Download MCDB 1041 Class 3 Mitosis

MCDB 1041 Class 3 Mitosis
The pictures below show a cell going through the different phases of mitosis. Describe in the space under each
cell what is happening (generally) to the chromosomes during this phase of mitosis. Also note when
chromosomes are replicated, and when not.
Stage? Interphase Prophase Metaphase Anaphase Telophase Chromosomes replicated? Yes (replicate in S phase) and remain replicated until anaphase: at anaphase, the chromosomes are N O LONGER replicated. They have separated. Anything else happening? Chromosomes condense align pulled apart Centrioles migrate centrioles set up the spindle fibers that will pull apart the chromosomes You have a plastic container representing the nucleus of a cell. Rearrange the contents of the cell so that you
have a total of 4 chromosomes, 2 chromosomes of each size. Leave the extra chromosomes that may have been
in your cell on the desktop to use later. The different colors indicate that the two copies of each chromosome are
non-identical; they also represent the fact that you inherit one set of chromosomes from each of your parents (a
“green parent” or a “pink parent”, for example). The different kinds of chromosomes (1,2,3 or 4) are indicated
by different lengths of paper.
1.
Your plate of papers is meant to be a model of a human nucleus, with just a few chromosomes to keep it
simpler. In the nucleus of a real somatic human cell, how many chromosomes are there?
46
2.
What is the goal of mitosis?
To make an exact replica of the original cell
All cells undergo mitosis as an embryo is forming. Some cells continue to undergo mitosis even in an adult.
Only the cells that will make sperm and egg undergo meiosis (we’ll learn about that next week).
Replicate each chromosome by selecting matching color and size paper pieces from the extra chromosomes.
3. a) Look at one replicated chromosome. It is comprised of two sister chromosomes (also referred to as
sister chromatids).
Are the sister chromosomes different from each other? NO-identical
Do they have the same genes? yes
Do they have the same alleles? yes
b) What term describes the pink and green #1 chromosomes? homologous
Are the pink and green #1 chromosomes different from each other? Yes, in that they don’t
necessarily have the same alleles
Do they have the same genes? yes
Do they have the same alleles? Not necessarily
4. Align all the replicated chromosomes of this cell as if they were in metaphase of mitosis. Draw the
replicated chromosomes below in the larger circle, showing how they will align in the middle of the cell
in preparation for mitsois. Then, in the two cells shown below the larger cell, draw the chromosomes in
the two daughter cells.
See the powerpoint slides (or your book)!
5. After separation of the chromosomes into two new cells, are the two cells identical with respect to their
genetic content?
YES
6. How was the alignment of the chromosomes important for whether or not the two daughter cells were
identical? What kinds of problems might occur in the daughter cells if the alignment were imperfect?
If they didn’t align centered over the metaphase plate, so that one chromatid can be pulled to each new cell, you
might end up with different # and kinds of chromosomes in the two cells—so the process of aligning and
separating is important for the two cells to end up identical.