Mitosis: Cell Division
New cells are produced:for growth to replace damaged or old cells
For asexual reproduction in some organisms
Interphase – cell copies DNA and prepares for divisionMitosis – chromosomes separate into two new cells
Cell Division - process by which a cell splits into two identical daughter cells
*Occurs in two main phases:
•DNA containing cell’s genetic code
•Each chromosome has a matching pair (homologous)
•During interphase, each chromosome copies itself
What are chromosomes?
•Mitosis = nuclear division
•Mitosis is followed by cytokinesis (cell division)
•The steps of mitosis ensure that each new cell has the exact same number of chromosomes as the original
•Interphase = growth phase, differentiation occurs
Life Cycle of the Cell
DNA ReplicationDNA must be copied before cell division
Each new cell will then have an identical copy of the DNA
Happens during the S (synthesis) phase of cell cycle
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The Cell Cycle
Interphase (longest phase)
G1 - first growth (gap) phaseSynthesis - DNA makes a copyG2 - second growth (gap) phase, preparing for mitosis
Mitosis - nucleus divides, ensuring each new cell has the exact number of chromosomes as parent
Uncontrolled Cell DivisionIf the cell cycle is
not controlled, cell division does not stop and forms tumors.
Cancer is uncontrolled cell division
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Cancer cells
Uncontrolled Cell Division
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Cancer cells do not carry out necessary functions.
DefinitionsHomologous chromosomes
a pair of chromosomes that are similar and carry genes for the same traits
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One chromosome comes from the mother, the other comes from the father.
Diploid vs. Haploiddiploid (2n) cells have a full set of chromosomes - pairs of homologous chromosomes.
haploid (n) cells are Sex cells or gametes and have ½ the diploid number of chromosomes - one chromosome from each homologous pair.
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MITOSIS
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Mitosis is Cell division that begins with 1 diploid cell and ends with 2 diploid cells
Asexual reproduction
•Interphase • Prophase • Metaphase • Anaphase • Telophase
•IPMAT
1. chromosomes visible (chromatids)2. centrioles migrate to the poles3. nuclear membrane disappears4. spindle forms
1. chromosomes line up on the equator, spindle attaches
1. chromatids separate and move to opposite poles
1. chromosomes unwind2. nuclear membrane reforms3. spindle disappears
- division of the cytoplasm to form 2 new daughter cells- organelles are divided- daughter cells are genetically identical
Cells return to interphase
1.Name the phases starting at the top.
1.Name the phase2.Identify X3.Identify Y
5. Name the phase
6. Name the phase
Meiosis
Meiosis is the formation of gametes or sex cells (egg and sperm)
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Meiosis I
MeiosisII
Diploid
Haploid
Meiosis Forms Haploid Gametes
Meiosis is cell division that reduces the number of chromosomes.
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from mom from dad child
meiosis reducesgenetic content
toomuch!
The right number!
Meiosis
It begins with one diploid cell and ends with 4 haploid cells.Meiosis is part of sexual reproduction.Fertilization is when two haploid gametes join to form a diploid zygote.
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Crossing-Over1. Homologous
chromosomes cross over each other in meiosis
2. Pieces of chromosomes or genes are exchanged
3. Produces Genetic variation in the offspring
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KaryotypeA picture of
chromosomes arranged in pairs
First 22 pairs are called autosomes
Last pair are the sex chromosomes
XX female or XY male
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Boy or Girl?
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Y - Chromosome
X - Chromosome
The Y Chromosome Decides
Comparing Mitosis and
Meiosis35
Comparison of Mitosis and Meiosis
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MITOSIS MEIOSISREPRODUCTION TYPEPURPOSE
# CELLS START# CELLS ENDCHROMOSOMES START (haploid/diploid)CHROMOSOMES END (haploid/diploid)
asexual
Grow, repair, reproduction (in
some organisms)
1
2
diploid
diploid
sexual
Produce gametes
1
4
diploid
haploid
Asexual & Sexual Reproduction
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Asexual SexualCELL DIVISION
Process
Advantages
Genetic Variation
mitosis
Produces identical diploid cells
• Identical cells are produced
• Only one parent• good in unchanging
conditions
No
meiosis
Produces haploid gametes that join to form a diploid zygote
• Not identical to parent• Un-wanted traits might not be
passed on• Needed traits for adaptation are
passed on• Good in changing conditions
Yes
Pop Quiz / Exit Ticket
D
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