MITOSIS: REPLICATION OF EUKARYOTIC CELLS
Mitosis and cytokinesis are often referred to collectively as "cellular division." Why are they
more accurately called cellular replication?
The result of mitosis is production of two cells (replicates) identical to the parent cell. The
material is replicated rather than divided.
Does the cell cycle have a beginning and an end?
The organization of our study of cellular events indicates a beginning and end, but the events
continue to repeat.
If a nucleus has eight chromosomes during interphase, how many chromosomes does it
During metaphase there are 8 double-stranded chromosomes.
How many does it have after mitosis is complete?
After mitosis (and separation of chromatids) there are 16 chromosomes distributed between two
Why would we choose an embryonic mass of cells for procedure 13.3 in which to study the
stages of mitosis?
embryonic cells are replicating and growing rapidly
Which stage of mitosis most often is associated with the beginning of cytokinesis?
usually late anaphase
What region of a root has the most mitotic activity?
meristem, just above cap
Why is pinching of the cytoplasm inadequate for cytokinesis in plant cells?
Pinching of cytoplasm is not appropriate for rigid cell walls.
Locate a plant cell in late telophase. What is the volume of the new cells relative to a mature
Each cell is smaller (approximately 1/2) than the parent cell.
Why are the combined data from all the class members more meaningful than your results
Combined results reduce random error.
How accurate were your predictions for length of each stage of mitosis?
probably not close
What sources of error can you list for this technique to determine the time elapsed during
stage of mitosis?
variation in onion roots; student's ability to distinguish stages; microscopic cross sections of
may or may not pass through the nuclear material
MEIOSIS: REDUCTION DIVISION AND GAMETOGENESIS
Why would shuffling genetic material and producing new combinations of characteristics be
advantageous to a species?
New genetic combinations allow adaptation to changing environments.
When would it be deleterious?
New combinations always produce a percentage of disadvantageous characteristics; the risk of
bad gene combinations may be inappropriate in a stable, beneficial environment.
Synapsis occurs after chromosomal DNA has replicated. How many chromatids are
crossing-over of a homologous pair of chromosomes?
Suppose synapsis occurred between two homologous chromosomes, and one had alleles for
blue eyes and brown hair and the other had alleles for green eyes and blonde hair. How many
different combinations of these alleles would be possible?
4 Remember that crossing-over does not necessarily occur between the loci, so the original
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