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Mastering Biology Chapter 12 The Cell Cycle

Dr. Wiens Assigments from www.masteringbiology.com
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Which of the following is a function of the S phase in the cell cycle?
The synthesis of sister chromatids,
DNA replication occurs during S phase and results in two sister chromatids for each original chromosome.
The copying of chromosomes occurs during which of the following phases of the cell cycle?
S phase
Chromosomes must undergo replication before mitosis can occur; this copying occurs during the S phase.
True or false? The M phase is characterized by the replication and division of a cell's chromosomes.
False
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?
The cells get smaller with each generation.
Without gap phases, the cells have no opportunity to grow.
If an organism normally has 34 chromosomes, how many molecules of DNA should there be in the G1 phase of the cell cycle?
34
There is one DNA molecule per chromosome.
Which of the following events would cause the cell cycle to arrest?

Poor nutrient conditions

Chromosomes lined up along the metaphase plate

Synthesis of cyclins by growth factors and activation of a cyclin-Cdk complex

Complete chromosome replication
Poor nutrient conditions would arrest the cell cycle at the G1 checkpoint.
During _____ both the contents of the nucleus and the cytoplasm are divided.
the mitotic phase
During _____ the cell grows and replicates both its organelles and its chromosomes.
interphase
DNA Replication produces 2 identical DNA molecules called_____, which separate during mitosis.
sister chromatid(s)
After chromosomes condence, the _____ is the region where the identical DNA molecules are most tightly attracted to each other.
centromere(s)
During mitosis, microtubules attach to chromosomes at the _____.
kinetochore(s)
In dividing cells, most of the cell's growth occurs during _____.
interphase
The _____ is a cell structure consisting of microtubules, which forms during early mitosis and plays a role in cell division
mitotic spindle(s)
During interphase, most of the nucleus is filled with a complex of DNA & protein in a disperced form called _____.
chromatin
In most eukaryotes, division of the nucleus is followed by _____, when the rest of the cell divides.
cytokinesis
The_____ are the organizing centers for microtubules involved in separating chromosomes during mitosis.
centronome(s)
•In prophase
the microtubules of the spindle apparatus begin to assemble from individual tubulin subunits. As the identical chromatids of each pair of sister chromatids condense during this stage, they are held together by cohesin proteins.
•Prometaphase is marked by
fragmentation of the nuclear envelope, expansion of the spindle into the nuclear region, and attachment of some spindle fibers to the chromosomes via the kinetochores.
•Metaphase, marked by
the alignment of chromsomes along the metaphase plate, is brought about by kinetochores aligning and then remaining motionless relative to the poles of the cell.
•In anaphase
the cohesin proteins are cleaved, and the kinetochores move toward the poles of the cell, separating the sister chromatids.
•As telophase proceeds
, the kinetochore microtubules of the spindle disassemble. As the chromosomes reach the poles of the cell, the nuclear envelopes of the two new daughter nuclei form.
During prophase, the microtubules of the mitotic spindle : Lengthen, Shorten, or Disassemble?
Lengthen
Nucleoli are present during _____.
Nucleoli are present during interphase.
Cytokinesis often, but not always, accompanies _____.
Cytokinesis often, but not always, accompanies telophase.
Chromosomes become visible during _____.
During prophase, the chromatin fibers become discrete chromosomes.
Centromeres divide and sister chromatids become full-fledged chromosomes during _____.
During anaphase, sister chromatids separate and daughter chromosomes migrate to opposite poles.
Spindle fibers attach to kinetochores during _____.
Attachment of spindle fibers to kinetochores is one of the events of prometaphase
During prophase a homologous pair of chromosomes consists of _____.
two chromosomes and four chromatids