Download meiosis

• MITOSIS: cell division that
produces 2 daughter cells
identical to the parent cell
• MEIOSIS: cell division that
produces 4 daughter cells
with half the number of
chromosomes as the
parent cell = sex cells
Cellular Reproduction
• Interphase
• Most of cell life spent
here
• CHROMOSOMES
replicate and attach at
CENTROMERE
• Nuclear membrane still
present
• Centrioles Replicate

Prophase



Chromosomes
condense
Nuclear membrane
disappears
Spindle fibers form
between centrioles

Metaphase


Chromosomes line up
in the Middle
(equator) of the cell
They are connected
to the spindle fibers

Anaphase


chromosome splits at
each centromere
Chromosomes move
to opposite poles of
the cell

Telophase




Return to interphase
conditions
Nuclear membrane
forms
CYTOKENESIS =
division of remaining
cell parts
2 identical daughter
cells are formed
•
Chromosomes replicate (copy) during this
phase…
A.
B.
C.
D.
E.
ANAPHASE
INTERPHASE
METAPHASE
PROPHASE
TELOPHASE
•
The nuclear membrane disappears in this
phase…
A.
B.
C.
D.
E.
ANAPHASE
INTERPHASE
METAPHASE
PROPHASE
TELOPHASE
•
During this stage the nuclear membrane is
formed around the chromosomes…
A.
B.
C.
D.
E.
ANAPHASE
INTERPHASE
METAPHASE
PROPHASE
TELOPHASE
•
Chromosomes line up in the middle of the cell
and connect to the spindle fibers…
A.
B.
C.
D.
E.
ANAPHASE
INTERPHASE
METAPHASE
PROPHASE
TELOPHASE
•
Most cell life is spent in this stage…
A.
B.
C.
D.
E.
ANAPHASE
INTERPHASE
METAPHASE
PROPHASE
TELOPHASE
•
During this stage the chromosome split at
each centromere…
A.
B.
C.
D.
E.
ANAPHASE
INTERPHASE
METAPHASE
PROPHASE
TELOPHASE
•
Chromosomes condense and appear in this
phase…
A.
B.
C.
D.
E.
ANAPHASE
INTERPHASE
METAPHASE
PROPHASE
TELOPHASE
•
During this stage the chromosomes move to
opposite poles…
A.
B.
C.
D.
E.
ANAPHASE
INTERPHASE
METAPHASE
PROPHASE
TELOPHASE
•
During this stage 2 identical daughter cells
are formed…
A.
B.
C.
D.
E.
ANAPHASE
INTERPHASE
METAPHASE
PROPHASE
TELOPHASE

How Mitosis leads to growth and repair






Your growth
Root and shoot growth at tips in plants
Replacement of skin and stomach cells
Blood cell replacement
Repairing injury to your skin
Plant repair
• Reproduction by one parent cell
• Identical offspring
• Read pages 56-57 to find examples of
organisms that reproduce this way
• Yeast
• Bacteria
• Hydra
• Potatoes
• Sea Star
• Sexual Reproduction = reproduction by two
parents
• Results in SEX CELLS = egg or sperm
• Sex cells have ½ the number of chromosomes as the
parent cell
• Why is that important?
•
•
•
•
Meiosis-1 twin chromosomes separate = 2 cells
Meiosis-2 chromosomes split apart = 4 cells
Human cell has 46 chromosomes
Human sex cell has ??
• 23
• Fertilization = joining of sperm and egg
• Equals a ZYGOTE
• Look at picture on 66
• Grows by MITOSIS
• Offspring not identical to parent
 Asexual=
an exact copy
of the cell
• Sexual =
a cell with ½
of the original
chromosome
number
• In which of the following is the offspring
an exact copy of the parent cell…
A. Meiosis
B. Mitosis
•
In which of the following is the offspring a sex cell with ½ the
number of chromosome…
A.
B.
Meiosis
Mitosis
Mitosis
•Offspring
cell has
chromosomes
identical to
parent
•Begin with
parent cell
Meiosis
•Chromosomes
copied
•Chromosomes
separate
•Cell divides in
two
•Cell divides in
two again
•Offspring
cells have half
the
chromosomes
of parent
• In a few paragraphs, explain to me
the process of meiosis.


Their discovery
has allowed us to
understand how
the structure of
DNA makes it able
to copy itself
How TRAITS are
passed from parent
to offspring





Twisted ladder
Rungs = Molecule
Bases A,T,C,G
Sides = Sugar and
Phosphate
DNA found on
chromosomes
Contains info.
About organisms
traits



Chromosomes are
long strands of
DNA
Genes are sections
of DNA on a
chromosome that
controls a trait
Direct the building
of proteins that
make up your cells
Unzips like a
zipper into 2
halves
 Free floating
bases in the
nucleus attach to
the unzipped
DNA to make a
new ladder





GOAL = locate all genes on the
46 human chromosomes
Map the sequence of all base
pairs
GENOME = complete set of
genetic instructions for an
organism
At least 100,000 genes
organized to 46 chromosomes
(3 billion+ base pairs)



WHY?
Detect and treat genetic
disorders
 Cystic fibrosis
 MD
 Cancers
Identity of a person
 DNA from blood, hair,
skin
 GENETIC
FINGERPRINT
Mom’s Chromosomes(23) +Dad’s Chromosomes(23)
Genes on chromosomes for different traits
Like chromosome pairs line up
=
Zygote with 46 chromosomes
acting together to produce traits
• Dominant gene that will show up if present
• Recessive gene is “weaker”
• Will only show if person has two copies of this gene
•Pass the Genes, Please
• A change that occurs
when DNA copies
itself
• A mistake in the
copying process
• In a sex cell this is
passed on to
offspring