Download Meiosis II

Unit 6: MEIOSIS
Period: __
 _______________________ are special cells used in sexual reproduction.
 These cells contain _________ the normal # of chromosomes than the regular body cells.
When the sperm and egg unite the ________________ will contain the normal # of chromosomes for
that organism
Cell Division
Cell Type
# of daughter cells
# of chromosomes
4
46
Diploid
Mitosis
Gamete (sex)
•Meiosis reduces the number of chromosomes to ½ the # in body cells.
•This is called the _________________ number (4623)
•_____________________________ is necessary so that when
reproduction occurs =
 ______________________ contains the necessary 46
chromosomes
Egg (23 chromosomes) + sperm (23 chromosomes) = zygote (46 chromosomes)
Haploid
2 Divisions of Meiosis
There are _________ divisions of meiosis:
•Meiosis I and Meiosis II
•Must be in order to end up with:
•Each sex cell contains =
______________________________
Meiosis I
During the first meiotic division, chromosomes are __________________.
1. Prophase I chromatin makes a copy of itself
 begins to coil up
Crossing over occurs which is the exchange of chromosome
segments between _______________ ________________.
Crossing over during Prophase I
2. Metaphase I• ___________________ pairs of chromosomes line up together at the
middle of the cell.
• This forms a
_____________________
(meaning 4).
*H
Homologous chromosomes are _________________
chromosomes.
*Each contains ________________ for the same
trait.
3. Anaphase I•Homologous chromosomes that form each tetrad separate and
move to opposite ends.
•The ______________________________ (hold chromatids
together) do not split.
4. Telophase I•Spindle fibers disappear
•Cell divides by: ________________________ (a cleavage forms)
Meiosis II
During the second meiotic division ________________ is replicated.
1. Prophase II•centrioles double
•spindle forms
2. Metaphase II•chromosomes line up at the __________________
3. Anaphase II•Individual _____________________ move to opposite ends
4. Telophase II•________________________ cells divide into ______
new, unique daughter cells
•Each new daughter cell has 23 chromosomes.
•This is ½ the # of the original parent cell.
Where Does Meiosis Occur?
Testes of the male:
– Called ______________________; 4 sperm are produced.
Ovaries of the female:
– Called ______________________; 4 eggs are produced
•Only 1 becomes an egg used for reproduction!!!; Other ____________________
Meiosis I in Motion
I- ____________________________________________________________________
P1- centrioles move to opposite sides of cell
M1- ___________________________________________________________________
A1- chromosomes (intact) pulled to opposite sides by spindle fibers
T1- ___________________________________________________________________
Meiosis II in Motion
P2- ___________________________________________________________________
M2- 2 chromosomes line up in middle
A2- ___________________________________________________________________
T2- cell splits forming 4 daughter cells that contain haploid set of chromosomes