cell division chapter 9 lecture outline. © 2009 w.w. norton & company, inc. discover biology...

Cell Division

Chapter 9 Lecture Outline

© 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 2

The Need for Cell Division Renewal and repair of tissues

Stem cells capable of self-renewal give rise to descendant cells

Asexual and sexual reproduction Prokaryotes divide through binary fission Eukaryote cell division is more complicated


Cell cycle: Two Main Stages Cell cycle

Series of events in life cycle of a cellTime to complete cell cycle

Dependent on organism, type of cell, life stage

Two main stages Interphase

Most cells spend 90% of lifespan in this stage

Cell division Mitosis and cytokinesis


Interphase: The Longest Stage

The period between divisionsLongest phase of the cell cycleThe cell prepares to divide

Divided into 3 stages: G1: growth after mitosis

S: synthesis of DNA

G2: growth before mitosis


The Cell Cycle

G1 and G2 phases

G stands for “gap”Early biologists saw a gap

Between S phase and cell division

Important for two reasons periods of growth

size of cell and protein content increase

preparation for next phase checkpoint that ensures conditions are suitable



G0 Phase

Most cells are not actively dividing

These cells are in G0 phaseCan last days to years Some cells will divide again; e.g.

liver cells Some cells stay in G0; e.g. nerve

cells


DNA Packaged as Chromosome DNA molecules are enormously long

Double helix nearly 2 meters in length DNA is tightly packaged with proteins Chromatin

DNA and proteins Chromosome

Tightly packed


KaryotypeChromosomes are

visible during mitosis

Their number and shape can be studied

Humans have 46 chromosomes


Homologous Chromosomes 46 chromosomes are arranged in 23

pairs One came from each parent

22 pairs are autosomes Both chromosomes are homologues

1 pair are sex chromosomes Can be homologous; XX for females Can be different; XY for males


Mitosis Consists of five phases

Prophase Prometaphase Metaphase Anaphase Telophase

Cytokinesis: division of the cytoplasm


Prophase

Cell enters mitosis Chromosomes condense Centrosomes move apart

Go to the poles of the cell

Mitotic spindle begins to form


Prometaphase Mitosis proceeds

Chromosome condensation completedNuclear envelope breaks downMitotic spindle extends from centrosomes

Attaches to centromeres of chromosomes Kinetochore: site of attachment Chromatids linked to opposite poles


Metaphase

Chromosomes line up Metaphase plate Align sister chromatids

Equal and balanced segregation


Anaphase

Chromatids separateBreak free and dragged

to opposite sides

Microtubules shorten Result:

Equal segregation of chromosomes in two daughter cells


Telophase and Cytokinesis Telophase:

Chromosomes reach the poles Mitotic spindle falls apart Chromosomes unfold Nuclear membrane reforms

CytokinesisCytoplasm is dividedTwo cells are formed


Mitosis


Meiosis

Used to make gametes Eggs and sperm

Chromosome number is halved (haploid)

Zygote is diploid after fertilization

Meiosis

Fertilization

Mitosis


Meiosis I vs. Mitosis

Sister Chromatids separate

Sister Chromatids remain attached


Meiosis II

Metaphase Anaphase


Which of the following is not true about interphase?

A. The cell grows larger during interphase.

B. Chromosomes are duplicated during interphase.

C. Interphase is divided into three phases.

D. Chromosomes segregate to daughter cells during interphase.

Concept Quiz


Which of the following is true about

homologous chromosomes?

A. Both were received from the same parent.

B. One of each segregates to each daughter cell

during mitosis.

C. Both stay together in meiosis I.

D. All 23 pairs are always homologous.

Concept Quiz


Meiosis insures that

A. Each gamete receives the same genes

B. Chromosome number is doubled in the gametes

C. Zygotes produced by fertilization have the normal number of chromosomes

D. All paternal chromosomes end up in the same gamete

Concept Quiz

Biology In the News

“New Type of Stem Cells May Help Regenerate Heart Tissues” Induced pluripotent stem cells

A genetically reprogrammed adult body cell Behaves like pluripotent embryonic stem cells


TermsChromatin

Chromosome

Crossing-over

Cytokinesis

Diploid

DNA segregation

Fertilization

G0 phase

G1 phase

G2 phase

Gametes

Genetic recombination

Haploid

Homologous pair

Homologues

Independent assortment

Interphase

Karyotype


TermsKinetochores

Maternal homologue

Meiosis

Meiosis I

Meiosis II

Metaphase

Mitosis

Mitotic spindle

Paternal homologue

Prometaphase

Prophase

S phase

Sex chromosomes

Sexual reproduction

Sister chromatids

Somatic cells

Stem cells

Telophase



Process Animation 9.1The Cell Division Cycle

Macintosh

Windows


Process Animation 9.2Mitosis and Cell Division

Macintosh

Windows


Process Animation 9.3Meiosis

Macintosh

Windows

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Additional Art from Chapter 9

All art files from the book are available in JPEG and PPT formats on the

Instructor Resource Disc

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cell division chapter 9 lecture outline. © 2009 w.w. norton & company, inc. discover biology...

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