chromosomes morphology and mitosis

Chapter IV Reproduction of prokaryotic cell

Reproduction of Eukaryotic cell/ Cell division

4.1Chromosome morphology and function4.2 The cell cycle and mitosisOutline

Chromosome, Bacterial

4All eukaryotic cells store genetic information in chromosomesMost eukaryotes have between 10 and 50 chromosomes in their body cellsHuman body cells have 46 chromosomes or 23 identical pairs

Eukaryotic Chromosome

Chromosomes vs. ChromatinChromosomesTightly packaged DNAFound only during cell divisionDNA is not being used for macromolecule synthesisChromatinUnwound DNAFound throughout InterphaseDNA is being used for macromolecule synthesis

Chromosomes, Eukaryote

Though chromosomes are all about DNA, in fact much this structure consists of proteinForm via replication, not by formed chromatids coming together

8Duplicated chromosomes are called chromatids & are held together by the centromere

Called Sister ChromatidsChromosomes in dividing cells

Chromosome Duplication & Distribution During Cell DivisionA eukaryotic cell has multiple chromosome, one of which is represented here. Before duplication, each chromosome has a single DNA molecule.

Once replicated, a chromosome consists of two sister chromatids connected along their entire lengths by sister chromatidcohesion. Each chromatid contains a copy of the DNA molecule

Mechanical processes separate the sister chromatids into two chromosomes and distibute them to two daughter cells.

ChromosomesDNA molecules

How Long is a Chromatid a Chromatid?A chromatid is a chromatid as long as it is held in association with a sister chromatid at the centromere

Homologous ChromosomeCentromereSister Chromatid Sister ChromatidWhen two sister chromatids separate (after metaphase) they go from being a single chromosome to being two different chromosomes

Chromosomes, Eukaryote

Here chromosome and DNA are not 100% synonymous

Chromosomes, EukaryoteGenome =DNAChromosome =DNA + protein(visible light microscope)Chromatin =DNA + protein(but less than for chromosome)DNA

13DNA is tightly coiled around proteins called histones

Compacting DNA into chromosomes

DNA strand tightly coiled around group of small protein

Forming a series of bead like structures

The string of nucleosomes compacted by factor of 6, then coiled into an even denser

DNA strand wraps around group of small protein, HISTONESForming a series of bead like structures, NUCLEOSOMESConnected by DNA strandThe string of nucleosomes compacted by factor of 6, then coiled into an even denser, SOLENOIDSolenoid structure then coils to form hollow tubeThis complex compression and structuring DNA then serves several functions.

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18A picture of the chromosomes from a human cell arranged in pairs by sizeFirst 22 pairs are called autosomesLast pair are the sex chromosomesXX female or XY male

Karyotype

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Boy or Girl?Y - ChromosomeX - ChromosomeThe Y Chromosome Decides

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20The Cell Cycle

Some VocabularyCentromereCentrosomeCentrioleKinetochoreKinetochore microtubulesMitotic spindleNonkinetochore microtublesSpindle apparatusSpindle fibers


Recall that the centrosome is the center of the microtubule array of a cell


Keep in mind that the term centriole is not an exact synonym of centrosome and thatcentrosome is not a synonym of the term centromereRecall that these consist of microtubules and that a pair makes up a centrosome


Responsible for moving chromosomes relative to mitotic spindle


These are the portion of the mitotic spindle that is connected to chromosomes during mitosis


These are the microtubles that are responsible for separating chromosomes as well as pushing the centrosomes toward opposite ends of cells


Microtubules of mitotic spindle that are not connected to the chromosomes but instead responsible for pushing centrosome apart


The mitotic spindle as visible through a light microscope


Bundles of microtubles making up the spindle apparatus; it is the bundling that makes them visible through a light microscope

Eukaryote Cell Cycle


Primary growth phase1st growth stage after cell divisionCells mature by making more cytoplasm & organellesCell carries on its normal metabolic activities


SynthesisSynthesis stageDNA is copied or replicated

Two identical copies of DNAOriginal DNAInterphase- S stage


Secondary growth phase2nd Growth StageOccurs after DNA has been copiedAll cell structures needed for division are made (e.g. centrioles)Both organelles & proteins are synthesized

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What the cell looks likeAnimal Cell

Whats occurring

Summary - Interphase


M phaseDivision of the nucleusAlso called karyokinesisOnly occurs in eukaryotesDoesnt occur in some cells such as brain cells

Mitosis is conventionally divided into four phases:

ProphaseMetaphaseAnaphaseTelophase

Cytokinesis is well underway by latetelophase

MITOSIS

37For the Cell Biology Video Myosin and Cytokinesis, go to Animation and Video Files.

38Used for growth and repairProduce two new cells identical to the original cellCells are diploid (2n)

Chromosomes during Metaphase of mitosis

Prophase

Metaphase

Anaphase

Telophase

Cytokinesis

Eukaryotic Cell division

Stages of Mitosis

Mitosis (First half)

Nucleus defined, Nucleoli present, Replicated Centrosomes, Asters present, DNA duplicated, DNA still chromatin

1. G2 of Interphase1.


Chromatin in nucleus condenses to form visible chromosomesMitotic spindle forms from fibers in cytoskeleton or centrioles (animal)

2. Early Prophase2.


Nuclear membrane & nucleolus are broken downChromosomes continue condensing & are clearly visibleSpindle fibers called kinetochores attach to the centromere of each chromosomeSpindle finishes forming between the poles of the cell

3. Prophase3.

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Kinetochore Fiber

Chromosome

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What the cell looks like

Whats happeningReview - Prophase

45The mitotic spindle form from the microtubules in plants and centrioles in animal cellsPolar fibers extend from one pole of the cell to the opposite poleKinetochore fibers extend from the pole to the centromere of the chromosome to which they attach

Mitotic Spindle

Mitotic Spindle

Aster(s)

Asters are short fibers radiating from centrioles

Mitosis (Second half)

Chromosomes, attached to the kinetochore fibers, move to the center of the cellChromosomes are now lined up at the equator

4. Metaphase4.

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Whats occurring

Review - Metaphase


Occurs rapidlySister chromatids are pulled apart to opposite poles of the cell by kinetochore fibers

5. Anaphase5.

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Whats occurring

Review Anaphase


Sister chromatids at opposite polesSpindle disassemblesNuclear envelope forms around each set of sister chromatidsNucleolus reappearsChromosomes reappear as chromatin

6. Telophase6.

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Comparison

55Means division of the cytoplasmDivision of cell into two, identical halves called daughter cellsCytokinesis

Cytokinesis, Animals

Cytokinesis can occur simultaneous to telophasecleavage furrow forms to split cell

Cytokinesis, Plants

cell plate forms at the equator to divide cell

Cytokinesis

Cleavage Furrow

59Have the same number of chromosomes as each other and as the parent cell from which they were formedIdentical to each other, but smaller than parent cellMust grow in size to become mature cells (G1 of Interphase)

Daughter cell of mitosis

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Chromosome number the same, but cells smaller than parent cellWhat is the 2n or diploid number?

2

61If mitosis is not controlled, unlimited cell division occurs causing cancerous tumorsOncogenes are special proteins that increase the chance that a normal cell develops into a tumor cell

Cancer cellsUncontolled mitosis

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Draw & Learn these Stages

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Draw & Learn these Stages

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InterphaseProphaseMetaphaseAnaphaseTelophaseName the Mitotic Stages:Name this?

Name this?

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Mitosis AnimationName each stage as you see it occur?

66Identify the Stages

Early, Middle, & Late Prophase Late ProphaseMetaphaseAnaphaseLate AnaphaseTelophaseTelophase & Cytokinesis?

??????

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Mitosis Quiz

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Mitosis Quiz

chromosomes morphology and mitosis

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