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

Phases of mitosis

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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

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