cell bio final
Indicate whether each of the following is true for meiosis, mitosis, both, or neither.
-formation of a bivalent (meiosis) -genetically identical products (mitosis) -condensation of chromosomes(both) -segregation of all paternal chromosomes to one cell (neither) -involvement of DNA replication (both)
Cells can pause in G1 when DNA is damaged, and can pause in S when there are replication errors. Indicate whether the mechanism below applies to a G1 arrest, an S-phase arrest, both types of arrest, or neither.
-p53 activates the transcription of a Cdk inhibitor.( G1 arrest) -Cyclins are phosphorylated and destroyed. (neither) -Cdk is unable to phosphorylate its substrates.(both) -The Cdc25 phosphatase is inhibited (s-phase)
Name the three key mechanisms important for maintaining the organization of cells into tissues.
1. cell communication 2. selective cell-cell adhesion 3. cell memory
aster mictrotubules
1. interact with the cell cortex 2.depolymerize to promote anaphase B
kinetochore microtubules
1. link chromosomes to a spindle pole depolymerize to promote anaphase A
Meiosis is a highly specialized cell division in which several events occur in a precisely defined order. Please order the meiotic events listed below.
1.chromosome replication 2.chromatid pairing 3.homolog pairing 4.formation of chiasmata (chiasmata = plural of chiasma 5.chromosome condensation 6.alignment of chromosomes at the metaphase plate 7.degradation of cohesins bound to chromosome arms 8.loss of cohesins near centromeres
You examine a worm that has two genders: males that produce sperm and hermaphrodites that produce both sperm and eggs. The diploid adult has four homologous pairs of chromosomes that undergo very little recombination. Given a choice, the hermaphrodites prefer to mate with males, but just to annoy the worm, you pluck a hermaphrodite out of the wild and fertilize its eggs with its own sperm. Assuming that all the resulting offspring are viable, what fraction do you expect to be genetically identical to the parent worm? Assume that each chromosome in the original hermaphrodite is genetically distinct from its homolog.
1/16
A diploid cell containing 32 chromosomes will make a haploid cell containing ___ chromosomes.
16
_________ triggers the separation of sister chromatids by promoting the destruction of cohesins.
Anaphase Promoting Complex
Which of the following statements is true?
Another name for the fertilized egg cell is the zygote
Which of the following statements about apoptosis is true?
Apoptosis is promoted by the release of cytochrome c into the cytosol from mitochondria.
Which of the following statements about integrins is false?
Integrins use adaptor proteins to interact with the microtubule cytoskeleton.
Which of the following statements about the anaphase-promoting complex (APC) is false?
It is continuously active throughout the cell cycle
A double strand DNA breakage will induce PUMA expression, which will in turn promote apoptosis by inhibiting _____.
Bc12
Which of the following statements about gap junctions is false?
Because gap junctions do not allow ions to pass through, they are not used for electrically coupling cells.
You create cells with a version of Cdc6 that cannot be phosphorylated and thus cannot be degraded. Which of the following statements describes the likely consequence of this change in Cdc6?
Cells will be unable to complete DNA synthesis.
Which of the following statements about tumor suppressor genes is false?
Cells with one functional copy of a tumor suppressor gene will usually proliferate faster than normal cells.
Which of the following statements about collagen is false?
Collagen synthase organizes the mature collagen molecules into ordered collagen fibrils.
Which of the following statements about kinetochores is true?
Kinetochores assemble onto chromosomes during late prophase.
Which of the following statements most correctly describes meiosis?
Meiosis involves a single round of DNA replication followed by two successive cell divisions
MPF activity was discovered when cytoplasm from a Xenopus M-phase cell was injected into Xenopus oocytes, inducing the oocytes to form a mitotic spindle. In a control experiment, Xenopus interphase cytoplasm was injected into oocytes and shown not to induce the formation of a mitotic spindle. Which of the following statements is not a legitimate conclusion from the control experiment?
Components of an interphase nucleus are insufficient to cause mitotic spindle formation
Irradiated mammalian cells usually stop dividing and arrest at a G1 checkpoint. Place the following events in the order in which they occur
DNA damage accumulation of cyclic- cdi complexes production of p21 inhibition of cyclin -cdk complexes
Which of the following statements about meiosis is true?
During meiosis, the paternal chromosomes pair with the maternal chromosomes before lining up at the metaphase plate.
Which of the following protein associates with the tumor suppressor Rb?
E2F
. _____ belongs to a group of molecules called mitogen, stimulates cell division by releasing the molecular brakes that keep cells in the G0 or G1 phase of the cell cycle.
EGF
How do reproductive cloning and therapeutic cloning differ?
Embryos are placed into foster mothers during reproductive cloning but not during therapeutic cloning.
the four phases of cell cycle
G1 S G2 and M
You engineer yeast cells that express the M cyclin during S phase by replacing the promoter sequence of the M cyclin gene with that of S cyclin. Keeping in mind that yeast cells have one common Cdk that binds to all cyclins, which of the following outcomes is least likely during this experiment?
G1 cyclins will be expressed during S phase.
Which organelle fragments during mitosis?
Golgi apparatus
Which of the following statements about the experiment diagrammed in Figure Q19-38 is true?
If you crossed all the round-seeded pea plants from the F2 generation with true-breeding wrinkle-seeded pea plants, you would get more round-seeded pea plants in the next generation than if you crossed all the round-seeded pea plants from the F1 generation with true-breeding wrinkle-seeded pea plants.
Which of the following statements is true?
In anaphase B, microtubules associated with the cell cortex shorten.
APC is a tumor suppressor and acts in the Wnt signaling pathway to prevent the TCF complex from turning on Wnt-responsive genes. Mice that lack the gene encoding TCF4 do not have the ability to maintain the pool of proliferating gut stem cells needed to renew the gut lining. What do you predict will happen in mice that lack the APC gene?
Mice lacking the APC gene will have inappropriate proliferation of gut stem cells.
Which of the following statements about cellulose is false?
Microtubules are directly attached to the outside surface of the plasma membrane to form tracks that help orient the cellulose polymers.
which of the following statements is false?
Motor proteins walking along the cytoskeleton are important for the contractile ring that guides formation of the new cell wall.
Which of the following statements is false?
Mutations in somatic cells are passed on to individuals of the next generation.
_______ is called survival factor because it inhibits apoptosis by regulating members of the Bcl-2 family of proteins.
NGF
Which of the following statements about the cell cycle is false?
Once a cell decides to enter the cell cycle, the time from start to finish is the same in all eukaryotic cells.
The formation of a bivalent during meiosis ensures that
all four sister chromatids remain together until the cell is ready to divide
Which of the following could be considered a true-breeding strain for the seed-shape phenotype? (See Figure Q19-38.)
all of the wrinkle-seeded plants produced in the F2 generation
Proteoglycans in the extracellular matrix of animal tissues
allow cartilage to resist compression.
When introduced into mitotic cells, which of the following is expected to impair anaphase B but not anaphase A?
an antibody against the motor proteins that move from the minus end of microtubules toward the plus end
Tissues are organized mixtures of many cell types with certain basic requirements. Which of the following is not one of them?
apoptotic machinery
Induced pluripotent stem (iPS) cells
are created by the expression of a set of key genes in cells derived from adult tissues so that these cells can differentiate into a variety of cell types.
Tight junctions
are formed from claudins and occludins.
Loss-of-function mutations
are usually recessive.
Condensins
assemble into complexes on the DNA when phosphorylated by M-Cdk.
Which of the following precede the re-formation of the nuclear envelope during M phase in animal cells?
assembly of the contractile ring
In which phase of the cell cycle do cells check to determine whether the DNA is fully and correctly replicated?
at the end of G2
Hemidesmosomes are important for
attaching epithelial cells to the extracellular matrix.
Programmed cell death occurs
by means of an intracellular suicide program.
Many features of _____ cells make them suitable for biochemical studies of the cell-cycle control system. For example, the cells are unusually large and are arrested in a G2-like phase.
egg
The extrinsic apoptotic pathway will be initiated by the binding of the Fas ligand presented on the cytotoxic T lymphocyte. Upon the death ligand binding to death receptor, initiator caspases will be activated that will in turn activate _____.
excusioner caspase
Mitogens are
extracellular signals that stimulate cell division.
Adenoma is less dangerous than Adenocarcinoma because ________________.
its cells don't migrate and colonize
A malignant tumor is more dangerous than a benign tumor because
its cells invade other tissues.
Plasmodesmata
permit small molecules to pass from one cell to another
what would be the most obvious outcome to repeated cell cycle consisting of S phase and M phase only
the cell produced will get smaller and smaller
At the start of mitosis (exploring mode), M-cdks phosphorylate Microtubule binding proteins and thus increases ________ of MT. Then, MTs from each pole interact and become stabilized: forming interpolar microtubule.
the dynamic instability
A friend declares that chromosomes are held at the metaphase plate by microtubules that push on each chromosome from opposite sides. Which of the following observations does not support your belief that the microtubules are pulling on the chromosomes?
the jiggling movement of chromosomes at the metaphase plate
Which of the following is not an example of a connective tissue?
the layer of photoreceptors in the eye
Which type of junction contributes the most to the polarization of epithelial cells?
tight junctions
Both multicellular plants and animals have
tissues composed of multiple different cell types.
The artificial introduction of three key ______________ into an adult cell can convert the adult cell into a cell with the properties of ES cells.
transcription factors
. A mutation that introduces a stop codon immediately after the start codon of Adenomatous Polyposis Coli (APC) gene will promote certain cancers.
true
A chromosomal translocation that will swap the inhibitory domain of c-Abl with an unrelated protein and thus constitutively activates Abl tyrosine kinase activity will promote tumorigenesis.
true
A mutation in EGFR that constitutively increases its tyrosine kinase activity will promote tumorigenesis.
true
A mutation in the promoter of Wnt gene, causing the Wnt protein to be transcribed and translated at an abnormally high level will promote certain cancers.
true
A mutation on the small GTPase Ras that hampers GTP hydrolysis makes it oncogenic.
true
Microtubule-dependent motor proteins and microtubule polymerization and depolymerization are mainly responsible for the organized movements of chromosomes during mitosis.
true
_______ is called a member of growth factors because it stimulates cell growth and an increase in cell mass.
PDGF
The survival, proliferation, and size of each cell in an animal are controlled by extracellular signal molecules secreted by neighboring and distant cells. One of these signal molecules bind to ____, a cell-surface receptor and trigger various intracellular signaling pathways.
PDGFER
Which of the following statements is false?
Proteoglycans are a major component of compact connective tissues but are relatively unimportant in watery tissues such as the jellylike substance in the interior of the eye.
Which of the following statements about animal connective tissues is true?
Proteoglycans can resist compression in the extracellular matrix.
Which of the following statements about the benefits of sexual reproduction is false?
Sexual reproduction permits enhanced survival because the gametes that carry alleles enhancing survival in harsh environments are used preferentially during fertilization
Which of the following statements about genome-wide association studies (GWAS) is false?
Studies using GWAS only examine SNPs that occur very rarely (<0.001%) in the population, as those SNPs are most likely to cause disease.
Which of the following statements is false?
The activating phosphatase (Cdc25) removes all phosphates from mitotic Cdk so that M-Cdk will be active.
Which of the following descriptions is consistent with the behavior of a cell that lacks a protein required for a checkpoint mechanism that operates in G2?
The cell would enter M phase under conditions when normal cells would not.
Which of the following statements is false?
The cleavage furrow always forms in the middle of the cell.
Imagine meiosis in a diploid organism that only has a single chromosome. Like most diploid organisms, it received one copy of this chromosome from each of its parents and the two homologs are genetically distinct. If only a single homologous recombination event occurs during meiosis, which of the following choices below correctly describes the four gametes formed.
Two of the gametes will have chromosomes identical to the chromosomes found in the original diploid cell, while two of the gametes will have chromosomes that are different.
Both budding yeast and the bacteria E. coli are unicellular life. Which of the following statements explains why budding yeast can undergo sexual reproduction while E. coli cannot.
Unlike E. coli, budding yeast can alternate between a diploid state and a haploid state.
Which of the following does not describe a situation of asexual reproduction?
Using in vitro fertilization to combine a sperm and an egg to create an embryo.
Which of the following statements about the round-seeded pea plants obtained in the F2 generation is false?
We expect 25% of these plants to be homozygous for the seed-shape allele.
Which of the following is not good direct evidence that the cell-cycle control system is conserved through billions of years of divergent evolution?
Yeast cells have only one Cdk, whereas humans have many Cdks.
Finding co-inheritance of a SNP variant and a disease tells scientists that
a gene important for causing the disease is linked to the SNP.
Ras is a GTP-binding protein that is often defective in cancer cells. A common mutation found in cancer cells causes Ras to behave as though it were bound to GTP all the time, which will cause cells to divide inappropriately. From this description, the normal Ras gene is
a proto-oncogene
Which of the following would not lead to aneuploidy during meiosis?
a reciprocal rearrangement of parts between nonhomologous chromosomes (for example, the left arm of Chromosome 2 exchanging places with the right arm of Chromosome 3)
A metastasis is
a secondary tumor in a different part of the body that arises from a cell from the primary tumor.
During fertilization in humans,
a wave of Ca2+ ions is released in the fertilized egg's cytoplasm.
Which type of junction involves a connection to the actin cytoskeleton?
adherens junctions
After the first meiotic cell division
cells are produced that contain the same number of chromosomes as somatic cells.
The principal microtubule-organizing center in animal cells is the
centrosome.
During recombination
chiasmata hold chromosomes together.
At the end of DNA replication, the sister chromatids are held together by the
cohesins.
Which of the following molecules is not found in plants?
collagen
Mouse embryonic stem (ES) cells
come from the inner cell mass of early embryos.
Ehlers-Danlos syndrome, a genetic disorder lacking collagenase which converts procollagen to collagen, will affect ____.
connective tissue
CDK stands for
cyclin dependent kinase
Levels of Cdk activity change during the cell cycle, in part because
cyclin levels change during the cycle.
During sexual reproduction, novel mixtures of alleles are generated. This is because
during meiosis, the segregation of homologs is random such that different gametes end up with different alleles of each gene.
Do you agree or disagree with the following statement? Explain your answer. A trait that is found at a low frequency in the population has to be a recessive trait.
disagree
A cell with nuclear lamins that cannot be phosphorylated in M phase will be unable to
disassemble its nuclear lamina at prometaphase.
Cells in the G0 state
do not divide.
Progression through the cell cycle requires a cyclin to bind to a Cdk because
the binding of a cyclin to Cdk is required for Cdk enzymatic activity
In the absence of recombination, how many genetically different types of gamete can an organism with five homologous chromosome pairs produce?
32
If you crossed the round-seeded plants obtained in the F1 generation with a true-breeding strain of wrinkle-seeded plants, how many round-seeded plants would you expect to obtain in the next generation? (See Figure Q19-38.)
50%
Which of the following statements about cancer is false?
A mutation in even a single cancer-critical gene is sufficient to convert a normal cell into a cancer cell.
Which of the following genetic changes cannot convert a proto-oncogene into an oncogene?
A mutation that introduces a stop codon immediately after the codon for the initiator methionine.
What are the main structures providing tensile strength in the following?
A. animal connective tissue (collagen fibers) B. animal epidermis (intermediate filaments) C. plant cell walls (cellulose fibers)
Indicate whether the following molecules are found in plants, animals, or both.
A. intermediate filaments (animals) B. cell walls (plants) C. microtubules (both) D. cellulose (plants) E. collagen (animals)
Consider an animal cell that has eight chromosomes (four pairs of homologous chromosomes) in G1 phase. How many of each of the following structures will the cell have at mitotic prophase?
A. sister chromatids (16) B. centromeres (16) C. kinetochores (16) D. centrosomes (2) E. centrioles (4)
The regulatory component of MPF, called Cyclin, will be Ubiquitylated by _______ .
APC
Which of the following reasons was essential for Mendel's law of independent assortment?
All the traits that Mendel examined involved genes that did not display linkage.
Which of the following statements about Mendel's experiments is false?
All traits that Mendel studied were recessive.
Which of the following statements is false?
The loading of the origin recognition complexes (ORCs) is triggered by S-Cdk.
Which of the following statements about plant cell walls is true?
The microtubule cytoskeleton directs the orientation in which cellulose is deposited in the cell wall.
Which of the following statements is true?
The mitotic spindle helps segregate the chromosomes to the two daughter cells.
Which of the following events does not usually occur during interphase?
The nuclear envelope breaks down.
Which of the following reasons was essential for Mendel to disprove the theory of blended inheritance?
The traits that Mendel examined involved an allele that was dominant and an allele that was recessive.
Is the following statement true or false? Explain. Somatic cells leave no progeny and thus, in an evolutionary sense, exist only to help create, sustain, and propagate the germ cells
True
There are organisms that go through meiosis but do not undergo recombination when forming haploid gametes. Which of the following statements correctly describes the gametes produced by such an organism. (Assume that these organisms are diploid, that each of the two homologous chromosomes are genetically distinct as typically found in the wild, and that these organisms have more than one chromosome.)
This organism could potentially produce 2n genetically distinct gametes, where n is its haploid number of chromosomes
The single-nucleotide polymorphisms found in the human population
can be linked into haplotype blocks.
Adherens junctions
can be used to bend epithelial sheets into tubes.
A pluripotent cell
can give rise to all the tissues and cell types in the body.
Cells that are terminally differentiated
can no longer undergo cell division.
An adult hemopoietic stem cell found in the bone marrow
can undergo self-renewing divisions for the lifetime of a healthy animal.
Apoptosis differs from necrosis in that necrosis
causes cells to swell and burst, whereas apoptotic cells shrink and condense.
MPF activity was found to be oscillate during the cell cycle, although the amount of its kinase component, called _______, remained constant.
cdk
CAK stands for __________.
cdk activating kinase
The concentration of mitotic cyclin (M cyclin)
falls toward the end of M phase as a result of ubiquitylation and degradation.
Gene amplification of a tumor suppressor gene PTEN is more dangerous than gene amplification of a proto- oncogene.
false
Is the following statement true or false? The phenotype of an organism reflects all of the alleles carried by that individual.
false
The centromere nucleates a radial array of microtubules called an aster
false
______ produce the extracellular matrix of connective tissue.
fibrosis
The plasmodesmata in plants are functionally most similar to which animal cell junction?
gap junction
Which of the following does not occur during M phase in animal cells?
growth of the cell
Which of the following would not explain the results with the mutant?
inability to begin M phase
You have isolated a strain of mutant yeast cells that divides normally at 30°C but cannot enter M phase at 37°C. You have isolated its mitotic cyclin and mitotic Cdk and find that both proteins are produced and can form a normal M-Cdk complex at both temperatures. Which of the following temperature-sensitive mutations could not be responsible for the behavior of this strain of yeast?
inactivation of an enzyme that ubiquitylates M cyclin
The Retinoblastoma (Rb) protein blocks cells from entering the cell cycle by
inhibiting cyclin transcription
A cell can crawl through a tissue because of the transmembrane
integrin
. ______ couple the extracellular matrix to the cytoskeleton inside the animal cell.
integrins
At desmosomes, cadherin molecules are connected to
intermediate filaments.
The G1 DNA damage checkpoint
involves the inhibition of cyclin-Cdk complexes by p21.
a basal lamina
is a thin layer of extracellular matrix underlying an epithelium
Somatic cells
leave no progeny.
Studies with Xenopus eggs identified a partly purified activity called MPF that drives a resting Xenopus oocyte into M phase. MPF stands for _____.
maturation promoting factor
Cadherins
mediate cell-cell attachments through homophilic interactions.
Which word or phrase below best describes the phase in mitosis depicted in Figure Q18-41?
metaphase
Haplotype blocks can be seen in humans because
modern humans descended from a relatively small population of about 10,000 individuals that existed about two thousand generations ago.
Disassembly of the nuclear envelope
must occur for kinetochore microtubules to form in animal cells
Disassembly of the nuclear envelope
must occur for kinetochore microtubules to form in animal cells.
In addition to stimulatory factors, some signal proteins such as ________ act negatively on other cells, inhibiting their survival, growth, or proliferation.
myostatin
If you crossed the round-seeded plants obtained in the F1 generation with a true-breeding strain of round-seeded plants, how many wrinkle-seeded plants would you expect to obtain in the next generation? (See Figure Q19-38.)
none
nduced pluripotent stem (iPS) cells ______________________.
none of the above
A preparative period of the cell cycle called _________ consists of three subphases
nterphase
Which of the following statements about cancer is false?
oncogene cooperation
Which of the following protein will be expressed by tumor suppressor p53?
p21
The activity of a Cdk can be blocked by the binding of____, a Cdk inhibitor.
p27
DNA damage can arrest the cell cycle in G1 by stabilizing _____.
p53
The epidermis (skin) is renewed from ________.
pluripotent stem cells in its basal layer
When a terminally differentiated cell in an adult body dies, it can typically be replaced in the body by a stock of
proliferating precursor cells.
Fibroblasts organize the collagen of the extracellular matrix by
pulling the collagen into sheets or cables after it has been secreted.
One way in which mitogens stimulate cell proliferation is activating G1-Cdk which in turn inhibits ______.
rb
A stem cell divides into two daughter cells. One of the daughter cells goes on to become a terminally differentiated cell. What is the typical fate of the other daughter cell?
remains a stem cell
Cytokinesis in animal cells
requires ATP.
interpolare microtubules
stabalized by interactions with each other via motor proteins
An individual that arises by reproductive cloning has a nuclear genome that is identical to
the adult who donated the cell for nuclear transplantation.
A major distinction between the connective tissues in an animal and other main tissue types such as epithelium, nervous tissue, or muscle is _______________.
the amount of extracellular matrix in connective tissues.
Organisms that reproduce sexually
undergo a sexual reproductive cycle that involves an alternation of haploid cells with the generation of diploid cells
________ is a kinase that inhibit M-Cdk.
weel
A single nondisjunction event during meiosis
will involve the production of two normal gametes if it occurs during meiosis II