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Cell ReproductionChapter 9 &10
Biology 114
Developed By Adam F. Sprague
Ocean County College
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OBJECTIVES:
Describe the structure of a chromosome.
Compare prokaryotic chromosomes with
eukaryotic chromosomes. Explain thedifferences between sex chromosomes and
autosomes. Give examples of diploid and
haploid cells.
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CHROMOSOMES
DNA is a long thin
molecule that stores
Genetic Information.The DNA in a human
cell is estimated to
consist of six billion
pairs of nucleotides.
http://rds.yahoo.com/S=96062857/K=DNA/v=2/SID=e/l=II/R=7/SS=i/OID=dd6303a61a4ba0b8/SIG=1ia977hi1/EXP=1131197856/*-http%3A//images.search.yahoo.com/search/images/view?back=http%3A%2F%2Fimages.search.yahoo.com%2Fsearch%2Fimages%3Fp%3DDNA%26sm%3DYahoo%2521%2BSearch%26fr%3DFP-tab-img-t%26toggle%3D1%26cop%3D%26ei%3DUTF-8&h=480&w=435&imgcurl=www.lakemichigancollege.edu%2Fliberal%2Fbio%2Fpics%2FDNA.gif&imgurl=www.lakemichigancollege.edu%2Fliberal%2Fbio%2Fpics%2FDNA.gif&size=52.8kB&name=DNA.gif&rcurl=http%3A%2F%2Fwww.lmc.cc.mi.us%2Fliberal%2Fbio%2Fbio212%2Fgenetic.html&rurl=http%3A%2F%2Fwww.lmc.cc.mi.us%2Fliberal%2Fbio%2Fbio212%2Fgenetic.html&p=DNA&type=gif&no=7&tt=285,519&ei=UTF-8 -
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CHROMOSOME
STRUCTURE
1. During Cell Division, the DNA (CHROMATIN) in an Eukaryotic Cell's
Nucleus is coiled into very tight compact structures called CHROMOSOMES
2. Chromosomes are Rod Shaped structures made of DNA and Proteins.
3. The Chromosomes of stained Eukaryotic cells undergoing cell division arevisible as darkened structures inside the Nuclear Membrane.
4. The DNA in Eukaryotic cells wraps tightly around Proteins called
HISTONES. They help to maintain the shape of Chromosomes and aid in the
tight packing of DNA.
5. Proteins called NONHISTONEProteins Do Not participate in packing ofDNA, they are involved in Controlling the Activity of Specific Regions of the
DNA.
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CHROMOSOME
STRUCTURE
6. When preparing for Cell Division, Chromosomes form Copies of
themselves, Each half of the Chromosome is called a CHROMATID or
SISTER CHROMATIDS. Chromatids form as the DNA makes copies of
itself before cell division. (Figure 8-2)
7. The constricted area of each Chromatid is called a CENTROMERE. The
Centromere holds the Two Chromatids together until the separate during Cell
Division.
8. Between Cell Division, DNA IS NOT so Tightly Coiled into Chromosomes.
The Less tightly coiled DNA-Protein complex is called CHROMATIN.
9. Chromosomes are simpler in prokaryotes. The DNA of most Prokaryotes
comprises only ONE Chromosome, which is attached to the inside of the Cell
Membrane.
10. Prokaryotic Chromosomes consist of a circular DNA Molecule and
associated Proteins.
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CHROMOSOME NUMBERS
1. EACH HUMAN BODY CELL CONTAINS 46 CHROMOSOMES, (2n)
OR TWO COMPLETE SETS.
2. ANY CELL THAT CONTAINS TWO COMPLETE SETS OF
CHROMOSOMES IS CALLED A DIPLOID CELL. A Diploid Cell iscommonly abbreviated as 2n.
3. THE NUMBER OF CHROMOSOMES IN A DIPLOID CELL IS CALLED
THE DIPLOID NUMBER. EVERY ORGANISM HAS A
CHARACTERISTIC DIPLOID NUMBER (2n).
4. EXAMPLES: FRUIT FLIES - 8, LETTUCE - 14, GOLDFISH 94, ANDHUMANS 46.
5. A CELL WITH ONLY ONE COMPLETE SETOF CHROMOSOMES IS
CALLED A HAPLOID CELL.
A Haploid Cell is abbreviated as 1n.
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CHROMOSOME NUMBERS
6.GAMETES, EGGS AND SPERM CONTAIN ONLY ONE COMPLETE
SET. EACH HUMAN SPERM OR EGG (GAMETE) CONTAINS 23
CHROMOSOMES, THE HAPLOID NUMBER (1n) FOR ALL
HUMANS.
7. WHEN AN EGG AND A SPERM OF THE SAME TYPE OF ORGANISM
JOIN TO PRODUCE A NEW INDIVIDUAL, THE PROCESS IS CALLEDFERTILIZATION.
8. THE SINGLE CELL THAT RESULTS FROM FERTILIZATION IS
KNOWN AS A ZYGOTE.THE ZYGOTE CONTAINS TWO COMPLETE
SETS OF CHROMOSOMES, ONE SET FROM EACH GAMETE,
FORMING A DIPLOID CELL. IN MOST MULTICELLULARORGANISMS, THE ZYGOTE IS THE FIRST CELL OF THE NEW
INDIVIDUAL.
9. The Chromosomes in the Zygote exist in PAIRS. For every Chromosome
that was in the egg, there is a matching Chromosome from the sperm.
10. Human and Animal Chromosomes are categorized as eitherSEXCHROMOSOMES or AUTOSOMES.
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CHROMOSOME NUMBERS
11.SEX CHROMOSOMESare Chromosomes that Determine the SEX of an
Organism.
12. In Humans, Sex Chromosomes are either X or Y. Females have TWO X
Chromosomes and Males have an X and Y Chromosome. 13. All the Other Chromosomes in an Organism are called AUTOSOMES.
14. TWO of the 46 Human Chromosomes are Sex Chromosomes, while the
reaming 44 are Autosomes.
15. MATCH SET OF AUTOSOMES IN A DIPLOID CELL ARE CALLED
HOMOLOGOUS PAIRS. BOTH CHROMOSOMES IN A HOMOLOGOUSPAIR CONTAIN INFORMATION THAT CODE THE SAME TRAIT
(GENES). Example Eye Color.
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CELL DIVISION
CELL DIVISION IN PROKARYOTES
1. BINARY FISSIONis the Division of a
Prokaryotic cell INTO TWO Offspring
Cells.
2. Binary Fission consist of THREE
General Stages:
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THREE General Stages
STAGE 1- The Chromosome, which is
attached to the Inside of the Cell
Membrane, makes a COPY of Itself,
Resulting in Two Identical
Chromosomes Attached to the Inside ofthe Inner Cell Membrane.
STAGE 2- The Cell continues to grow
until it reaches approximately TWICE
its Normal Size. Then a CELL WALL
Begins forms between the Two
Chromosomes.
STAGE 3- The Cell SPLITS into
TWO NEW CELLS. Each New Cell
contains on the Identical Chromosomes.
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CELL DIVISION IN
EUKARYOTES
THE PHASES OF
LIFE OF A CELL
ARE CALLED THECELL CYCLE.
THE CELL CYCLE
CONSISTS OF
THREE PHASES:A. INTERPHASE
B. MITOSIS
C. CYTOKINESIS.
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MITOSIS
is a Series of PHASES in Cell Division
during which the NUCLEUS of a Cell
Divides into TWO NUCLEI WITHIDENTICAL GENETIC MATERIAL.
MITOSIS OCCURS ONLY IN
EUKARYOTES.
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INTERPHASE CONSIST OF
THREE PHASES:
A. G1 PHASE- PERIOD OF NORMAL METABOLIC CELLULAR
ACTIVITIES: THE NUMBER OF ORGANELLES AND AMOUNT OF
CYTOPLASM IN A CELL INCREASE. Offspring Cells Grow to Mature
Size.
B. S PHASE- THE GENETIC MATERIAL (DNA) IS DUPLICATED
(COPIED). THE CHROMOSOMES OF THE CELL REPLICATE.
C. G2 PHASE- Structure directly involved with mitosis are formed. The Cell
makes the Organelles and substances it needs for Cell Division. A time during
which the Cell prepares to divide.
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CELL DIVISION INVOLVES TWO
STEPS: CALLED MITOTIC CELL
DIVISION.
A. MITOSIS - FIRST STEP. A SERIES OF
PHASES IN CELL DIVISION DURING WHICH
THE NUCLEUS OF A CELL DIVIDES INTOTWO NUCLEI WITH IDENTICAL GENETIC
MATERIAL.
B. CYTOKINESIS - SECOND STEP. THE
CYTOPLASM OF THE CELL DIVIDES INTOTWO NEW CELLS CALLED DAUGHTER
CELLS.
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MITOSIS
The FOUR Phases of Mitosis are called
PROPHASE, METAPHASE, ANAPHASE,
AND TELOPHASE. (Figure 8-6) THE ACTUALLY PROCESS OF MITOSIS IS
CONTINUOUS.
MITOSIS IS THE PROCESS BY WHICH A
NUCLEUS GIVES RISE TO TWO
IDENTICAL NUCLEI.
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FOUR PHASES OF MITOSIS
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PHASE 1- PROPHASE
1. Chromatin condenses into Chromosomes of TWO Sister Chromatids joined
together by the CENTROMERE, and visible when viewed through a
microscope.
2. THE NUCLEOLUS AND NUCLEAR MEMBRANE DISAPPEAR. 3. TWO Structures called CENTROSOMESappear next to the Disappearing
Nucleus. In Animal Cells, each Centrosome contains a pair of small,
cylindrical bodies called CENTRIOLES. Plant Cells lack Centrioles.
4. In BOTH Animal and Plant Cells, the Centrosomes move toward opposite
poles of the cell. As they Separate, SPINDLE FIBERSmade of microtubulesradiate from the Centrosomes in preparation for Mitosis. The array of Spindle
fibers is called the MITOTIC SPINDLE, whichserves to Equally divides the
Sister Chromatids between the Two Offspring Cells.
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PHASE 2 - METAPHASE
1. The Chromosomes are moved to the
CENTER of the CELL (Equatorial Plane)
by the Kinetochore Fibers attached to theCentromeres.
2. The Two Sister Chromatids of each
Chromosome are attached to KinetochoreFibers radiating from OPPOSITE ENDS OF
THE CELL.
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PHASE 3 - ANAPHASE
The Centromeres of Each Chromosome are
pulled by the Kinetochore Fibers toward the
ends of the cell (OPPOSITE POLES).
2. THE SISTER CHROMATIDS ARE
THUS SEPARATED FROM EACH
OTHER. They are now Considered to beIndividual Chromosomes
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PHASE 4 - TELOPHASE
1. After the Chromosomes reach opposite ends of the Cell, the Spindle Fibers
Disassemble.
2. The Chromosomes return to less tightly coiled Chromatin State.
3. New Nuclear Envelope begins to form around the Chromosomes at each endof the cell.
4. CYTOKINESIS BEGINS.
5. THE PROCESS OF MITOSIS IS NOW COMPLETE. THE CELL
MEMBRANE BEGINS TO PINCH THE CELL IN TWO AS CYTOKINESIS
BEGINS.
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CYTOKINESIS
1. Following the last phase of Mitosis, Cytokinesis COMPLETES the
process of Cell Division.
2. During Cytokinesis, the Cytoplasm of a cell and its ORGANELLES
SEPARATE INTO TWO NEW DAUGHTER CELLS.
3. Cytokinesis proceeds differently in animal and plant cells.
4. CYTOKINESIS OF ANIMAL CELLS:The Cytoplasm Divides when a
GROOVE called the CLEAVAGE FURROWforms through the Middle of
the Parent Cell. The Cleavage Furrow Deepens until the parent cell pinches
into TWO New Identical Cells. The New Cells are Now in INTERPHASE. 5. CYTOKINESIS OF PLANT CELLS: In a Plant Cell, the material for
NEW CELL WALL CALLED THE CELL PLATEAND MEMBRANES
GATHER AND FUSE ALONG THE EQUATOR, OR MIDDLE OF THE
CELL, BETWEEN TWO NUCLEI. Forming TWO New Identical Cells.
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MEIOSIS
Objectives:
List and describe the phases of meiosis.
Compare the end products of mitosis with
those of meiosis.
Explain crossing-over and how it
contributes to the production of unique
individuals.
Summarize the major characteristics of
spermatogenesis and oogenesis.
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MEIOSIS facts 1. Most organisms are capable of COMBINING CHROMOSOMES FROM
TWO PARENTS TO PRODUCE OFFSPRING.
2. WHEN CHROMOSOMES OF TWO PARENTS COMBINE TO
PRODUCE OFFSPRING, THE PROCESS IS KNOWN As SEXUAL
REPRODUCTION.
3. THE CHROMOSOMES THAT COMBINE DURING SEXUAL
REPRODUCTION ARE CONTAINED IN SPECIAL REPRODUCTIVE
CELLS CALLED GAMETES.
4. IN MOST ORGANISMS, GAMETES CAN BE EITHER EGG OR
SPERM.
5. EGGS are larger than sperm and contain a lot of Cytoplasm. An egg is
nonmotile.
6. SPERM Cellscontain very little Cytoplasm, have Flagella, that helps them
swim to the nonmotile egg.
7. The Chromosomes of Two Gametes are added together when they join. The
number of Chromosomes in the offspring DOES NOT DOUBLE WITH
EACH GENERATION, BUT REMAINS THE SAME BECAUSE OF
MEIOSIS.
M i i f t
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Meiosis facts 8. MEIOSISIS THE WAY MANY ORGANISMS PRODUCE GAMETES THROUGH
A TYPE OF CELL REPRODUCTION.
9. MEIOSIS IS A TYPE OF NUCLEAR DIVISIONIN WHICH THE
CHROMOSOME NUMBER IS HALVED. LIKE MITOSIS, MEIOSIS ISFOLLOWED BY CYTOKINESIS.
10. IN HUMANS SPECIALIZED REPRODUCTIVE CELLS WITH 46
CHROMOSOMES (2n) (DIPLOID CELL) UNDERGO MEIOSIS AND
CYTOKINESIS TO GIVE RISE TO EGG OR SPERM THAT HAVE ONLY 23
CHROMOSOMES (1N) (HAPLOID CELL) EACH.
11. MEIOSIS ONLY OCCURS IN EUKARYOTIC CELLS IN PHASES SIMILAR TOTHE PHASES OF MITOSIS.
12. MEIOSIS IS DIFFERENT FROM MITOSIS IN SOME VERY IMPORTANT
WAYS.
A. The process of meiosis results in the production of Daughter Cells that have HALF
THE NUMBER OF CHROMOSOMES OF THE PARENT CELL (HAPLOID CELL). B. Daughter Cell produced by meiosis ARE NOT ALL ALIKE. THE DAUGHTER
CELLS MAY HAVE DIFFERENT CHROMOSOMES FROM EACH OTHER.
C. The NUMBER OF CELLS PRODUCED BY MEIOSIS IS DIFFERENT.
(1) Mitosis - One Parent Cell PRODUCES TWO DIPLOID DAUGHTER CELLS.
(2) Meiosis - One Parent Cell PRODUCES FOUR HAPLOID DAUGHTER CELLS.
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STAGES OF MEIOSIS
THE PROCESS OF MEIOSIS SEPARATES THE PAIRS OF
CHROMOSOMES IN A DIPLOID CELL TO FORM HAPLOID CELLS.
2. ONE PARENT CELL DIVIDES TWICETO PRODUCE FOUR
HAPLOID DAUGHTER CELLS.
3. DURING MEIOSIS, THE NUMBER OF CHROMOSOMES IN EACH
CELL IS REDUCED FROM DIPLOID TO HAPLOID BY SEPARATING
HOMOLOGOUS PAIRS OF CHROMOSOMES.
4. MEIOSIS PROCEEDS IN TWO MAIN STAGES:
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A. MEIOSIS I HOMOLOGOUS PAIRS ARE
SEPARATED.
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B. MEIOSIS II THE SISTER CHROMATIDS
OF EACH CHROMOSOME ARE
SEPARATED.
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MEIOSIS I
1. AT THE START OF MEIOSIS I EACH
CHROMOSOME CONSIST OF TWO STRANDS OF
SISTER CHROMATIDS CONNECTED AT THE
CENTROMERE.
2. HOMOLOGOUS PAIRS OF CHROMOSOMES
COME TOGETHER BEFORE MEIOSIS BEGINS, AN
EVENT THAT DOES NOT OCCUR IN MITOSIS. THIS
EVENT IS CALLED SYNAPSIS.
3. Each Pair of Homologous Chromosomes is called a
TETRAD.
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PROPHASE I. 1. Chromosomes become thick and
visible, the chromosomes of eachhomologous pair are tangled together.
2. Portions of Chromatids may Break
Off and attach to Adjacent Chromatids
on the homologous Chromosome - a
process calledCROSSING-OVER.
(Figure 8-10)
3. Crossing-Over results in Genetic
Recombination by producing a New
Mixture of Genetic Material.
4. Each pair consists of FOUR
CHROMATIDS, BECAUSE EACHCHROMOSOME IN THE PAIR HAD
REPLICATED BEFORE MEIOSIS
BEGAN.
5. The Nucleoli and the Nuclear
Envelope disappear and the spindle
fibers form.