Mitosis and Meiosis Books

Mitosis and Meiosis Books
Today you will make a meiosis book. The front
cover will just have the title and your name.
Pages 1-2 Vocabulary
Page 3 Chromosome Structure
Page 4 Mitosis Table of Contents
Page 5 Interphase
Page 6-10 Phases of Mitosis and Cytokinesis
Page 11 Meiosis Table of Contents
Page 12 Interphase
Page 11-20 on Phases of Meiosis
Page 21 Cytokinesis
Page 22 Compare Mitosis and Meiosis
Meiosis
Cell division where one diploid cell (2n)
produces four haploid (n) cells called
sex cells or gametes
These cells have half the number of
chromosomes as a body cell of a parent
Meiosis vocabulary
What is a gamete?
Male and female sex cells; the sperm
and egg
What is the male gamete?
Sperm; has 23 chromosomes
What is the female gamete?
Egg; has 23 chromosomes
Meiosis vocabulary…
What is a zygote?
A fertilized egg – has a diploid number
(2n) of chromosomes
What is sexual reproduction?
The pattern of reproduction that involves
the production and fusion of haploid sex
cells
What is a diploid cell?
Cell containing two of each kind of
chromosome from the parent
Meiosis vocabulary…
What is a haploid cell?
Cell containing one of each kind of
chromosome from the parent
What is an allele?
Gene form for each variation of a trait of an
organism. Example: gene for height can
express tall or short
Homologous chromosomes:
Pairs of like chromosomes even though the
alleles may be different – so they are not
identical chromosomes – sibling variation
Duplicates Coils up into
chromosomes
itself
Chromatin
Interphase—period of cell growth and development
•DNA replication (copying) occurs during Interphase
•During Interphase the cell also grows, carries out
normal cell activities, replicates all other organelles
•The cell spends most of its life cycle in Interphase
Phases of Mitosis
Prophase
Metaphase
Anaphase
Telophase
Prophase
 Chromosomes coil
up
 Nuclear envelope
disappears
 Spindle fibers form
Metaphase—(Middle)
 Chromosomes line up
in middle of cell
 Spindle fibers connect
to chromosomes
Anaphase—(Apart)
 Chromosome
copies divide
 Spindle fibers pull
chromosomes to
opposite poles
Telophase—(Two)
 Chromosomes uncoil
 Nuclear envelopes
form
 2 new nuclei are
formed
 Spindle fibers
disappear
Cytokinesis — the division of the rest of the cell
(cytoplasm and organelles) after the nucleus
divides
In animal cells the cytoplasm
pinches in
In plant cells a cell plate forms
•After mitosis and cytokinesis, the cell returns to
Interphase to continue to grow and perform
regular cell activities
The Phases of Meiosis
Interphase
Meiosis I
Prophase I
Crossing
Over
Metaphase I
Anaphase I
Telophase I
Meiosis II
Prophase II
Metaphase II
Anaphase II
Telophase II
Interphase
Carries out metabolic activities of the cell
Replicates its chromosomes
Precedes meiosis 1
Prophase I
• Chromosomes coil up and spindle form
• Homologous chromosomes pair up and a
four-part structure called a tetrad
forms
During prophase I…
• Tightly wound tetrads get so close to
one another that the genetic material
from one homologous pair exchanges
with the other creating new
combinations of alleles in the genetic
code
• Nuclear membrane disappears
• Nucleolus disappears
What is crossing over?
Exchange of
genetic
material by
non-sister
chromatids
during
prophase I
Results in
new
combinations
of alleles
Metaphase I
• Tetrads line up at the equator
• Homologous chromosomes are lined up in
pairs along the midline or equator of the
cell
• Spindle fibers attach to the centromere
on each pair
• The pairs are not attached to each
other
Anaphase I
• Homologous chromosomes are separated
and pulled to opposite poles of the cell
• The centromeres do not split during this
phase
• Each new cell receives only one
chromosome from each homologous pair
Telophase I
•
•
•
•
Spindle breaks down
Chromosomes uncoil
Cytoplasm divided in 2
Each cell has half the genetic
information from the original cell
• Chromosomes are still doubled
containing two sister chromatid
• Nuclear membrane reforms
• Two diploid daughter cells formed
Meiosis II
Is there an interphase in Meiosis II?
No. Chromosomes do not replicate
The cells go directly from meiosis I to
meiosis II
Prophase II
• Spindle forms in each of
the two new cells
• Chromosomes are still
coiled as sister chromatids
• Nuclear membrane
disappears
• Nucleolus disappears
Metaphase II
• Chromosomes line up at
the equator of the cell
• Spindle fibers attach to
the centromeres
Anaphase II
• Centromeres split
• Spindle fibers
pull separated
chromatids to
opposite poles of
the cell
Telophase II
•
•
•
•
•
•
Spindle fibers disappear
Chromosomes uncoil
Nuclear membrane reforms
Nucleolus reforms
Cytoplasm divides
Each cell now has half the chromosomes
that its parents had
• Four daughter haploid cells are formed
What are the two divisions of
meiosis?
Meiosis I and Meiosis II
Meiosis I
When homologous chromosomes come
together and separate
Meiosis II
The division that results in 4 daughter
cells, each with half the chromosomes
present in the original cell
What is genetic recombination?
Genetic variation
due to crossing
over and random
assortment
How many ways can
the chromosomes
line up?
2
How do you find the total number
of different kinds of sperm and
egg that can be produced?
• Take the number of pairs and place it as
the exponent with a base of 2
• Example: in humans there are 23 pairs
of chromosomes
• For sperm: 223 = over 8 billion
• For egg: 223 = over 8 billion
What is the total when
fertilization occurs?
223 * 223 = 70 trillion zygotes are possible