Chapter 18/20 Quiz Questions

final exam

A cell that is terminally differentiated will

dismantle the cell-cycle control system

Which of the following statements is true

mitotic spindle helps segregate the chromosomes to the 2 daughter cells

What would be the most obvious outcome of repeated cell cycles consisting of S phase and M phase only?

the cells produced would be smaller than if G1 was also present

Which word or phrase below best describes the phase in mitosis depicted in Figure 18-2?

metaphase

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

Which of the following components is NOT important for ciliary movement?

sarcoplasmic reticulum

Which of the situations below will enhance microtubule shrinkage?

addition of a drug that inhibits GTP exchange on free tubulin dimers

Which of the following structures shortens during muscle contraction

sarcomeres

Which of the following statements about the function of the centrosome is FALSE?

microtubules emanating from the centrosome have alternating polarity such that some have their plus end attached to the centrosome while others have their minus end attached to the centrosome

You are studying nuclear lamins and use recombinant DNA technology to alter the coding sequence of a nuclear lamin gene. The altered gene codes for a nuclear lamin protein that can no longer be phosphorylated during prophase of mitosis. What do you predict would happen if the cell only had the altered nuclear lamin gene (and not the unaltered version)?

nuclear lamins will no longer disassemble properly during mitosis

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

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

 Which of the following statements about tumor suppressor genes is FALSE?

cells with 1 functional copy of a tumor suppressor gene will usually proliferate faster than normal cells

Which of the following statements about organoids is FALSE?

organoids can only be made for organs that are made up of a single type of differentiated cell

A basal lamina?

is a thin layer of extracellular matrix underlying an epithelium

Which of the following does NOT occur during M phase in animal cells?

growth of the cell

The concentration of mitotic cyclin (M cyclin)

falls toward the end of M phase because of ubiquitylation and degradation

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

The G1 DNA damage checkpoint

involves the inhibition of cyclin-Cdk complexes by p21

Which of the following statements about organellar movement in the cell is FALSE?

only the microtubule cytoskeleton is involved in organellar movement

Figure 17-4A shows how the movement of dynein causes a sperm cell’s flagellum to bend. If the polarity of the adjacent doublets of microtubules is reversed (see Figure 17-4B), what do you predict would happen?

bending would occur, except that the right microtubule doublet would move down relative to the left one

kinesins and dyneins

often move in opposite directions

Which of the following statements about microtubules is true?

motor proteins move in a directional fashion along microtubules by using the inherent structural polarity of a protofilament

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(n)

proto-oncogene

A malignant tumor is more dangerous than a benign tumor because

its cells invade other tissues

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

Cells that are terminally differentiated

can no longer undergo cell division

Part of an epithelial tissue needs to be degraded to allow tumor cells to spread to the rest of the body?

basal lamina

A mutant yeast strain stops proliferating when shifted from 25°C to 37°C. When these cells are analyzed at the two different temperatures, using a machine that sorts cells according to the amount of DNA they contain, the graphs in Figure 18-1 are obtained. Which of the following would NOT explain the results with the mutant?

inability to begin M phase

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

Microtubules are important for transporting cargo in nerve cell axons, as diagrammed in Figure 17-3. Notice that the two types of cargo are traveling in opposite directions. Which of the following statements is likely to be FALSE?

the black cargo and the gray cargo are moving along microtubules of oppsite polarity

Actin-mediated movement involves the coordination of many events in the cell. Which of the following is NOT required for cell crawling?

release of Ca2+ from the sarcoplasmic reticulum

Which of the following conditions would decrease the likelihood of skeletal muscle contraction?

addition of a drug that blocks Ca2+ binding to troponin

Mouse embryonic stem (ES) cells 

come from the inner cell mass of early embryos

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

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

Levels of Cdk activity change during the cell cycle, in part because

cyclin activity changes during the cycle

The retinoblastoma (Rb) protein blocks cells from entering the cell cycle by

inhibiting cyclin transcription

 Which of the following statements about the cytoskeleton is FALSE?

covalent bonds between protein monomers hold together cytoskeletal filaments

Figure 17-7 shows an electron micrograph of a myofibril within a skeletal muscle fiber; various regions and points along the fibril have been labeled. Which of the following statements is true about this myofibril’s contraction?

point B will move closer to point C ?

An adult hemopoietic stem cell found in the bone marrow

can undergo self-renewing divisions for the lifetime of a healthy animal

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