Biol CH 9-12 LC Questions
To study the cell cycle, you use different chemicals to arrest your cells in the different stages and then observe them under the microscope. Match each chemical with the stage that it acts on.
-Chemical 1 interferes with the initial formation of the mitotic spindle. - Prophase -Chemical 2 interferes with the formation of the cleavage furrow. - Cytokinesis -Chemical 3 inhibits the enzymes that cleave cohesins (protein complexes that regulate separation of sister chromatids). - Anaphase -Chemical 4 blocks the binding of microtubules to the kinetochores of the sister chromatids. - Metaphase -Chemical 5 interferes with DNA synthesis. - Interphase- S phase Chemical 1 interferes with the formation of the mitotic spindle. This would interfere with prophase since the mitotic spindle begins to form during this stage of mitosis. Chemical 2 interferes with the formation of the cleavage furrow. Since the cleavage furrow in animal cells is responsible for cytokinesis, this would be the stage that chemical 2 affects. Chemical 3 inhibits the enzymes that cleave cohesins. Cohesins must be cleaved for the sister chromatids to separate in anaphase, so chemical 3 would interfere with anaphase. Chemical 4 blocks the binding of microtubules to the kinetochores. Microtubules grow and begin binding chromosomes during prometaphase/ metaphase, so this phase would be affected by chemical 4. Chemical 5 interferes with DNA synthesis which takes place during S phase of interphase and must be complete before the cell can proceed to G2/ divide.
How many chromosomes are present in this cell? How many chromatids? Assuming the cell is diploid, how many homologous pairs? (three blue X and three grey X) A. 12,6,6 B. 6,12,3 C. 4,4,2 D. 6,12, 6
B
Which of the following are true of interphase? A. Nuclear envelope fragments B. Nuclear envelope encloses the nucleus C. DNA is replicated D. Division of genetic material E. Division of the cytoplasm F. Sister chromatids separate and each chromatid becomes a full-fledged chromosome G. Two centrosomes form to organize the microtubles of the spindle H. Chromosomes condense into discrete chromosomes
B, C, and G The nuclear envelope encloses the nucleus in interphase and breaks down during late prophase (or prometaphase). Two centrosomes are formed during G2 of interphase. DNA is replicated during interphase, but division of genetic material and the cytoplasm occur during M phase (telophase/ cytokinesis). Chromosomes begin to condense and appear as sister chromatids during prophase and separate during anaphase.
Which of the following is TRUE of an organism that has a chromosome number 2n=16? A. The species is diploid with 32 chromosomes per cell B. The species has 16 sets of chromosomes per sell C. Each somatic cell in this organism has 8 pairs of homologous chromosomes D. During the S phase of the cell cycle there will be 32 separate chromosomes E. gamete from this species has 4 chromosomes
C.
This SEM of a highly condensed, duplicated human chromosome might have been taken during which of the following stages of the cell cycle? A. G1 B. S C. G2 D. prophase E. metaphase F. anaphase G. telophase H. cytokinesis
D and E Chromosomes should be duplicated from end of S/ beginning of G2 through metaphase. However, duplicated chromosomes are only condensed like this at end of prophase and metaphase.
Scientists can determine the stage of the cell cycle by labeling a cell's DNA with a fluorescent dye and then measuring DNA content. Suppose a non-dividing cell has 80 pg of DNA. Sketch a graph showing how that cell would progress through one round of the cell cycle.
a horseshoe shape (longer on the left side)
