Biology Ch. 12 Mastering – Flashcards
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Nucleoli are present during _____.
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interphase -Nucleoli are present during interphase
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Cytokinesis often, but not always, accompanies _____.
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telophase -Cytokinesis often, but not always accompanies telophase.
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Chromosomes become visible during _____.
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Prophase -During prophase, the chromatin fibers become discrete chromosomes.
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Centromeres divide and sister chromatids become full-fledged chromosomes during _____.
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anaphase -During anaphase, sister chromatids separate and daughter chromosomes migrate to opposite poles.
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Spindle fibers attach to kinetochores during _____.
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prometaphase -attachment of spindle fibers to kinetochores is one of the events of prometaphase
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During prophase a homologous pair of chromosomes consists of _____.
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two chromosomes and four chromatids. -at this point each of the chromosomes consists of two chromatids.
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During _____ both the contents of the nucleus and the cytoplasm are divided
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the mitotic phase -the mitotic phase encompasses both mitosis and cytokinesis
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During _____ the cell grows and replicates both its organelles and its chromosomes.
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interphase -these are the events of interphase
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Which event does not take place before the start of mitosis?
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The nuclear envelope disintegrates -this event takes place during mitosis
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True of False? Mitosis takes place during M phase, which is the longest phase of the cell cycle.
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False -Mitosis does indeed take place during M phase, but M phase is the shortest phase of the cell cycle.
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Which term describes two recently replicated DNA strands that are joined together just before cell division?
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Sister chromatids -Sister chromatids are the two strands of a recently replicated chromosome that will be split apart during cell division.
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During which stage of mitosis are chromosomes lined up in the center of the cell?
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Metaphase -Chromosomes held by spindle fibers are lined up in the middle of the cell during metaphase, the third and middle stage of mitosis
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Which stage of mitosis is characterized by the disintegration of mitotic spindles and the formation of two new nuclear membranes?
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Telophase -the mitotic spindles disintegrate and a nuclear envelope begins to form around each set of chromosomes during telophase, the last substage of mitosis
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To which part of the centromere do mitotic spindle fibers attatch during prometaphase?
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Kinetochore -The kinetochore is the region of the centromere on the sister chromatid to which the mitotic spindle attaches.
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During which substage of mitosis do sister chromatids break apart and start moving to opposite poles of the cell?
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Anaphase -Chromatids are pulled to opposite poles of the cell during anaphase, the fourth substage of mitosis
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Which of these is NOT a carcinogen?
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cigarette smoke, fat, UV light, testosterone, all of the above are carcinogens -all of these substances can cause cancer
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___ is a carcinogen that promotes colon cancer
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fat -a diet high in fat increases the risk of both colon and breast cancer
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Which of the following is a function of the S phase in the cell cycle?
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The synthesis of sister chromatids -DNA replication occurs during S phase and results in two sister chromatids for each original chromosome
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The copying of chromosomes occurs during which of the following phrases of the cell cycle?
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S phase -Chromosomes must undergo replication before mitosis can occur; this copying occurs during the S phase
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For the first several divisions of early frog embryos, cells proceed directly from the M phase to the S phase and back to M without gaps. Which of the following is likely to be true about dividing cells in early frog embryos?
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The cells get smaller with each generation. -Without gap phases, the cells have no opportunity to grow
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True of false? The M phase is characterized by the replication and division of a cell's chromosomes
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True -Correct: Cells replicate their chromosomes during the S phase and divide partition their chromosomes during the M phase
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If an organism normally has 34 chromosomes, how many molecules of DNA should there be in the G1 phase of the cell cycle?
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34 -There is one DNA molecule per chromosome
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Which of the following events would cause the cell cycle to arrest?
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Poor nutrient conditions -Poor nutrient conditions would arrest the cell cycle at the G1 checkpoint.
