AP BiologyAdapted from: Kim Foglia

Chapter 13:The Cell Cycle

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How did you get from there

to here?

And now look at you…

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Getting from there to here… Cell division

continuity of life = reproduction of cells reproduction

unicellular organisms

growth repair & renew

Cell cycle life of a cell from

origin to division into 2 new daughter cells

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A bit about DNA DNA is organized in

chromosomes double helix DNA molecule associated proteins =

histone proteins Nucleosome = a segment of

DNA wrapped around 8 histone proteins

DNA-protein complex =chromatin organized into long

thin fiber

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Chromosome Duplicated

chromosome consists of 2 sister chromatids meet at the

centromere contain identical

copies of the chromosome’s DNA

Telomeres = repeated sequence at end of each arm

p= short arm; q= long arm

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Prokaryotic Chromosome Structure

Bacteria have a one single loop of DNA

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Types of Cells & Ploidy Levels There are two types of human cells: somatic

cells and gametes. Somatic Cells = body cells (brain, muscle, heart,

liver, skin, etc) Contain 46 chromosomes in humans Diploid (2n)= cell that contains two sets of homologous

chromosomes 23 PAIRS of homologous chromosomes = 46 TOTAL

chromosomes

Gametes = sex cells (sperm or egg) Contain 23 chromosomes in humans Haploid (n)= cell that contains one set of chromosomes

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FertilizationWhen sperm meets egg a zygote is formed. A zygote is the first cell of the embryo.

Which of the cells above are haploid (n)? Diploid (2n)?

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Homologous Chromosomes

Chromosomes containing the same type of genetic information

one comes from male parent, one comes from female parent

DAD MOM

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Homologous Chromosomes

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The chromosomes diagrammed below are arranged in a karyotype, the 46 chromosomes have been arranged in homologous pairs.

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The first 22 pairs of homologous chromosomes are called autosomes or autosomal chromosomes.

The 23rd pair of chromosomes determines the sex of the individual and are called sex chromosomes.

The sex chromosomes of a female are XX.The sex chromosomes of a male are XY.

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What’s the difference?

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Cell cycle Cell has a “life cycle”

cell is formed from a mitotic division

cell grows & maturesto divide again

cell grows & matures to never divide again

G1, S, G2, M G0

epithelial cells,blood cells,stem cells

brain nerve cells

liver cells

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Cell Division cycle Phases of a dividing

cell’s life interphase

cell grows replicates chromosomes produces new organelles & biomolecules

mitotic phase cell separates & divides chromosomes

mitosis cell divides cytoplasm & organelles

cytokinesis

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Control of Cell Cycle

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Interphase 90% of cell life cycle

cell doing its “everyday job” produce RNA, synthesize proteins

prepares for duplication if triggered

Characteristics nucleus well-defined DNA loosely

packed in long chromatin fibers

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Interphase Divided into 3 phases:

G1 = 1st Gap S = DNA Synthesis G2 = 2nd Gap

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Interphase

G1 – First stage after division Cell recovers from previous division Cell increases in size Doubles organelles Accumulates materials for DNA replication Cells do everyday jobs

G0 – Some cells don’t complete the cycle (nerve and heart muscle) Continue normal cell operations No preparation for cell division Cells will operate in this stage until organism

dies

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Interphase

S Stage – DNA synthesis occurs At the beginning it contains chromosomes containing

one DNA strand At the end each chromosome contains two identical

strands of DNA Copies chromosomes

G2 – Growth & final preparations for division Prepares for division Ends with mitosis Proteins that aid in mitosis are made in this stage

Microtubules Nucleus well-defined DNA loosely packed

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Interphase Nucleus well-defined

chromosome duplication complete

DNA loosely packed in long chromatin fibers

Prepares for mitosis produces proteins &

organelles

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Mitosis copying cell’s DNA & dividing it

between 2 daughter nuclei Mitosis – division of the nucleus

is divided into 5 phases Prophase Prometaphase metaphase anaphase telophase

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Overview

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Prophase Chromatin (DNA) condenses

visible as chromosomes chromatids

fibers extend from the centromeres

Centrioles move to opposite poles of cell

Fibers (microtubules) cross cell to form mitotic spindle actin, myosin

Nucleolus disappears Nuclear membrane breaks down

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Prometaphase Proteins attach to

centromeres creating kinetochores

Microtubules attach at kinetochores connect centromeres to

centrioles

Chromosomes begin moving

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Kinetochore Each chromatid

has own kinetochore proteins microtubules

attach to kinetochore proteins

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Metaphase Spindle fibers align

chromosomes along the middle of cell meta = middle metaphase plate helps to ensure

chromosomes separate properly so each new nucleus

receives only 1 copy of each chromosome

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Anaphase Sister chromatids

separate at kinetochores move to opposite poles pulled at centromeres pulled by motor proteins

“walking”along microtubules increased production of

ATP by mitochondria

Poles move farther apart polar microtubules

lengthen

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Separation of chromatids In anaphase, proteins holding together

sister chromatids are inactivated separate to become individual

chromosomes

2 chromosomes1 chromosome2 chromatids

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Kinetochores use motor proteins that “walk” chromosome along attached microtubule microtubule

shortens by dismantling at kinetochore (chromosome) end

Chromosome movement

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Telophase Chromosomes arrive at

opposite poles daughter nuclei form nucleoli from chromosomes disperse

no longer visible under light microscope

Spindle fibers disperse Cytokinesis begins

cell division

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Cytokinesis Animals

cleavage furrow forms ring of actin

microfilaments forms around equator of cell myosin proteins

tightens to form a cleavage furrow, which splits the cell in two like tightening a draw

string

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Cytokinesis in Animals

(play Cells Alive movie here)

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Mitosis in whitefish blastula

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Mitosis in animal cells

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Cytokinesis in Plants Plants

vesicles move to equator line up & fuse to form 2 membranes = cell plate derived from Golgi

new cell wall is laid down between membranes new cell wall fuses

with existing cell wall

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Cytokinesis in plant cell

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Mitosis in plant cell

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onion root tip