Cell Cell Reproduction Reproduction

UnitUnit

Chromosome StructureChromosome Structure

- chromosome = a long - chromosome = a long continuous thread of DNA that continuous thread of DNA that consists of numerous genes consists of numerous genes with regulatory information with regulatory information coiled around proteins in coiled around proteins in compact structurescompact structures

Chromosome StructureChromosome Structure

- DNA wraps around proteins - DNA wraps around proteins (called histones) to become (called histones) to become compactcompact

Chromosome FormationChromosome Formation

Chromosome StructureChromosome Structure (cont)

Cell CycleCell Cycle

= the regular pattern of = the regular pattern of growth, DNA duplication, growth, DNA duplication, and cell division that occurs and cell division that occurs in cellsin cells

Cell CycleCell Cycle

- results in two cells - results in two cells (daughter cells) identical to (daughter cells) identical to one anotherone another

- made up of 5 Phases- made up of 5 Phases

Cell CycleCell Cycle (cont) (cont)

1) G1) G11 Phase = cell growth Phase = cell growth

2) S Phase = DNA is copied2) S Phase = DNA is copied

3) G3) G22 Phase = cell prepares Phase = cell prepares

for cell divisionfor cell division

Together Phases 1-3 are Together Phases 1-3 are called Interphasecalled Interphase

Cell CycleCell Cycle (cont) (cont)

4) M Phase (Mitosis) 4) M Phase (Mitosis) - division of the nucleus- division of the nucleus

5) C Phase (Cytokinesis) 5) C Phase (Cytokinesis) - division of the cytoplasm- division of the cytoplasm

Cell CycleCell Cycle (cont) (cont)

Sequence of the Cell CycleSequence of the Cell Cycle

GG11 S G S G22 M C M C

Cell CycleCell Cycle (cont) (cont)

Cell CycleCell Cycle (cont) (cont)

MitosisMitosis

= division of the nucleus = division of the nucleus and its contentsand its contents

- discovered by Walther - discovered by Walther Flemming in 1882Flemming in 1882

Phases Phases of of

MitosisMitosis

1) Prophase1) Prophase- DNA coils to become - DNA coils to become

chromosomeschromosomes

- nuclear membrane disappears- nuclear membrane disappears

- microtubules called spindle - microtubules called spindle fibers grow from centrioles to fibers grow from centrioles to center of cellcenter of cell

1) Prophase1) Prophase (cont) (cont)Spindle Fibers: 2 TypesSpindle Fibers: 2 Types

1) Kinetochore Fibers – 1) Kinetochore Fibers – attach to chromosomes (at attach to chromosomes (at centromere)centromere)

2) Polar Fibers – spread 2) Polar Fibers – spread throughout cellthroughout cell

ProphaseProphase

Nucleus with Chromosomes

Centrioles

Spindle Fibers

Late ProphaseLate Prophase

Polar Fibers

Kinetochore Fibers

2) Metaphase2) Metaphase

- chromosomes line up - chromosomes line up in centerin center

MetaphaseMetaphase

3) Anaphase3) Anaphase

- chromosomes pull - chromosomes pull apart and move to apart and move to opposite sides of cellopposite sides of cell

AnaphaseAnaphase

4) Telophase4) Telophase

- chromosomes uncoil- chromosomes uncoil- nuclear membrane reforms- nuclear membrane reforms

TelophaseTelophase

New Nuclear Membrane Forms

Chromosomes Uncoil

Phases of MitosisPhases of Mitosis

How do you remember How do you remember the order of the phases the order of the phases of Mitosis?of Mitosis?

Just remember this Just remember this phrase……….phrase……….

PMATPMAT

P = ProphaeP = Prophae

M = MetaphaseM = Metaphase

A = AnaphaseA = Anaphase

T = TelophaseT = Telophase

PEEMATT

CytokinesisCytokinesis

- cell membrane forms a - cell membrane forms a cleavage furrow and cleavage furrow and cytoplasm dividescytoplasm divides

- in plants, a cell plate forms - in plants, a cell plate forms between each cellbetween each cell

CytokinesisCytokinesis

Cleavage Furrow

Cell PlateCell Plate

Regulation of Cell DivisionRegulation of Cell Division

- controlled by external and - controlled by external and internal factorsinternal factors

- External Factors- External Factors

1) cell to cell contact1) cell to cell contact

2) growth factors 2) growth factors

Cell to Cell ContactCell to Cell Contact

Regulation of Cell DivisionRegulation of Cell Division (cont) (cont)

Growth Factors – ExamplesGrowth Factors – Examples- Platelets- Platelets

Regulation of Cell DivisionRegulation of Cell Division (cont) (cont)

Growth Factors – ExamplesGrowth Factors – Examples- Erythropoietin- Erythropoietin(stimulates red(stimulates redblood cell blood cell production)production)

Regulation of Cell DivisionRegulation of Cell Division (cont) (cont)

- Internal Factors- Internal Factors- enzymes and proteins - enzymes and proteins released by the cellreleased by the cell

Regulation of Cell DivisionRegulation of Cell Division (cont) (cont)

- apoptosis = programmed cell - apoptosis = programmed cell deathdeath

Webbed Fingers

Apoptosis – Leaves in FallApoptosis – Leaves in Fall

Incomplete ApoptosisIncomplete Apoptosis

Cancer cells form tumors that may Cancer cells form tumors that may metastasize to other parts of the bodymetastasize to other parts of the body

A healthy cell may A healthy cell may become a cancer become a cancer cell if certain cell if certain genes are genes are damageddamaged

Normal Cell Cancer Cell Bloodstream

Cancer cells form tumors that may Cancer cells form tumors that may metastasize to other parts of the bodymetastasize to other parts of the body

Cancer cells Cancer cells divide more often divide more often than do healthy than do healthy cells and may cells and may form disorganized form disorganized clumps called clumps called tumorstumors

Cancer cells form tumors that may Cancer cells form tumors that may metastasize to other parts of the bodymetastasize to other parts of the body

Sometimes Sometimes cancer cells break cancer cells break away from the away from the tumor. They can tumor. They can be carried in the be carried in the bloodstream to bloodstream to other parts of the other parts of the body where they body where they form new tumors.form new tumors.

This cancerous This cancerous mole is an mole is an example of a example of a skin cancer, skin cancer, which may which may metastasize metastasize quickly.quickly.

According to the American Cancer According to the American Cancer Society, skin cancer is the most Society, skin cancer is the most common of all cancers.common of all cancers.

ABCD Rule (for moles, etc)ABCD Rule (for moles, etc)Mnemonic to help remember what to look forMnemonic to help remember what to look for

A = A = AAsymmetry (irregular shape)symmetry (irregular shape)

B = B = BBorder is irregular shapeorder is irregular shape

C= C= CColor change (changing or many colors)olor change (changing or many colors)

D = D = DDimension (1/4 in or less)imension (1/4 in or less)

**other key signs to look for:**other key signs to look for:

New growth, changes in growth, painful New growth, changes in growth, painful feelingfeeling

Look for the ABCD Rule in this mole?Look for the ABCD Rule in this mole?

Why is sex with Why is sex with someone else someone else better than sex by better than sex by yourself?yourself?

= reproduction of offspring = reproduction of offspring from one parentfrom one parent

- offspring are genetically - offspring are genetically identical to the parent identical to the parent

… …this is a BAD thingthis is a BAD thing

Asexual ReproductionAsexual Reproduction

= reproduction of offspring = reproduction of offspring from two parentsfrom two parents

- offspring are genetically - offspring are genetically different from the parents different from the parents

… …this is a GOOD thingthis is a GOOD thing

Sexual ReproductionSexual Reproduction

Example Example

Nut Nut Disease Disease in in SquirrelsSquirrels

Some eukaryotic cells divide by Some eukaryotic cells divide by mitosismitosis

Some organisms can reproduce Some organisms can reproduce by asexual or sexual reproduction by asexual or sexual reproduction (depends on conditions) (depends on conditions)

MeiosisMeiosis

= cell reproduction that = cell reproduction that forms gametes (= sex forms gametes (= sex cells = egg/sperm)cells = egg/sperm)

MeiosisMeiosis

- # of chromosomes is - # of chromosomes is halvedhalved

- produces haploid cells- produces haploid cells

(23 chromosomes)(23 chromosomes)

Meiosis (cont)Meiosis (cont)

Two Stages:Two Stages:

Meiosis IMeiosis I

Prophase I, Metaphase I, Prophase I, Metaphase I, Anaphase I, Telophase IAnaphase I, Telophase I

Meiosis IIMeiosis II

Prophase II, Metaphase II, Prophase II, Metaphase II, Anaphase II, Telophase IIAnaphase II, Telophase II

Meiosis (cont)Meiosis (cont)

Homologous chromosomes line Homologous chromosomes line up ( = tetrad)up ( = tetrad)

Portions of chromatids are Portions of chromatids are exchanged ( = crossing over)exchanged ( = crossing over)

- results in new mixture of - results in new mixture of genetic material ( = genetic genetic material ( = genetic recombination)recombination)

Meiosis (cont)Meiosis (cont)

Meiosis (cont)Meiosis (cont)

Chromosomes separate Chromosomes separate randomly ( = law of randomly ( = law of independent assortment)independent assortment)

- results in genetic - results in genetic variationvariation

Meiosis (cont)Meiosis (cont)

Meiosis (cont)Meiosis (cont)

= production of sperm = production of sperm cellscells

- makes 4 haploid cells - makes 4 haploid cells called spermatidscalled spermatids

SpermatogenesisSpermatogenesis

SpermatogenesisSpermatogenesis

= production of egg cells= production of egg cells

- makes 1 haploid egg cell - makes 1 haploid egg cell and 3 polar bodiesand 3 polar bodies

- polar bodies degenerate- polar bodies degenerate

OogenesisOogenesis

OogenesisOogenesis

Examples: Examples: Mitosis vs. MeiosisMitosis vs. Meiosis

Examples: Mitosis vs. MeiosisExamples: Mitosis vs. Meiosis

A human has 46 chromosomesA human has 46 chromosomes

- after mitosis, each body cell - after mitosis, each body cell has 46 chromosomeshas 46 chromosomes

- after meiosis, each sex cell - after meiosis, each sex cell (egg and sperm) has 23 (egg and sperm) has 23 chromosomeschromosomes