mitosis and meiosis

css 2/10/11

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Key Concepts * Ques * Vocabulary

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Mitosis + cell division

Onion Root tip Activity -


Extra: Cell division -

Wayne's World -




1. Mitosis is the division of the nucleus after the replication of DNA, enough to produce 2 identical daughter cells, each with the exact same
# of chromosomes. eg: Original cell has 46 chromosomes, each daughter cells will have 46 chromosomes in their nucleus.

Remember: duplication, condensed, alignment, pull apart.

2. Mitosis - remember "TOE," bc it's a skin cell, a non-sex cell. All non-sex cells in the body are called SOMATIC.

3. Diploid = 2n; it also means chromosomes in pairs, bc 2 sets came together initially at fertilization; 1 set (23 chromosomes) from male, 1 set (23 chromosomes) from female.
The single unpaired (single) chromosomes in sex cells find their counterpart at fertilization; hence you received 50% of your
chromosomes from each parent.

4. Haploid (monoploid) = unpaired or single chromosomes = n
Where a set = n; this means the chromosomes within sex cells are single, & in sex cells; eg: 1a, 2a, 3b, 4a...are all singles.

5. Diploid number is not achieved until 2 sex cells merge at fertilization; n + n = 2n ...means chromosomes are now paired;
eg: 1a +1b, 2a + 2b

6. Homologous chromosomes are paired chromosomes which carry genes for the same characteristics. eg: 1a,1b, or 3a,3b

7. Meiosis: crossing over occurs during Prophase I, before the metaphase I line-up.

Interphase - A cell may spend approximately 90% of it's life cycle in this phase.

HW. Please make sure you have reviewed the Mitosis-Meiosis T-chart which contrasts the 2 processes.
I would practice drawing them on BLANK paper, checking each stage when finished!


Can you draw the stages of MITOSIS using the 2n = 4 chromosomes; 1a,1b, 2a, 2b, 3a, 3b?
2. Can you demonstrate HOW the process of mitosis produces 2 exact copies (daughter cells).
3. Can you explain the concept of how meiosis produces different sex cells?

Questions. Comparing and Contrasting.

1. Which of the following is not a function of mitosis in humans?
a) repair of wounds
b) growth
c) production of gametes from 2n cells.
d) replacement of lost or damaged cells.

2) An intestinal cell in a dog contains 78 chromosomes; a dog sperm cell would contain _____ chromosomes.

3) A fruit fly somatic cell contains eight chromosomes. This means that _______ different combinations of
chromosomes are possible in it's gametes (sex cells = n).

4) A mule is the offspring of a horse and a donkey. A donkey sperm contains 31 chromosomes and a horse egg 32 chromosomes.
so the zygote contains a total of 63 chromosomes. The zygote develops normally. The combined set of chromosomes is not a problem
in mitosis, and the mule combines some of the best characteristics of horses and donkeys. However, a mule is sterile, meiosis cannot occur normally in it's testes or ovaries. Explain why mitosis is normal in cells containing both horse and donkey chromosomes but
the mixed set of chromosomes interferes with meiosis.

TBD - later
1. How are the growth of a malignant tumor (cancer) & the repair of a cut on your finger similar?
How are they different?

2. What's wrong with these statements? (Briefly explain why each statement is inaccurate or misleading).

a) The first stage of mitosis is the duplication of the chromosomes.
b) Every cell of a sexually reproducing organism has the same number of chromosomes.
c) Cells spend most of their time in the mitotic (M) phase of the cell cycle.

3. Why is it difficult to observe individual chromosomes during interphase?

4. Tumors that remain at their site of origin are called __________ ?
while tumors from which cells migrate to other body tissues are called ______________.

Honors- only.

1. A biochemist measures the amount of DNA in cells growing in the lab.
The quantity of DNA in a cell would be seen to DOUBLE:
a) between prophase and anaphase of mitosis
b) between the G1, and G2 phases of the cell cycle
c) during the M phase of the cell cycle.
d) between the prophase 1 and prophase II of meiosis.

2. A micrograph of a dividing cell from a mouse shows 19 chromosomes, each consisting of two sister chromatids.
During which stage of meiosis could this picture have been taken? Can you explain your answer?

Vocabulary - Please check your notes to make sure you can define and understand these terms.

chromatid -Well before cell division begins, each chromosome is replicated, or copied. Therefore, we see
2 identical “sister” chromatids held together with a belt; = 2 identical sister chromatids = 1 chromosome (already duplicated).
X shape = 2 duplicated single chromosomes tied together before the line up and division (pull apart).
Cell Division - see cytokinesis.
Chromatin: unwound, and functioning chromosomes.
Chromosome - I've drawn single chromosomes in "Interphase, not exactly) in order to demonstrate a starting point for mitosis
after interphase, into PMAT.
crossing over - eg: a couple on the beach, laying on a towel...when click...??
Cytokinesis - the division of a cell
diploid (2n) - cells where chromosomes are in pairs; 2 homologous sets of chromosomes; 1 from each parent.
fertilization - haploid (n) sperm fuses with haploid (n) egg; produces a zygote.
Gametes = sex cells - each sex cell has a single set of chromosomes; one from each homologous pair.
haploid (n) - 1 set of chromosomes. eg: eggs, sperm cells, unpaired chromosomes;
homologous chromosomes - used to refer to paired chromosomes; two (2) corresponding chromosomes from opposite sex parents, of each matching pair. 1a + 1b, 2a + 2b; contain genes related to the same genetic trait.
Interphase - approx 90% of a cell’s life cycle is spent in this phase. Cell carries out metabolic processes and performs its functions. eg: making and releasing enzymes, increases # of proteins, duplicates mitochondria, and ribosomes, grows in size. IPMAT -
karyotype- display of a person’s 46 chromosomes; all as sister chromatids (duplicated)
metaphase -line up of sister chromatids, preceding anaphase;
meiosis process - formation of sex cells; reduction division; where 2n produces cells which are n (single chromosomes)
mitosis first stage of cell division, that of division of the cell nucleus;
Mitosis -
nondisjunction- failure of sister chromatids to separate during anaphase. Good definition
reduction division - Process of producing hapoid (n) sex cells from diploid cells in testes and ovaries. Reducing the # of chromosomes by half.
Sister Chromatids- 2 identically duplicated chromosomes joined together; eg: 1a-1a, and appear as an X or )(
somatic cells - any non sex cell; 2n (diploid)
Spindle fibers -framework of microtubles - used for ??
tetrads - paired chromosomes in prophase 1, consisting of four chromatids...side by side.
zygote =fertilized egg; has 2 homologous sets of chromosomes, one set from each parent.

haploid number
Diploid number
Pea: Plant
n = 7
2n = 14
n = 10
2n = 20
Fruit fly
n = 4
2n = 8
n = 39
2n = 78
n = 19
2n = 38
n = 39
2n = 78
n= 24
2n = 48
n = 24
2n = 48
n = 23
2n = 46


Mitosis DR pipecleaners

Meiosis DR pipecleaners

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