Cell Life, Division, and Reproduction

Specialized Cells

Cells are specialized – have particular function/role Ex: nerve, blood, muscle, sperm, etc

Specialized Cells

Nerve cell – Transmits electrical signals throughout body

Specialized Cells

Blood Cell - Carries Oxygen throughout our bodies to our organs

Specialized Cells

Muscle Cell – contracts to assist the movement of organisms

Specialized Cells

Sperm Cells – sexual reproductive cell for animals

Specialized Cells

Xylem – transports water in vascular plants (plants on land)

Specialized Cells

Phloem – carries sugars and other organic tissues for plants

Cell Life

Organisms begin as masses of undifferentiated cellsDNA expression determines what each cell be

Cell LifeHave same chromosomes and DNADifferentiation – only PARTS of DNA activated determines function/structure of cellAll cells have potential to be any cellDifferentiation occurs, it is irreversible

Cell Life

Different genetic instructions used in different types of cells Cells environment and history Chemical signals released by other cells

Cell Life

Stem Cells – unspecialized cells that reproduce and have ability to specialize into many types of cells Embryonic – found in embryos Adult – found in organisms

http://www.youtube.com/watch?v=8JTw2RpDo9o

http://www.youtube.com/watch?v=tPulEAryPO0&feature=related

http://www.youtube.com/watch?v=slh88WmR8QA&feature=related

Cell Cycle Interphase (cell growth) Mitosis (nuclear division) Cytokinesis (cell division)

InterphaseMost life of cell in interphase

Prepares for division by duplicating chromosomes

Centrioles replicate

InterphaseG1- Cell Grows

S (synthesis)- Replication of DNA

G2- cell prepares to divide

http://www.cellsalive.com/cell_cycle.htm

MitosisCell (somatic) copies it’s DNA and divides to create two new daughter cells - identical to parent

Create new cells Replace damaged or old cells Cell growth

When cell approaches max sizeStages: (phase) pro-, meta-, ana-, telo-

Organization of DNABefore replication, DNA is organized from Chromatin to Chromosomes.Chromatin – long strands of DNA around histones

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Organization of DNA1. Chromatid - one

of the two identical parts of the chromosome, or “sisters”

2. Centromere - Point of attachment.

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Prophase -Chromosomes get small, centrioles move to the poles of the cell, and spindle fibers develop

Pair of Centrioles

Spindle Fibers

Chromosomes consisting of 2 Sister Chromatids

Prophase - Nuclear Envelope disintegrates, spindle fibers move chromosomes toward the center of cell.

Spindle Fibers

Chromosomes

Metaphase - Chromosomes line up across center of the cell

Spindle Fibers

Chromosomes

Center of Cell

Anaphase - Chromatids move apart and travel to opposite ends of cellular spindle

Chromatids

Chromosome

Chromatid

Telophase - envelope surrounds each set of Chromatids to form new Nucleus and the Cytoplasm starts to divide

Cleavage Furrow

Cytokinesis - Cytoplasm divides and two cells with identical genetic material are formed

Daughter Cells

CytokinesisIn plants Cell plate laid down

across middle Membrane forms

around each cell Cell walls form on

each side

In animals Plasma membrane

pinches in

Mitosis

Cell Size LimitationsDiffusion-

• diffusion is slow

DNA – • has to be enough to support protein needs

Surface area-to-volume• ratio too large, cell cannot function properly

Control of Cell Cycle Controlled by cyclin proteins and enzymes

Cells lose control – over/under/failure of production or certain enzymes

Loss of control = malignant growth “Cancer”

Cancer Masses, or tumors, deprive cells from nutrientsSecond leading C.O.D. in U.S.Causes- Environmental factors Some more prone than others

Cancer PreventionHealthy Lifestyle Low fat high fiber Fruits, vegetables, grains Vitamins and minerals Exercise and tobacco free!!

Meiosis

Why We Are Who We Are

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Why Meiosis?Mitosis- cells are clones (asexual) Parent cell – n# of chromosomes;

Daughter cells – n# of chromosomes Offspring would have 2x chromosomes

Meiosis – division of sex cells Offspring has same number of

chromosomes after fertilization Diploid – Haploid (sex cells)

DiploidDi= twoContains both sets of homologous chromosomesNumber of chrms in diploid cell represented by 2N

Haploid

Means “one set”Only one set of chromosomesGametes (sex cells) Sperm and egg

Represented by NZygote- fertilized egg; sexual reproduction Turns into multicellular by mitosis

MeiosisNumber of chromosomes is cut in half through the separation of homologous chromosomes in a diploid cell

Chromosome Number

Homologous chromosomes Chromosome that has a corresponding

chromosome, one from each parent

Sister chromatid

Tetrad

Meiosis

Meiosis I A diploid cell enters here PMAT 1

Meiosis II The diploid cell that entered

meiosis has become 4 haploid cells PMAT 2

PhasesProphase 1 Each chromosome pairs with its

homologous chromosome Exchange portions of chromatids in the

process …. CROSSING OVER

Crossing Over

Metaphase 1Spindle fibers attach to chromosomes and line them up side by side

Anaphase 1• The spindles pull homologous

chromosomes apart to opposite poles/ends

Telophase 1• Nuclear membranes form and cell

separates into two new cells

Meiosis IISimply mitotic division of productsOnly difference is chromosomes do not replicate before they divide

Genetic VariationGenetic recombination Reassortment of chromosomes by

crossing over or segregation of homol. chromosomes

Polyploidy More than two sets; often in plants

NondisjunctionTrisomy – has an extra chromosome Gamete with extra fuses with

gamete with one

Monosomy- missing chromosome (fatal)

Homologous chrms. do not separate, can cause tri and tetrasomy

NondisjunctionTypes XO – Turner’s syndrome XXX – Trisomy X (metafemales) XXY – Klinefelter’s syndrome XYY- Jacob’s Syndrome OY – males (lethal)

Gene Linkage and Maps

Linked – genes close on same chromosome inherited togetherCan separate via crossing over Gene combinations to make chromosome map w/ relative locations