Transcript Mitosis

Cell Divisions
Mitosis and Meiosis
Mitosis
• Division of the nucleus of all
cells except sex cells
• Produces 2 daughter cells each
with the same amount and type
of genetic material as the parent
cell
Synthesis
• Also called Interphase of the cell
cycle
• Not technically part of Mitosis
• DNA is replicated (copied) to
make an exact copy of itself
• Each “new” strand is 1/2 of the
“old” strand and 1/2 of newly
formed strand
Prophase
• 1st stage of
Mitosis
• Nuclear
membrane
begins to
weaken
Prophase
• Centrioles
(Protein
structures) form
and move to the
poles of the
nucleus
Metaphase
• Chromosomes
line up in the
middle
• Spindle fibers
extend from the
centrioles to the
centromeres
Anaphase
• Spindle fibers
shorten
• Chromosomes
are pulled
apart at the
centromere
• Chromatids
move to the
opposite sides
Telophase
• Nuclear
membranes begin
to reform
• Spindle fibers are
gone
• Centrioles begin to
disassemble
• Cleavage forms
– Cleavage - an
indentation in
tissue
Cytokinesis
• Nuclear
membrane
complete
• New cell
membrane
forms at
cleavage
• Exact copy of
the original
cell
Cell Division
for Sex Cells
Meiosis
• Division of the nucleus of sex
cells
• Produces 4 daughter cells each
with the 1/2 amount and type of
genetic material as the parent
cell
Meiosis
• The first 1/2 is identical to
Mitosis
• Before the 2nd 1/2 the DNA is
NOT replicated
Prophase 1 of Meiosis
• Nuclear membrane
begins to dissolve
• Centrioles begin to
Quic kTime ™ and a
or
form and move to are n eededed compress
to s ee th is p ictu re.
the poles
Metaphase 1 of Meiosis
• Chromosomes
line up in the
middle
QuickTim e™ and a
decom pressor
are needed to see this picture. • Spindle fibers
extend from the
centrioles to the
centromeres
Anaphase 1 of Meiosis
• Spindle fibers
shorten
• Chromosomes
are pulled
Quic kTime ™ and a
apart at the
de compress or
centromere are n eede d to see th is pict ure.
• Chromatids
move to the
opposite sides
Telophase 1 of Meiosis
Quic kTime ™ and a
de compress or
are n eede d to see t his pict ure.
• Nuclear
membranes
begin to reform
• Spindle fibers
are gone
• Centrioles begin
to disassemble
• Cleavage forms
Cytokinesis 1 of Meiosis
• Nuclear
membrane
complete
• New cell
membrane
forms at
cleavage
• Exact copy of
the original
cell
Quic kTime ™ and a
de compress or
are n eede d to see t his pict ure.
Metaphase 2 of Meiosis
Quic kTime ™ and a
de compress or
are n eede d to see th is pict ure.
• Single copy of
the
chromosomes
line up in the
middle
• Spindle fibers
extend from the
centrioles to the
centromeres
Anaphase 2 of Meiosis
• Spindle fibers
shorten
• Single
Chromosome is
pulled apart at
the centromere
• Chromatids
move to the
opposite sides
QuickTim e™ and a
decom pressor
are needed to see this pi cture.
Telophase 2 of Meiosis
QuickTim e™ and a
decom pressor
are needed to see this picture.
• Nuclear
membranes begin
to reform
• Spindle fibers are
gone
• Centrioles begin to
disassemble
• Cleavage forms on
4 new cells
Cytokinesis 2 of Meiosis
• Nuclear
membranes
complete
• New cell
membranes
form at
cleavage
• 4 cells each
with 1/2 the
genetic
information of
the parent cell
QuickT ime™ and a
decompressor
are needed to see this picture.
Mutations
Mutations
• Mutation:
– Any change in the sequence
(order) of the DNA
• 3 main types
– Insertion
– Deletion
– Substitution
Results of Mutations
• Benign - not good/not bad
– This type of mutation leads to
variations of traits
• Different hair color, skin color, etc
• Helpful
– This type of mutation is beneficial
to the organism
• Harmful
– This type of mutation interferes
with normal protein production and
often leads to illness or death
Variation
• A change in a trait which is
caused by a change in the DNA
Insertion Mutation
• If the DNA were a sentence like:
My sister is Betty
Insertion would add 1 or more letters
to the sentence:
My sisters is Betty
Bad grammar, but the sentence still
makes sense
Deletion Mutation
• Using the same sentence:
• My sister is Betty
• Deletion mutation removes one or
more letters
• My sister is Btty
• This can still makes sense, but
changes the meaning of the sentence
which in a cell could change the
protein
Problems with Insertion and
Deletion Mutations
• Once the message is carried out of
the nucleus by RNA (we have not
talked about this) all messages are
read in 3 base segments
• Adding or removing 1 base causes
these segments to be completely
changed
Insertion and Deletion
Continued
• Using our sentence the 3 base
sequences would look like this:
• MYS IST ERI SBE TTY
• Insertion would cause this:
• MYS IST ERS ISB ETT Y
• Deletion would cause this:
• MYS IST ERI BTT Y
Substitution Mutation
• Still using the same sentence:
• My sister is pretty
• Substitution changes one or
more letters
• My mister is pretty