Cell Division Study Guide
1. Draw and label the cell cycle.
2. What is happening to the cell during
interphase? (see below)
3. Draw a picture of a replicated chromosome (see chromosome on
right).
4. Draw a picture of a non-replicated chromosome (see left).
Non-replicated
Replicated
Sister chromatids
5. What does diploid mean? What type of cell
in your body is diploid?
•
A cell that contains both sets of homologous chromosomes is said to
be diploid, which means “two sets”. The number of chromosomes in a
diploid cell is sometimes represented by the symbol 2N.
•
For Drosophila (fruit fly), the diploid number is 8, which can be
written 2N = 8.
•
All cells EXCEPT sex cells are diploid. These are called somatic cells.
6. What do you call each pair of chromosomes in a
diploid cell? Is each chromosome similar or identical?
• A pair of chromosomes in a
diploid cell are called
HOMOLOGOUS.
• One member of the homologous
pair comes from your Mom – the
other comes from Dad. They are
not identical, but they DO carry
similar sequences of DNA!
7. What does haploid mean? What type of cell in your
body is haploid? What are two examples of gametes?
• Haploid means “one set”. For Drosophila
(fruit fly), this can be written as N = 4.
• Haploid cells in the body include gametes,
or sex cells. Two examples: sperm cells
(males) and egg cells (females).
8. What type of cell undergoes meiosis to produce
gametes? Where are these cells found?
• Sperm producing cells
in males are found in
the testes.
• Egg producing cells in
females are found in the
ovaries.
• Both of these cells
undergo meiosis in
order to produce
haploid (N) egg and
sperm cells.
9. Define mitosis. List the 4 phases of mitosis.
Reproduction by mitosis is
classified as asexual, since the
cells produced by mitosis are
genetically identical to the
parent cell. Mitosis is also a
source of new cells when a
multicellular organism grows and
develops.
10. If the diploid number of replicated
chromosomes is 24, how many chromosomes
would you find in the egg cell of this animal?
• Answer: 12
11. If the diploid number of replicated
chromosomes is 24, how many chromatids would
there be? How many centromeres?
• Answer: 48 chromatids, 24 centromeres
12. In meiosis, the parent cell (germ cell) has
a diploid number of chromosomes, and the
resulting daughter cells have a ________
number of chromosomes.
• haploid
13. What is separating in meiosis I?
• Homologous chromosomes (replicated).
Draw the diagrams.
• For questions 13 – 16, use your textbook, pg.
276-277 to draw the chromosomes during
meiosis I.
17. What is separating in meiosis II?
• The 2 cells produced by meiosis I now enter a second
meiotic division. Unlike the first division, neither cell
goes through a round of replication before entering
meiosis II.
• Each of the cell’s chromosomes has 2 chromatids.
During metaphase II, chromosomes line up in the
center of the cell. In anaphase, the paired
chromatids separate.
18. When a sperm (1N) fertilizes an egg (1N), what is the
chromosome number of the resulting zygote (haploid or
diploid)?
• Answer: Diploid (2N)
19. How many chromosomes do humans have in a somatic
cell? In a gamete/sex cell?
• Answer: Somatic cell: 46 chromosomes, Gamete: 23 chromosomes.
20. Fill in chart:
MITOSIS
MEIOSIS
Chromosome # of
parent cell
# of daughter cells
diploid
diploid
2
4
Chromosome # of
daughter cells
Genetic content of
daughter cell
diploid
haploid
identical
variable
Compare mitosis & meiosis.
21. What is spermatogenesis? How many sperm are
produced from each germ cell?
• Production of sperm cells. Number of sperm produced: 4
22. What is oogenesis? How many eggs are
produced from each germ cell?
• Production of egg cells. Number of eggs produced: 1
Compare spermatogenesis & oogenesis:
23. What is nondisjunction? List and describe 3 chromosomal
disorders caused by nondisjunction.
• Nondisjunction is when homologous chromosomes fail to
separate.
• Three examples:
• Down’s syndrome (trisomy 21) or 3 copies of chromosome 21.
• Kleinfelter’s syndrome (males): sex chromosomes are XXY, instead
of XY.
• Turner’s syndrome (females): sex chromosome is X-, instead of
XX.
Chromosomal disorders
Down’s syndrome
Trisomy-21
Kleinfelter’s
syndrome
XXY
Turner’s syndrome
XO
24. How does meiosis cause genetic variation?
• As homologous chromosomes pair up and form tetrads in
meiosis I, they exchange portions of their chromatids in a
process called crossing-over. Crossing-over produces
variability in the 4 haploid chromosomes produced at the
end of meiosis.