Chapter 5, 6.1, & 6.2: Cell Growth and

Division

KEY CONCEPT : Cells have distinct phases of growth, reproduction, and normal functions.

5.1 The Cell Cycle

Cell Reproduction

“All cells come from pre-existing cells”Two main types of cell reproduction:

◦Asexual: (MITOSIS) – offspring is identical to the parent cell

◦Sexual: (MEIOSIS) – offspring is not identical to either parent

◦produces gametes (sperm and egg cells)

The Cell Cycle

The complete series of events from one cell division to the next.

Why Do Cells Divide?◦Reproduction: new organisms are produced

from parents◦Growth: multicellular organisms grow by

producing more cells ◦Repair: damaged cells are replaced by

producing new cells

The cell cycle is a regular pattern of growth, DNA replication, and cell division.

– Interphase: Longest phase of the cell cycle– Gap 1 (G1): cell growth and

normal functions– DNA synthesis (S): copies DNA– Gap 2 (G2): additional growth

and prepares for division– Mitosis (M): includes division of

the cell nucleus (mitosis) and division of the cell cytoplasm (cytokinesis)– Prophase– Metaphase– Anaphase– Telophase

The cell cycle has four main stages.

Overview of the Cell Cycle.url

CELL CYCLE OVERVIEW

Put it all together!

1. What are the stages of cell cycle?◦ G1, S, G2, and Mitosis

2. What happens during G1?◦ Cell grows

3. What happens during S?◦ Replication of DNA

4. What happens during G2?◦ Cell Prepares to divide

5. What happens during M?◦ Cell divides

Cells divide at different rates.The rate of cell division varies with the need for

those types of cells.Also, cells divide at different rates depending on

person’s age.Some cells are unlikely to divide (G0).

Cell size is limited. A cell must be big enough to fit all the molecules and

organelles it needs to live. It also must be small enough to quickly transport

nutrients and wastes into and out of the cell. As a cell gets bigger, its volume increases faster than

its surface area.

Surface area must allow for adequate exchange of materials.

– Cell growth is coordinated with division.

– Cells that must be large have unique shapes.

KEY CONCEPT : Cells divide during mitosis and cytokinesis.

5.2 Mitosis and Cytokinesis

Chromosomes condense at the start of mitosis.

DNA doublehelix

DNA andhistones

Chromatin

SupercoiledDNA

Each continuous ,double-stranded DNA molecule makes one chromosome.

DNA wraps around proteins called histones, forming chromatin.

Interactions between parts of the histones further compact the DNA

The chromatin coils more and more tightly around organizing proteins.

DNA plus proteins is called chromatin.

• One half of a duplicated chromosome is a chromatid.

• Sister chromatids are held together at the centromere.

• Telomeres (far ends of each chromatid) protect DNA and do not include genes.

Condensed, duplicated chromosome

chromatidtelomere

centromere

telomere

Telomeres and Aging The Science of Aging

http://www.youtube.com/watch?v=x1zw6uRxKYUhttp://www.youtube.com/watch?v=BkcXbx5rSzw

Cancer Risk With Telomere Length

http://www.youtube.com/watch?v=PylY3hVzrb4

Parent cell

centrioles

spindle fibers

centrosome

nucleus withDNA

Longest phase of cell cycle

Interphase has 3 stages: ◦G1, S, & G2

The cell contains a pair of centrioles.

The cell's chromosomes have duplicated but are in the form of chromatin.

Interphase

Mitosis produces 2 genetically identical daughter cells.

Mitosis divides the cell’s nucleus in four phases.◦Prophase◦Metaphase◦Anaphase◦Telophase

I remember it as PMAT

Mitosis

1) Prophase: o The nuclear membrane begins to

disappearo chromosomes condense into

chromosomeso spindle fibers form

2) Metaphase:o Spindle fibers attach to centromereso Spindle fibers line up chromosomes in the

middle of the cell.

3) Anaphase:o spindle fibers condense and separate sister

chromatids to opposite sides of the cell.

4) Telophase:o chromosomes begin to uncoilo the nuclear membrane reformso the spindle fibers disappearo Cytokinesis, which divides the cell in two,

begins.

Cytokinesis

– Divides cytoplasm between 2 daughter cells each with genetically identical cells.

– Cytokinesis differs in animal and plant cells

– In animal cells, cleavage furrow separates two new nuclei

– In plant cells, a cell plate forms.

Cytokinesis: Animal Cells & Plant Cells

Mitosis

What stage is this?

What stage is this?

What stage is this?

What stage is this?

What stage is this?

Mitosis

http://www.youtube.com/watch?v=1cVZBV9tD-A

Elodea cells

Cheek cells

Onion Cell Mitosis

KEY CONCEPT: Cell cycle regulation is necessary for healthy growth.

5.3 Regulation of the Cell Cycle

Internal and external factors regulate cell division.

External factors include physical and chemical signals.Growth factors are proteins that stimulate cell division.

◦Most mammal cells form a single layer in a culture dish and stop dividing once they touch other cells.

◦a normal feature of healthy organisms◦caused by a cell’s production of self-destructive

enzymes◦a mechanism by which organisms limit the growth and

replication of cells. ◦loss of apoptosis is one of the key mechanisms behind

cancer.

Apoptosis is programmed cell death.

PICTURE: http://www.brecorder.com/world/north-america/104165-half-of-world-countries-unprepared-to-deal-with-cancer-who.html

Cell division is uncontrolled in cancer.

Cancer cells form disorganized clumps called tumors.

cancer cellbloodstream

normal cell

– Benign tumors – Remain clustered and can be removed.– Remain at the original site

– Malignant tumors – metastasize, or break away, and can form more tumors.– Spread in the body

Cancer cells do not carry out necessary functions.

• Cancer cells come from normal cells with damage to genes involved in cell-cycle regulation.

Carcinogens are substances known to promote cancer.

Carcinogens - College Biologyhttp://

www.youtube.com/watch?v=9-I3kKYY7zE

Cancer Treatment• Surgery: Remove tumor(s)• Radiation & Chemotherapy: used to disrupt

cell division– May have undesirable side effects

• Standard cancer treatments typically kill both cancerous and healthy cells

FYI: Number of deaths for leading causes of death

1. Heart disease: 597,689 Risk factors: obesity, smoking, high blood pressure & cholesterol, and diabetes

2. Cancer: 574,743 Lung cancer causes the most deaths among men & women, followed in women by breast cancer

3. Chronic lower respiratory diseases: 138,080 smoking & second hand smoking

4. Stroke: 129,476 Risk factors: alcohol, smoking, obesity, high blood pressure & cholesterol, and diabetes

• Occurs when the blood supply to an area of the brain is obstructed, causing brain cells to die

5. Accidents (unintentional injuries): 120,8596. Alzheimer's disease: 83,494 It’s genetics; memory problems

7. Diabetes: 69,071 Risk factors: obesity, old age, a family history of diabetes and not exercising

• abnormally high blood sugar levels, and can lead to kidney failure, blindness, heart disease

8. Nephritis and nephrotic syndrome: 50,476• Nephritis is the inflammation of the kidneys• Nephrotic syndrome is caused by different disorders that damage

the kidneys

9. Influenza and Pneumonia: 50,097 caused by a virus; A seasonal flu shot can help prevent it

10. Intentional self-harm (suicide): 38,364

THE TEN LEADING CAUSES OF DEATH

What is cancer?

http://www.youtube.com/user/1cancercenter?v=SGaQ0WwZ_0I

Cancer Treatments: Radiation & Chemotherapy

http://www.youtube.com/watch?v=yrR_s0UzS1M

KEY CONCEPT: Many organisms reproduce by cell division.

5.4 Asexual Reproduction

Binary fission is similar in function to mitosis.

Asexual reproduction is the creation of offspring from a single parent.◦Binary fission produces two daughter cells

genetically identical to the parent cell.◦Binary fission occurs in

prokaryotes.

parent cell

DNA duplicates

cell begins to divide

daughter cells

KEY CONCEPT: Cells work together to carry out complex functions.

5.5 Multicellular Life

Multicellular organisms depend on interactions among different cell types.

Tissues are groups of cells that perform a similar function.

Organs are groups of tissues that perform a specific or related function.

Organ systems are groups of organs that carry out similar functions.

CELL TISSUE ORGAN

vascular tissue

leaf

stem

lateralroots primary

root

SYSTEMS

root

syste

msh

oot

syste

m

Lung cell Lung tissue Lung Respiratory System Person

cells tissue organ organ system organism

cells tissues

organs

organ system

Specialized cells perform specific functions.Cells develop into their mature forms through the

process of cell differentiation.Cells differ because different combinations of genes

are expressed.A cell’s location in an embryo helps determine how it

will differentiate.

Outer: skin cells Middle: bone cells Inner: intestines

Stem cells are unique body cells.

Stem cells have the ability to◦divide and renew themselves◦remain undifferentiated in form◦develop into a variety of specialized cell types

First, an egg is fertilized by a sperm cell in a petri dish. The egg divides, forming an inner cell mass. These cells are then removed and grown with nutrients. Scientists try to control how the cells specialize by adding or removing certain molecules.

Stem cells come from adults and embryos.– Adult stem cells can be hard to isolate and grow.– The use of adult stem cells may prevent transplant rejection.– The use of embryonic stem cells raises ethical issues– Embryonic stem cells can be grown indefinitely in culture.

The use of stem cells offers many currently realized and potential benefits.– Stem cells are used to treat leukemia and lymphoma.– Stem cells may cure disease or replace damaged organs.– Stem cells may revolutionize the drug development process.

Trachea Grown With Stem Cells

http://www.youtube.com/watch?v=XL72Dn3rJ_E

http://www.youtube.com/watch?v=49YputwJ6YM

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

Stem cells in bone marrow are being used to treat EBhttp://www.youtube.com/watch?v=F8DLVTR1iiQ

Bone Marrow Transplant-Mayo Clinichttp://www.youtube.com/watch?v=GIy2nMnuGGI

KEY CONCEPT: Gametes have half the number of chromosomes that body cells have.

6.1 Chromosomes and Meiosis

You have body cells and gametes. Body cells are also called somatic cells.Sex cells (germ cells) are called gametes.

◦Sex cells are located in the ovaries and testes.◦Gametes are sex cells: egg and sperm.◦Gametes have DNA that can be passed to offspring.

body cells sex cells (sperm) sex cells (egg)

• Your body cells have 23 pairs of chromosomes.– Homologous pairs of

chromosomes have the same structure.

– For each homologous pair, one chromosome comes from each parent.

• Chromosome pairs 1-22 are autosomes.

• Sex chromosomes, X and Y, determine gender in mammals.– Females: XX – Males: XY

Your cells have autosomes and sex chromosomes.

Common Name Diploid numbers (2n)

Human 46

Donkey 42

Dog 78

Cat 38

Mouse 40

Frog 26

Fruit fly 8

Corn 20

Potato 48

Yeast 32

Mold 4

Body cells are diploid; gametes are haploid.

Fertilization between egg and sperm occurs in sexual reproduction.

Diploid (2n) cells have two copies of

every chromosome.◦ Body cells are diploid.◦ Half the chromosomes come from each

parent.

• Haploid (n) cells have one copy of every chromosome.– Gametes are haploid.– Gametes have 22 autosomes and 1 sex

chromosome.

• Meiosis makes haploid cells from diploid cells. – Meiosis occurs in sex cells. – Meiosis produces gametes.

KEY CONCEPT : During meiosis, diploid cells undergo two cell divisions that result in haploid cells.

6.2 Process of Meiosis

Cells go through two rounds of division in meiosis. Meiosis reduces chromosome number and creates

genetic diversity.

Meiosis I and meiosis II each have four phases, similar to those in mitosis.

homologous chromosomes

sisterchromatids

sisterchromatids

– Pairs of homologous chromosomes separate in meiosis I.

– Homologous chromosomes are similar but not identical.

– Sister chromatids divide in meiosis II.– Sister chromatids are copies of the same

chromosome.

Meiosis I• occurs after DNA has been replicated.• divides homologous chromosomes in four phases.

Meiosis II• divides sister chromatids in four phases• DNA is not replicated between meiosis I

and meiosis II.

• Meiosis differs from mitosis in significant ways.– Meiosis has two cell divisions while mitosis has

one.– In mitosis, homologous chromosomes never pair

up.– Meiosis results in haploid cells; mitosis results

in diploid cells.

Haploid cells develop into mature gametes.

Gametogenesis is the production of gametes which differs between females and males.– Sperm primarily contribute DNA to

an embryo.– Eggs contribute DNA, cytoplasm,

and organelles to an embryo.– During meiosis, the egg gets most

of the contents; the other cells form polar bodies.

FYI Unlike men, who produce new sperm daily throughout most of their

lifetime, women are born with all their eggs in their ovaries. To be more precise, a woman is born with about one to two million immature eggs, or follicles, in her ovaries.

Throughout her life, the vast majority of follicles will die. When a woman reaches puberty and starts to menstruate, only about 400,000 follicles remain. With each menstrual cycle, a thousand follicles are lost and only one lucky little follicle will actually mature into an egg, which is released into the fallopian tube, kicking off ovulation. That means that of the one to two million follicles, only about 400 will ever mature.

Relatively little or no follicles remain at menopause, which usually begins when a woman is between 48-55 years of age. The remaining follicles are unlikely to mature and become viable eggs because of the hormonal changes that come along with menopause.

Meiosis

http://www.youtube.com/watch?v=rB_8dTuh73c

The Cell cycle (5 min)http://www.learn360.com/ShowVideo.aspx?ID=253783&SearchText=cell+cycle&MediaFormat=3360063Mitosis video Quiz (Full Video: 20 min)http://www.learn360.com/ShowVideo.aspx?ID=253781&SearchText=mitosis&MediaFormat=3360062Mitosishttp://wps.prenhall.com/wps/media/objects/486/498658/CDA8_2/CDA8_2a/CDA8_2a.htmMitosis Rap - http://www.nclark.net/MitosisRap.mp3http://www.loci.wisc.edu/outreach/bioclips/CDBio.html

Mitosis.url

Video I don’t usually show these videos, but they are on here just in case you want to use them.

Meiosis Video Quiz (25 min)http://www.learn360.com/ShowVideo.aspx?ID=132394&SearchText=meiosis&MediaFormat=3360062

What is Meiosis?http://www.learn360.com/ShowVideo.aspx?ID=149053&SearchText=cell+cycle&MediaFormat=3360063

Mitosis and Meiosis Animationhttp://www.lewport.wnyric.org/jwanamaker/animations.htm

Sexual reproduction (30 minutes)http://www.learn360.com/ShowVideo.aspx?ID=131941&SearchText=reproduction&MediaFormat=3360062

Video I don’t usually show these videos, but they are on here just in case you want to use them.