Transcript Review MEIOSIS – the process of cell division in which - Room N-60

The Process
ESLR: To become critical thinkers
STANDARD: Students know
meiosis is an early step in sexual
reproduction in which the pairs of
chromosomes separate and
segregate randomly during cell
division to produce gametes
containing one chromosome of
each type.
Review
MEIOSIS – the process of cell
division in which the number of
chromosomes are reduced to half
through a process of separating
homologous pairs.
Review
MEIOSIS – the process of cell
division in which the number of
chromosomes are reduced to half
through a process of separating
homologous pairs.
Diploid –
Haploid -
Review
MEIOSIS – the process of cell
division in which the number of
chromosomes are reduced to half
through a process of separating
homologous pairs.
Diploid – 2 copies of each chromosome
Haploid - 1 copies of each chromosome
Meiosis
A cell division forming haploid cells
Goal: reduce genetic material by half
Why?
from mom
from dad
child
too
much!
meiosis reduces genetic content
Phase: Interphase
Cells grow and
undergo a round
of DNA replication
forming duplicate
chromosomes
Nucleus
MEIOSIS 1
Phase: Prophase 1
Each chromosome
pairs with its
corresponding
homologous
chromosome –
(homolog) to form a
tetrad (4 chromatids)
MEIOSIS 1
Phase: Prophase 1
A
A
B
C
a
b
c
D D
d
B
C
E
F
E
F
e
f
a
b
c
d
e
f
They exchange
parts of
chromosomes –
Crossing Over
MEIOSIS 1
A
a
B
C
C
c
D D
E
F
b
c
d
E
F
e
f
Phase: Prophase 1
Crossing over
d
e
f
MEIOSIS 1
a
A
B
b
C
C
B
c
D D
E
F
a
A
d
E
F
e
f
b
c
Phase: Prophase 1
Crossing over
•Generates diversity
d
e
f
MEIOSIS 1
Phase: Metaphase 1
Spindle fibers attach
to the chromosomes
Spindle
fibers
MEIOSIS 1
Phase: Anaphase 1
Fibers pull the
homologous
chromosomes
toward the opposite
ends of the cell
MEIOSIS 1
Phase: Telophase 1
& Cytokinesis
Nuclear
envelope
Nuclear membrane
forms and the cell
separates into two
cells
MEIOSIS II
Phase: Prophase II
MEIOSIS II
Phase: Metaphase II
Chromosomes line
up across the center
of the cell similar to
mitosis
MEIOSIS II
Phase: Anaphase II
Sister chromatids
separate and move
toward the opposite
ends of the cell
MEIOSIS II
Phase: Telophase II
Nuclear membranes
Chromosomes uncoil
Spindles disappear
MEIOSIS II
Phase: Cytokinesis
Four haploid cells
One copy of each
chromosome