Download Meiosis PPT

How do
we make
these?
Videohttps://www.youtube.com/watch?v=toWK0fIyFlY
Meiosis
• Involved in _____________________
reproduction.
•
• Process by which chromosome number
is divided in _________________ in order
to produce
__________________________
(Sex
cells: egg/sperm)
***Before looking at Meiosis you
need to understand chromosome
number.
***
• Let’s consider the fruit fly which has _______ chromosomes
•
• 4 came from _____________ parent and 4 came from
_________________ parent: These two sets of chromosomes
are _____________________ CHROMOSOMES, meaning that
each of the 4 chromosomes from the male parent has a
corresponding chromosome from the female parent.
• A cell that contains both sets of homologous
chromosomes is said to be ________________,
which means two sets. Diploid is represented as
________.
•
• The gametes (sex cells) contain only a single set of
chromosomes and are said to be ________, which
means one set. Haploid is represented by ______.
•
•  So what is the diploid number of chromosomes
for a fruit fly? ______ Haploid number? _____
•
Okay back to Meiosis
• Meiosis involves _______ distinct divisions, called MEIOSIS I and
MEIOSIS II.
•
•  By the end of meiosis II, the ______________ cell that entered
meiosis will become ______ haploid cells.
•
• The Process of Meiosis
• _______________________: Meiosis is preceded by an Interphase
• Chromosomes replicate
• G1, S, G2 (same as Mitosis)
Meiosis I
• (separates _________________ chromosomes)
Prophase I:
• Each chromosome pairs with its corresponding
homologous chromosome to form a ____________.
There are _____ chromatids in a tetrad.
• __________________________ occurs, where
homologous chromosomes exchange segments.
•
Metaphase I
• Spindle fibers attach to chromosomes.
• Chromosomes line up along the middle of the
cell.
Anaphase I:
• Spindle fibers pull the homologous chromosomes toward
opposite ends of the cell
Telophase I and Cytokinesis:
• Nuclear membranes form.
• Cell divides into ______ cells.
Meiosis II
• separates _____________________
Prophase II
• Spindle apparatus forms in the two haploid cells
Metaphase II:
• Chromosomes line up along the middle of the
cell
Anaphase II:
• Sister chromatids separate and move toward
opposite ends of the cell
Telophase II and Cytokinesis
• a.
• b.
Nuclear membranes form.
Cell divides into _____ haploid daughter cells.
Comparing Mitosis & Meiosis
Characteristic
No Pairing of Homologs Occurs
Two Divisions
Four Daughter Cells Produced
Associated with Growth &
Asexual Reproduction
One Division
Two Daughter Cells
Produced
Involves Duplication of
Chromosomes
Chromosome Number is
Maintained
Chromosome Number is
Halved
Crossing Over Between
Homologous Chromosomes
May Occur
Daughter Cells Are Identical
to Parent Cells
Daughter Cells Are Not
Identical to Parent Cells
Produces Gametes
Synapsis Occurs in
Prophase
Mitosis
Meiosis
Cells alive WS