2). Most eukaryotic organisms have ______________ chromosomes in their cells.
d). over 1,000 Answer:b
3). Replicate copies of each chromosome are called _____________ and are joined at the _________________.
b). sister chromatids/kinetochore
c). sister chromatids/centromere
d). homologues/kinetochore Answer:c
4). During which phase of the cell cycle is DNA synthesized?
d). M Answer:c
5). Chromosomes are visible under a light microscope
a). during mitosis.
b). during interphase.
c). when they are attached to their sister chromatids.
d). All of these are correct. Answer:a
6). During mitosis, the sister chromatids are separated and pulled to opposite poles during which stage of mitosis?
d). telophase Answer:c
7). Cytokinesis is
a). the same process in plant and animal cells.
b). the separation of cytoplasm and the formation of two cells.
c). the final stage of mitosis.
d). the movement of kinetochores. Answer:b
8). The eukaryotic cell cycle is controlled at several points; which of these statements is not true?
a). Cell growth is assessed at the G1/S checkpoint.
b). DNA replication is assessed at the G2/M checkpoint.
c). Environmental conditions are assessed at the Go checkpoint.
d). The chromosomes are assessed at the spindle checkpoint Answer:c
9). What proteins are used to control cell growth specifically in multicellular eukaryotic organisms?
d). growth factors Answer:d
10). What causes cancer in cells?
a). damage to genes
b). chemical damage to cell membranes
c). UV damage to transport proteins
d). All of these cause cancer in cells. Answer:a
Test Your Visual Understanding
1). Match the mitotic and cell cycle phases with the appropriate figure.
1). An ancient plant called horsetail contains 216 chromosomes. How many homologous pairs of chromosomes does it contain? How many chromosomes are present in its cells during metaphase? Answer: 108 homologous pairs; 432 sister chromatids
2). Colchicine is a poison that binds to tubulin and prevents its assembly into microtubules; cytochalasins are compounds that bind to the ends of actin filaments and prevent their elongation.
What effects do you think that these two substances would have on cell division in animal cells? Answer: Because cell division in animal cells relies on microtubules to pull sister chromatids apart to opposite poles of the cell, colchicine would disrupt the lining up and separating of sister chromatids. Cell division of animal cells also relies on actin filaments to cinch the cell in two during cytokinesis, cytochalasins would disrupt cytokinesis in animal cells.
3). If you could construct an artificial chromosome, what elements would you introduce into it, at a minimum, so that it could function normally in mitosis? Answer: An artificial chromosome would need to have DNA with an area characteristic of the centromere region, histones and related proteins necessary for condensation, and kinetochores (proteins that associate with centromeres and microtubules). With these structures, the chromosomes would be able to respond to cellular structures in mitosis.