Use the next two slides to fill in the
rectangle at the top of the notes
page. It says “meiosis in a nutshell”
and “why meiosis?”
Meiosis – in a nut shell
Write this: CELL DIVISION RESULTING IN 4 GENETICALLY DIFFERENT
DAUGHTER CELLS, CALLED GAMETES, EACH WITH 23 CHROMOSOMES
Why Meiosis?
• Meiosis
• To produce gametes (sex) cells
which are:
– Egg and Sperm cells
• Use the next two slides to fill in the 7 terms
that are listed in the data table.
• I have already given you the definition on the
notes page, you need to write the correct
terms in the blank on your notes.
• Terms are in blue font on the slide.
Terms Review…
• Haploid: (n) having a single set of chromosomes in the cell.
ex. Gametes; humans have 23 chromosomes in sex cells (egg
and sperm cells)
•Diploid: (2n) having two sets of homologous chromosome in
the cell. ex. Somatic (body) cells; humans have 23 pairs or 46
chromosomes in body cells
Human Karyotype
with 23 pairs of
homologous
chromosomes for a
diploid number of 46;
2n = 2(23) = 46
Terms Continued
• Homologous chromosomes – two sets of chromosome in a pair, with one
set coming from a male parent and the other set coming from the female
parent.
• Tetrad – pairing of homologous chromosomes during meiosis I,
and such pairing has 4 (tetra) chromatids. These chromatids
can then exchange genetic material.
• Crossing-over – process in which tetrad of homologous
chromosomes exchange portions of their chromatids, and thus
genetic material is exchanged; this occurs during Prophase I of meiosis.
• Gametes – sex cells; involved in sexual reproduction. Male gametes
are called sperm cells and female gametes are called egg cells; sperm
are produced in testes and egg are produced in ovaries by meiosis.
• The next slide should be used to fill in the box
that says “crossing over”
Crossing Over
• What is happening?Exchange of genetic material
between homologous chromosomes
• How does this affect the individual (offspring)? Creates
genetic variation
• The next four slides should be used to fill in
the box with the “a, b, c, d” listed sentences.
• You have to READ the sentences on “a, b, c, d”
in order to fill in the correct answers from the
questions on the next 4 slides. Pay attention.
Meiosis Review
1.
Is the beginning parent cell diploid or
haploid (2n or n)?
2. Are the resulting daughter cells diploid or
haploid
(2n or n)?
Diploid
haploid
More Meiosis Review
4
different
3. How many daughter cells are
produced?
4. Are the resulting daughter cells
different
from the
parent cell?
More Meiosis Review
different 5. Are the resulting daughter cells different from
each other?
46
23
6. How many chromosomes are in a
human parent cell?
7. How many chromosomes are in a
human daughter cell?
More Meiosis Review
8. What types of cells are
produced by meiosis?
Gametes, which are eggs and sperm
• The next two slides will help you complete the
data tables at the bottom of the notes page.
• Fill in the data table with a check or “x”
Mitosis vs. Meiosis
Event
Mitosis
Produces 4 cells
√
Produces 2 cells
√
√
New cells identical
New cells different
New cells have the same number
of chromosomes as parent
New cells have fewer
chromosomes than parent
Meiosis
√
√
√
Mitosis vs. Meiosis
Event
Beginning cells diploid (2n)
Beginning cells haploid (n)
Ending cells diploid (2n)
Ending cells haploid (n)
Mitosis
Meiosis
√
√
√
Produces egg and sperm
Produces body cells
√
√
√