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3/22/2016
TYPES OF REPRODUCTION
Cellular
Reproduction
• Asexual
– Relies on MITOSIS
– All of the parent’s DNA goes to the
offspring
• Sexual
– Relies on MEIOSIS
– Used to create sex cells
TYPES OF CELLS
• Body Cells
TYPES OF CELLS
• Sex Cells
– Includes all cells that are not sex cells
• i.e. skin, liver, muscle, etc…
– Also called somatic cells (soma- means
“body”)
– Made by MITOSIS
– Contain 2 copies of each chromosome
– Include egg cells and sperm cells
– Also called gametes
– Made by MEIOSIS
– Contain 1 copies of each chromosome
• Have a haploid # (n)
– Ex. Humans = 23
• Called homologous chromosomes
• Have a diploid # (2n)
– Ex. Humans = 46
Chromosome Numbers
Egg
Sperm
(haploid # of 23)
(haploid # of 23)
Genetic Material
• During most of the cell’s life,
genetic material exists in
chromatin
– Genetic material (DNA or RNA)
that is long and tangled
Fertilization
Zygote
(diploid # of 46)
• Chromatin coils up (during M
phase) to form chromosomes
• When UNCOILED, chromatin
makes RNA and can replicate
itself… When COILED, cell
division can occur
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Anatomy of a Chromosome
The Cell Cycle
The sequence of growth and division of a cell
• Cells go through THREE (3) periods
– One of growth
– One of nuclear division
– One of cytoplasmic division
The Cell Cycle
The sequence of growth and division of a cell
• The growth period is called INTERPHASE
– the stage during which the cell grows, carries out cellular
functions, and replicates its DNA.
– Consists of Gap 1, Synthesis, & Gap 2
END
START
G0
RESTING
• The nuclear division period is called M PHASE
(Mitosis)
– the stage of the cell cycle during which the cell’s nucleus
and nuclear material divide.
– Consists of Prophase, Metaphase, Anaphase, and
Telophase
• The cytoplasmic division period is called
CYTOKINESIS
– the method by which a cell’s cytoplasm divides, creating
a new cell.
Stages of Interphase
GAP 1 (G1)
• The first stage of INTERPHASE
• The cell is growing, carrying out normal cell
functions and preparing to replicate its DNA.
Stages of Interphase
SYNTHESIS (S)
• The second stage of INTERPHASE
• The cell will copy its DNA in preparation for cell
division.
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Stages of Interphase
Stages of Mitosis
GAP 2 (G2)
• The third stage of INTERPHASE
• The cell grows more and prepares for division of its
nucleus.
Prophase
•
1st
stage of Mitosis
Mitosis
Rap
– During Prophase…
• Chromatin coils up into visible chromosomes
– Chromosomes are made up of two halves called
chromatids
– Chromosomes are held together by a centromere
• The nucleus (nuclear envelope) will disappear
during this phase
• Centrioles will begin to separate
Stages of Mitosis
Stages of Mitosis
Prophase
Metaphase
• 2nd stage of Mitosis
– During Metaphase…
•Spindle fibers pull the chromosomes to
the middle (equator/metaphase plate) of
the cell
– This is the shortest phase of Mitosis, but
the most recognizable.
Stages of Mitosis
Stages of Mitosis
Metaphase
Anaphase
• 3rd stage of Mitosis
– During Anaphase…
•Chromosomes will be pulled apart
forming chromatids.
•Once the chromatids are separated, they
will move towards opposite sides of the
cell.
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Stages of Mitosis
Stages of Mitosis
Anaphase
Telophase
•
4th
stage of Mitosis
– During Telophase…
• The chromatids uncoil, becoming chromatin
• The nuclear envelope reforms
• Mitosis is COMPLETE!!!
* NOTE: Telophase and Cytokinesis will
happen concurrently
Stages of Mitosis
Telophase
Cytokinesis
• Last stage in The Cell Cycle
– During Cytokinesis…
• The cytoplasm (and its contents) will divide into two new cells.
– ANIMAL CELLS
» The cell membrane will move inward creating a cleavage
furrow
» Then the cell will pinch apart
– PLANT CELLS
» A cell plate will begin forming at the center of the cell and
work its way out forming a cell wall division between the
two new cells.
* NOTE: Telophase and Cytokinesis will happen concurrently
CLEAVAGE FURROW
CLEAVAGE FURROW
Cell Cycle Animations
CELL PLATE
• Sumanas Inc. Mitosis Animation
• Cells Alive Cell Cycle Animation
• Step-wise Cell Cycle Animation
• McGraw-Hill Mitosis Animation
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DIPLOID (2n)
SOMATIC
HAPLOID (n)
GAMETES
Meiosis
• Produces Sex Cells
• Reduction division
19
HAPOLOID (n) GAMETES
19
+
19
2n
=
38
MITOSIS
– Starts with 1 diploid cell and ends up
with 4 haploid cells
• Occurs in TWO steps
– Meiosis I
– Meiosis II
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Interphase
Prophase I
• Pairing of homologous
chromosomes occurs
• Chromosomes replicate
• Chromatin condenses
– Each chromosome
consists of two
chromatids
• The nuclear envelope
breaks down
• Spindles form
Prophase I
Interphase
Homologous Chromosomes
• One of two paired
chromosomes, one
from each parent
• Same length
• Same centromere
position
• Carry genes that
control the same
inherited traits
Crossing Over
• The exchange of material between
homologues
– Occurs during Prophase I
– Tetrads are formed and DNA is exchanged
– Produces chromosomes that contain genes
from both parents… GENETIC DIVERSITY
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Metaphase I
Independent Assortment
• Chromosome
centromeres
attach to spindle
fibers
• Homologous
chromosomes
(tetrads) line up
at the equator
• The random distribution
of genes located on
different chromosomes.
• Since each homologous pair assorts
Metaphase I
DIPLOID (2n)
SOMATIC
independently from all others, the
process produces 2n possible
combinations of maternal and
paternal chromosomes in gametes
(where n is the haploid number)
• In humans, the possible combinations
would be 223, or eight million – there
are eight million possible assortments
of chromosomes from the parents
HAPLOID (n)
GAMETES
Anaphase I
19
HAPOLOID (n) GAMETES
19
+
19
2n
=
38
MITOSIS
38
219 = 524,288
• Homologous
chromosomes
separate and
spindle fibers move
them towards
opposite poles of
the cell
Anaphase I
Telophase I & Cytokinesis
Telophase I
• Spindles break down
• Chromosomes uncoil to form
two nuclei
• This second division separates sister
chromatids of each chromosome
(virtually identical to Mitosis)
Cytokinesis
• The cell divides into two
new daughter cells
 Each pole now has a diploid
set of chromosomes that are
still composed of two sister
chromatids attached at a
centromere
MEIOSIS II
Telophase I
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Prophase II
Metaphase II
• Spindle apparatus forms and
chromosomes condense
• A diploid number of chromosomes align
along the metaphase plate
Metaphase II
Prophase II
Anaphase II
Telophase II & Cytokinesis
Telophase II
• Chromosomes are pulled apart
producing sister chromatids.
– Each chromatid is pulled (by the
spindles) towards the opposite poles of
the cell
• Chromatids reach the poles
• Nuclear membranes and nuclei reform
Cytokinesis
• Results in four haploid cells, each with n number
of chromosomes.
Telophase II
Cytokinesis
Anaphase II
The Meiosis Square Dance
Gamete Development
in Males
• “SPERMATOGENESIS”
• Meiosis occurs in
testes at puberty and
then occurs as needed
• 1 spermatocyte = 4 sperm cells
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Gamete Development
in Females
HUMAN LIFE CYCLE
Uses both meiosis & mitosis
• “OOGENESIS”
• Meiosis occurs in
the ovaries before
birth
•
1 oocyte = 1 egg & 3 polar bodies
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