Transcript Meiosis Guided Notes

Meiosis Guided Notes
Ramshaw – Biology
Interphase…
• Interphase happens at the start of
_____________ as well as mitosis.
• Prior to prophase I, the cell goes through
the G1, S, and G2 phases of
________________.
Prophase I
(chapter 10)
• DNA coils into ___________
chromosomes, spindle fibers
appear, nucleus disappears.
• Every chromosome is paired
up next to its ______________
(the chromosome that is the
same size and shape).
• This is called _____________
and does not occur in mitosis.
Prophase I (cont.)
• Each pair of homologous
chromosomes is called a
______________.
• When chromosomes line
up next to each other,
“____________ ______”
occurs and they
exchange pieces of DNA.
• This is called _________
recombination.
Crossing over
Only one cross over is shown
but many occur per pair.
So why is Crossing Over SO
important?????
• Reasons why:
Review of Key Terms
• Homologue (Homologous Chromosomes):
• Synapsis
• Tetrad
• Crossing Over
Metaphase I
• _____________ line up in the
center of the cell next to each
other.
• Spindle fibers from one
centriole attach to the
centromere of one _________
chromosome then spindle
fibers from the opposite
centriole attach to the other
homologous _____________.
Anaphase I
• Each homologous
chromosome moves to the
_____________ pole.
• This __________ separation
of homologous chromosomes
is called ________________
assortment.
– It separates the chromosomes
you inherited from your mom
and dad and creates new
combinations of ________ on
each chromosome!
Telophase I
• Chromosomes reach the opposite ends
of the ______, new nuclei form in each
new cell, and spindle fibers __________.
• The new cells are ___________!
To review…
What are the major events in Meiosis I?…
• Prophase I:
• Metaphase I:
• Anaphase I:
• Telophase I:
NO INTERPHASE HERE
• There is no interphase between
_____________ 1 and ____________ 2.
This is very important because there is no
S phase!!! (no doubling of the ________!!!)
Start of Meiosis II
Prophase II
– Centrioles form and move
toward the __________
– The nuclear membrane
________________
Metaphase II
• __________ fibers
attach from the
centrioles to the
centromeres
• The __________
chromatids line up
along the cell equator
Anaphase II
• The centromeres
__________ and
sister chromatids
separate
• The cell starts to
______ apart
Telophase II – Cytokinesis
• The cell pulls
_____________ apart –
forming new nuclei, one
in each cell
• Cytokinesis reaches
completion, creating ___
haploid ____________
cells
These 4 haploid cells then create:
• ______________!
• If the organism going through meiosis is a
female, only ___ of the cells becomes the
egg, the others become “_______ Bodies”
and are dissolved by the body. This
process of making an egg is called
__________________.
• If the organism going through meiosis is a
male, _____ __ cells become spermatids
which mature in to sperm. This is called
_______________________.
Major events in Meiosis!
• The cell starts out by doubling the _____
in Interphase:
After S1 phase
(Sister chromatids)
Copy of Chromosome
(doubling the DNA)
A chromosome before
the S1 phase
Original
Chromosome
After Interphase is…
• Prophase I
• _____________ and crossing over occur
• Lets draw that out!
Then comes:
• Metaphase I – Homologous chromosomes
line up in the _________ of the cell next to
each other.
• Anaphase I – The __________ are pulled
apart, one to each side of the cell
• Telophase I – Two ___________ cells are
formed
Then the second part - Meiosis II
• Prophase II – Nucleus _______________
• Metaphase II – Chromosomes line up
_________ file down the middle of the cell
• Anaphase II – Sister chromatids are pulled
___________ towards opposite ends of
the cell
• Telophase II – 4 __________ cells are
formed