Download Mitosis

DNA Terminology….
The Cell Cycle….
Mitosis and Meiosis…..
I. Chromosomes
A. DNA wrapped
around proteins
(histones) is a
nucleosome
B. Uncoiled,
threadlike DNA is
Chromatin
(non-dividing cell)
C. DNA called a
chromosome
in dividing
cells;
short, fat rods
D.Half of a doubled Chromosome
= a Chromatid
1.Contains two identical parts
2. Attach at a point called the
Centromere
E. Homologous Chromosomes
1. Occurs in pairs; same size and
shape
2. Structurally different from
all other pairs
3. Have the
same gene locations
chromatid
centromere
F. Gene
1. Distinct unit on a
chromosomes
2. Sequence of
nucleotides
Eye
Color
II. “N” Number = The number of
chromosomes a cell has
A. Diploid (2N)
1. Each species has a
characteristic number of
chromosomes
2. Cells with both
Common
chromosomes of every
Name
Buffalo
pair called somatic or
Cat
body cells
Cattle
a) 2N for humans = 46
Dog
Donkey
b) Ex: Crayfish (200)
Goat
fruit flies (4)
Horse
Genus and
Species
Diploid Number
Bison bison
60
Felis catus
38
Bos taurus, B.
indicus
60
Canis familiaris
78
E. asinus
62
Capra hircus
60
Equus caballus
64
Human
Homo sapiens
46
Pig
Sus scrofa
38
Sheep
Ovis aries
54
B. Haploid (1N)
1. Cell with 1
chromosome of each
pair
2. Sex cell (sperm or
egg)-Gametes
III. Asexual and Sexual Reproduction
A. Mitosis is Asexual
1. Functions include
a) Unicellular Organism =
Reproduction
b) Multi-cellular Organisms
1) Growth and development from
egg
2) Replacement of dead or
damaged cells
c) Passes along the genome (total
DNA per species)
2. Each daughter cell is clone of
parent.
B. Meiosis is Sexual
1. Mixes DNA
2. Produces ½ the
number of the
chromosomes of
the parents
3. Cells involved in
sexual
reproduction
are sperm and
eggs (gametes)
IV. Cell Division
A.Prokaryotes: Called Binary Fission
B.Eukaryotes: Use the Cell Cycle
1.Interphase
2.Mitosis
3.Cytokinesis
V. Cell Cycle
sequence of growth
and division in the life of
a cell
=
G1
(growth;Gap 1)
11 hrs.
•Rapid cell growth
•Cell doubles in size
•Enzymes + organelles
double in number
S=Synthesis
•Growth
•DNA makes a copy
of itself
G2=Gap 2
7 hrs.
•Rapid Growth
•Final preparation
for cell division
3 hrs.
Cell Cycle =
Interphase = period of cell growth and
duplication of the DNA
G1 + S + G2
Mitosis = division of the cell’s nucleus
in which the chromosomes in the
parent cell divides into 2 identical
sets
Cytokinesis = cytoplasm divides in 2
daughter cells
VI. Stages of Mitosis
Prophase
a) Early Prophase
1)Chromatin coils to chromosomes
2)Nucleolus & nuclear membrane
break down & disappear
3)Centrioles move to poles (animal
cells only).
b) Middle Prophase
1) Spindle fibers
(microtubules) appear
2) Polar – centriole to
centriole
3) Kinetochore –
centromere to centriole
c) Late Prophase
1)Aster appear
(centriole and fibers)
2) Chromosomes
position is random
Metaphase
a) Kinetochore fibers
move chromosomes
b) Chromosomes line up
along equator
Anaphase
a) Centromere splits
b) Sister chromatids
pulled to opposite
ends
Telophase
a) Identical chromatids at
opposite end
b) Chromatids unwind &
elongate to chromatin
c) Centrioles & spindle
disappear
d) Nucleolus & nuclear
membrane reappear
1.Prophase
2.Metaphase
3.Anaphase
4.Telophase
C. Cytokinesis
1. Animal cells form cleavage
furrows
2. Plant cells form a cell plate
VII. Reproduction and Meiosis
A. Meiosis in males ♂
1. Part of
spermatogenesis
2. Occurs in the
testes
3. Always results in
four sperm cells
B. Meiosis in females ♀
1. Part of oogenesis
2. Occurs in the ovaries
3. One cell receives
most of the cytoplasm;
the other 3 cells are
polar bodies
4. Results in mature egg
( with 23 chromosomes)
VIII. Significance of Meiosis
A.
B.
Produces genetic variation
Without meiosis,
chromosome numbers would
continually increase
(teenage mutant Ninja turtles)
Common
Name
Genus and
Species
Diploid
Number
Buffalo
Bison bison
60
Cat
Felis catus
38
Cattle
Bos taurus, B.
indicus
60
Dog
Canis familiaris
78
Donkey
E. asinus
62
Goat
Capra hircus
60
Horse
Equus caballus
64
Human
Homo sapiens
46
Pig
Sus scrofa
38
Sheep
Ovis aries
54
IX. Review “N” Number
Mitosis => results in 2N
animals (1N)
Meiosis => results in 1N
plants (1N)
egg and sperm
(gametes)
spores and seeds
fuse
(2N zygote)
*♂ - sperm all viable after spermatogenesis
*♀ - after oogenesis, 1 egg(ootid) and 3 polar
bodies (no cytoplasm, just DNA)
X. Steps of Meiosis
(2 Separate Divisions)
Meiosis vs Mitosis
Meiosis I (starts with 2N)
Prophase I
 Chromatin shortens and coils to chromosomes
 Spindle appears
 Nucleolus and nuclear membrane disappear
 Unique step:
– Chromosomes line up next to their homologs
(called synapsis)
– Homolog pairs twist tightly to form a tetrad
– (4 chromatids that make up two doubled
chromosomes)
– Crossing over can occur; exchange of DNA
between homologs and/or 2 sister
chromatids
Tetrad Formation
Tetrad Formation
Meiosis I
Metaphase I
 Tetrads move to the equator;
homolog pairs stay together
Anaphase I
 Homologous pairs separate and
move to each pole ( one
chromosome of each pair pulled to
pole)
 2 chromatids still joined at
centromere
Meiosis I
Telophase I
 Cytoplasm divides forming 2
daughter cells
Meiosis II (chromosomes do not
double; ends with 4 (1n) cells
Prophase II
 New spindle forms
 Nuclear membrane and nucleolus
break apart
 Chromatin shortens and becomes
visible as sister chromatids
Metaphase II
 Sister chromatids move to the
equator
Meiosis II
Anapahse II
 Centromere divides; sister
chromatids move to opposite poles
Telophase II
 Nuclear membrane reforms; Spindle
disappears
 Cytokinesis occurs
 4 daughter cells from one parent