Cell division,Mitosis cell cycle 2013.ppt

Cell Division

04/17/23Cell division, Mitosis, cell cycle

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Learning outcomes

• Describe Chromosome structure• Explain Mitosis: Interphase, Prophase,

Metaphase, Anaphase, Telophase• Describe the Significance of mitosis


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Why Is Cell Division Important ?

• Cell division is important to multi-celled and single celled organisms, like bacteria and algae.

• All cells go through cell division in what is called the cell cycle.

• Cell cycle starts with cell formation followed by growth and finally ends in the death of the cell.


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Cell Division• All cells are derived from pre-

existing cells• New cells are produced for growth

and to repair tissues• Differs in prokaryotes (bacteria) and

eukaryotes (protists, fungi, plants, & animals)


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DNA Replication• DNA must be

copied or replicated before cell division

• Each new cell will then have an identical copy of the DNA


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Original DNA strand

Two new, identical DNA

strands

Identical Daughter Cells


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Parent Cell

Two identical daughter

cells

Chromosomes


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Prokaryotic Chromosome

The DNA of prokaryotes (bacteria) is one, circular chromosome attached to the inside of the cell membrane

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Eukaryotic Chromosomes

• All eukaryotic cells store genetic information in chromosomes

• Most eukaryotes have between 10 and 50 chromosomes in their body cells

• Human body cells have 46 chromosomes or 23 identical pairs

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Compacting DNA into Chromosomes

DNA is tightly coiled around proteins called histones


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Chromosomes in Dividing Cells

Duplicated chromosomes are called chromatids & are held together by the centromere

04/17/23 11Called Sister Chromatids

Karyotype

• A picture of the chromosomes from a human cell arranged in pairs by size

• First 22 pairs are called autosomes

• Last pair are the sex chromosomes

• XX female or XY male

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Karyotype


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Cell Reproduction

• Asexual reproduction involves a single cell dividing to make 2 new, identical daughter cells

• Mitosis & binary fission are examples of asexual reproduction


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False-Colour EMof Dividing Bacterium

CytoplasmCytoplasm

Division planeDivision plane

Cell wall

Nuclear material


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Prokaryotic Cell Undergoing Binary Fission


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Yeasts:Asexual Reproduction by Mitosis

• Budding• Nucleus divides by

mitosis• Bud forms on cell• Nucleus moves into bud• Bud separates


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Protozoa:Asexual Reproduction by Mitosis


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New individualsNew individuals

Functions of Mitosis


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Mitotic Mitotic

cell divisioncell division

Mitotic cell Mitotic cell division & division &

differentiationdifferentiation

OrgansOrgans

TissuesTissues

The Cell Cycle


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Five Phases of the Cell CycleCycle• G1 - primary growth phase• S – synthesis; DNA replicated• G2 - secondary growth phase

–collectively these 3 stages are called interphase

• M - mitosis• C - cytokinesis


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Cell Cycle


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Interphase• Cells spent most time in Interphase, in which the

cell grows and develops.

• During the later part of interphase the cell duplicates all of its chromosomes, and prepares to undergo mitosis.

• When chromosomes duplicate they form 2 chromatids.

• The cells copy chromosomes before mitosis so that the two new cells that are going to be made have an equal amount of chromosomes


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Interphase - G1 Stage

• 1st growth stage after cell division

• Cells mature by making more cytoplasm & organelles

• Cell carries on its normal metabolic activities


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Interphase – S Stage• Synthesis stage

• DNA is copied or replicated


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Two identical copies of

DNA

Original DNA

Interphase – G2 Stage• 2nd Growth Stage

• Occurs after DNA has been copied

• All cell structures needed for division are made (e.g. centrioles)

• Both organelles & proteins are made


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What’s Happening in Interphase?

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What the cell looks like

Animal Cell

What’s occurring

The Cell Cycle

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Daughter Cells

DNA Copied

Cells Matur

e

Cells prepare for Division

Cell Divides into Identical cells

Mitosis


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Four Mitotic Stages

• Prophase

• Metaphase

• Anaphase

• Telophase

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Early Prophase• Chromatin in nucleus condenses to form

visible chromosomes• Mitotic spindle forms from fibres in

cytoskeleton or centrioles (animal)


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Chromosomes

Nucleolus Cytoplasm

Nuclear Membrane

Late Prophase

• Nuclear membrane & nucleolus are broken down

• Chromosomes continue condensing & are clearly visible

• Spindle fibers (kinetochores) attach to the centromere of each chromosome

• Spindle finishes forming between the poles of the cell


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Late Prophase

04/17/23 34Nucleus & Nucleolus have disintegrated

Chromosomes

Spindle Fibre attached to Chromosome

Cell division, Mitosis, cell cycle 35

Spindle (Kinetochore) Fibre

Chromosome

Spindle Fibres

• The mitotic spindle form from the microtubules in plants and centrioles in animal cells

• Polar fibers extend from one pole of the cell to the opposite pole

• Spindle (Kinetochore) fibres extend from the pole to the centromere of the chromosome to which they attach

• Asters are short fibers radiating from centrioles


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The Spindle


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Metaphase• Chromosomes, attached to the kinetochore fibers,

move to the center of the cell• Chromosomes are now lined up at the equator

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Pole of the Cell

Equator of Cell

Metaphase


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Aster

Chromosomes at Equator

Anaphase

• Occurs rapidly

• Sister chromatids are pulled apart to opposite poles of the cell by Spindle(kinetochore) fibers


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Anaphase


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Sister Chromatids

being separated

Telophase

• Sister chromatids at opposite poles• Spindle disassembles• Nuclear envelope forms around

each set of sister chromatids• Nucleolus reappears• Cytokinesis occurs• Chromosomes reappear as

chromatin


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Cytokinesis

• Means division of the cytoplasm• Division of cell into two identical halves

called daughter cells• In plant cells, cell plate forms at the

equator to divide cell• In animal cells, cleavage furrow forms to

split cell


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Cytokinesis


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Cleavage furrow in animal cell

Cell plate in plant cell

Extra


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Name the Mitotic Stages:

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Interphase

Prophase

MetaphaseAnaphase

Telophase

Name this?

Name this?

04/17/23

Mitosis Animation


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Name each stage as you see it occur?

Name the Stages of Mitosis:

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Interphase

Early prophase

Mid-ProphaseLate Prophase

Metaphase

Late Anaphase

Early Anaphase

Early Telophase,

Begin cytokinesis

Late telophase, Advanced cytokinesis

Cell division, Mitosis, cell cycle

Identify the Stages

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Early, Middle, & Late Prophase

Late Prophase Metaphase Anaphase

Late Anaphase Telophase Telophase & Cytokinesis

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? ? ?

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Mitosis in Onion Root Tips


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Do you see any stages of mitosis?

Cell division,Mitosis cell cycle 2013.ppt

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