. In what order do they work during replication? a. ligase, helicase, DNA polymerase, primase b. helicase, primase, DNA polymerase, ligase c. DNA polymerase, primase, ligase, helicase d. DNA polymerase, helicase, primase, ligase e. primase, helicase, ligase, DNA polymerase
b
What feature of double-stranded DNA makes it necessary to have a leading strand and a lagging strand during replication? a. the negative charge on the sugar-phosphate backbone b. the antiparallel orientation of the strands c. the hydrogen bonding between bases d. the base stacking of the bases
b
What is the end result of base excision repair? a. The DNA double helix is unwound to allow replication. b. The nucleotide bearing the incorrect base is excised and replaced with a nucleotide bearing the correct base. c. The blunt ends present in double-strand DNA breaks are rejoined. d. Specific bases are removed from the DNA when they are no longer needed.
b
What is the end-result of activating the MAP kinase pathway? a. phosphorylation of multiple cytosolic proteins b. a change in gene expression c. ion flow d. synthesis of second messenger molecules
b
What is the function of uracil glycosylase? a. It binds to the site of a missing base. b. It cleaves uracil from the deoxyribose sugar. c. It cleaves the DNA backbone in two places. d. It replaces the missing nucleotide with one that properly pairs with the base on the opposite strand.
b
Which of the strands use a template for DNA replication? a. the leading strand b. Both strands use a template during DNA replication. c. the lagging strand
b
Which statement about DNA replication is true? a. DNA polymerase performs DNA synthesis on the leading strand, and RNA polymerase performs synthesis on the lagging strand. b. When DNA polymerase reaches a primer from prior DNA synthesis, the primer is removed and replaced with DNA. c. The lagging strand requires an RNA primer to initiate DNA synthesis, whereas the leading strand does not require an RNA primer. d. On the leading strand, new DNA is added to the 3′ end of the growing strand, whereas on the lagging strand, new DNA is added to the 5′ end.
b
The ligand for a G protein-coupled receptor is added to cells, but they exhibit no cellular response. After some tests, you identify ATP levels are lower than normal but GTP levels are not lower than normal. Which process(es) are likely to be affected by this? Select all that apply. a. activation of G protein-coupled receptor b. activation of protein kinase A c. activation of adenylyl cyclase d. activation of G protein
b and c
Becky does not have the mutant BRCA1 allele, but she still develops breast cancer. What might explain this? Select all that apply. a. Becky is really unlucky; the odds of avoiding cancer were not in her favor. b. Becky has another mutation that is also a genetic risk factor for breast cancer. c. Becky contracted breast cancer from her sisters. d. Becky was exposed to certain environmental risk factors for breast cancer.
b and d
A cell in which viral reproduction occurs is called a: a. daughter cell. b. None of the other answer options is correct. c. host cell. d. sex cell. e. somatic cell.
c
A specific ligand is polar in nature. Where is the ligand-binding portion of the receptor most likely to be located? a. cytoplasmic side of the cell membrane b. cytoplasm of the cell c. extracellular side of the cell membrane d. lumen (interior) of the endoplasmic reticulum
c
How do most cancers arise? a. from a single mutation arising simultaneously in a cluster of cells b. from mutations arising in a single cell that are then transmitted to other cells in the body c. from a series of mutations that arise in the descendants of a single somatic cell d. from multiple mutations arising simultaneously in a single cell
c
The point at which DNA synthesis is initiated is called the: a. start codon. b. replication fork. c. origin of replication. d. primer. e. primase.
c
Transposable elements are: a. proteins that can move between cells. b. DNA sequences that can insert themselves into RNA. c. DNA sequences that can insert themselves into new positions within the genome. d. proteins that can move in and out of the nucleus. e. None of the other answer options is correct.
c
What enzyme moves outward from the origin of replication and breaks hydrogen bonds between DNA nucleotides? a. RNA primase b. DNA polymerase c. helicase d. topoisomerase II
c
What is the result of DNA ligase's action? a. DNA is broken up at specific sites. b. DNA is condensed to chromosomes. c. DNA fragments are joined together. d. DNA transcription occurs. e. DNA translation occurs.
c
What is the second role of this enzyme in DNA replication? a. synthesis of RNA primer b. unwinding of the DNA duplex c. proofreading d. stabilizing strands of DNA at a replication fork e. joining Okazaki fragments
c
A diploid plant species has 16 chromosomes. How many chromosomes are in a tetraploid "version" of this plant? In the hexaploid? In the octoploid? a. 16 in the tetraploid, 24 in the hexaploid, and 32 in the octoploid b. 32 in the tetraploid, 48 in the hexaploid, and 56 in the octoploid c. 12 in the tetraploid, 18 in the hexaploid, and 24 in the octoploid d. 32 in the tetraploid, 48 in the hexaploid, and 64 in the octoploid
d
A eukaryotic chromosome has _____ origin(s) of replication, and a bacterial chromosome has ______ origin(s) of replication. a. one; many b. one; one c. many; many d. many; one
d
A lack of telomerase activity limits what? a. the number of Okazaki fragments that can be linked together b. the number of replication bubbles that form during replication c. the rate of DNA replication d. the number of times a cell can divide e. the rate of meiosis
d
A new nucleotide can only be added to the _____ end of a growing DNA strand. DNA therefore always grows in the _____ direction. a. 3'; 3' to 5' b. 5'; 5' to 3' c. 5'; 3' to 5' d. 3'; 5' to 3'
d
Cellular responses that result from receptor kinase activation tend to: a. involve changes in metabolism. b. be short term. c. involve ion channels. d. involve changes in gene expression.
d
Paramecium is a single-cell eukaryotic organism that can reproduce by mitotic cell division. Prior to the M phase of the cell cycle, which of the events must occur? a. Sister chromatids must be separated. b. The cell must first be fertilized. c. The nucleus must divide. d. The cell must replicate its chromosomes. e. The nuclear envelope must disintegrate.
d
Prophase of meiosis I has some important differences from prophase of mitosis. These differences include: ___________ pair, and _________ occurs. a. chromatids; condensation b. chromosomes; separation c. homologous chromatids; separation d. homologous chromosomes; crossing over
d
The concept of reverse transcription was at first very controversial because it: a. suggested that RNA could sometimes function as an enzyme. b. All of these choices are correct. c. showed that viruses could function with an RNA genome. d. contradicted the "central dogma" that the direction of expression of genetic information is always from DNA to RNA to protein. e. implied that DNA could be translated into protein.
d
What is nondisjunction? a. failure of chromosomal pairing b. failure of chromosomal condensation c. failure of chromosomal replication d. failure of chromosomal separation
d
What is the first thing to occur in DNA replication? a. the synthesis of a short RNA primer b. the removal of the RNA primer, which is replaced by DNA c. the extension of DNA from the 3′ end of the RNA primer d. the strands of the DNA double helix are separated
d
Which of the statements about the strands of a newly replicated DNA molecule is correct? a. Both strands are made up of newly assembled nucleotides. b. The sugar-phosphate chains are conserved, and new bases are inserted between them. c. The base pairs are conserved, and new sugar-phosphate backbones are built up on them. d. One strand is new, and the other is from the original molecule. e. Both strands contain some nucleotides from the original molecule.
d
Which property of transposable elements allows them to contribute to the C-value paradox? a. Copies of transposable elements can appear on multiple chromosomes. b. Their replication is controlled by genes found on the transposable elements itself. c. Their copy number can increase from one generation to the next. d. All of these choices are correct.
d
Why are some mutations of Ras associated with cancer? a. Ras is a type of second messenger. b. Ras binds to growth factor receptors. c. Ras alters ion flow across the cell membrane. d. Ras activates the MAP kinase signal transduction pathway that regulates cell division.
d
I. Protein kinase A is activated. II. Ligand binds to G protein-coupled receptor. III. ATP is converted into cAMP. IV. The alpha subunit of the G protein activates adenylyl cyclase. V. GDP is replaced by GTP in the G protein. In what order do the steps for the activation of a cellular response take place? a. I > III > II > IV > V b. III > IV > I > V > II c. V > I > III > II > IV d. IV > II > V > I > III e. II > V > IV > III > I
e
The enzyme responsible for proofreading a growing DNA strand and for replacing mismatched nucleotides is a. topoisomerase II. b. DNA replicase. c. DNA ligase. d. helicase. e. DNA polymerase.
e
Virus genomes can be... a) single-stranded RNA b) single-stranded DNA c) double-stranded DNA d) double-stranded RNA e) All of these choices are correct.
e
What is the function of the enzyme DNA polymerase? a. to synthesize a strand of mRNA using mRNA as a template b. to synthesize a strand of DNA using a polypeptide as a template c. to synthesize a strand of mRNA using DNA as a template d. to synthesize a polypeptide using DNA as a template e. to synthesize a strand of DNA using DNA as a template
e
Why are single-stranded binding proteins necessary for DNA replication? a. None of the answer options is correct. b. They provide the energy necessary to separate the two strands of DNA. c. They direct the primase where to lay down the primer. d. They direct where replication will start. e. They prevent the two parental strands from coming together again.
e