Warm Up (take out your homework)

• Draw 5 boxes

• Draw the process of mitosis in each phase, and describe what is happening to the DNA in each phase

Interphase EarlyMitosis

Mid-Mitosis

LateMitosis

FinalProduct

Assessment

• Next Class: Growth and Development

Development: Growth & Differentiation Essential Questions

• How are the bodys tissues and organs formed?

• How can developmental problems lead to cancer?

• How are technologies like stem cell therapies and cloning organisms related to developmental processes?

Todays Objectives

• Describe the role of differentiation in the development of a multicellular organism.

• Describe the process that leads to differentiation of cells in a multicellular organism.

• Review key concepts of the unit so far (growth & differentiation)

Concept Review

Development

Growth

Mitosis

Differentiation

Inside Influences

Outside Influences (Induction)

Senescence

Vocab

• Zygote: a fertilized egg

• Phenotype: the observable traits of an organism

Readings: Coordinating GrowthDifferentiation and the Expression of Genetic Info

1) What might happen if too little cell division takes place? – Injuries go unrepaired

2) Too much?– A tumor can develop

2) Most of us go through every stage in the same sequence.

So what?

So clearly there is some pretty good coordination of development going on.

3) What are the two possible explanations for why all cells with the same DNA don’t do the same thing?

**DIFFERENTIAL GENE EXPRESSION**– Environments inside the cells differ. A substance in

one part of the cytoplasm ends up in one daughter cell and not the other. This may change the activity of the genes in that cell.

– Something outside the cell differs. A nearby cell may affect its neighbor’s gene expression.

4) Define induction and give an example.An outside influence on differentiation that occurs when a group of cells can cause a neighboring group of cells to differentiate in a certain way.

Example: eye tissue developmentSweat glands, teeth, limbs, and feathers

* See graphic

5) Why are we not 4 Foot wide brains?

-Different cell types use different parts of their genetic material

6) How do environmental influences affect gene expression ?-Although all cells have the same genes, environmental influences inside and outside the cell cause certain genes to turn on and others to turn off.

*Active gene is transcribed to mRNA for protein synthesis

*Inactive gene is not transcribed

VOCAB GAME

• Try to get your partner to guess the vocabulary word by giving him or her the definition.

Development Differential Gene ExpressionGrowth InterphaseDifferentiation MitosisInduction Senescence

Concept Review

Development: Continuous permanent

changes from fertilization to death

Growth: Increase in number of cells

Mitosis: Cell division

Differentiation: Changes in structure and function of cells

Inside Influences Outside Influences (Induction)

Senescence: Aging leading to an

irreversible loss in function

Growth• Growth is a key

component of development in which a multicellular organism increases in size due to an increase in the number of cells.

• Mitosis produces an increase in the number of cells during development.

(http://geneticssuite.net/files/Cell%20multiplication.jpg)

The Cell Cycle – Life of a Cell

• Interphase– Accounts for 90% of the life cycle of a cell– Cell metabolism is active, the cell grows and DNA isreplicated before the cell divides

• M Phase– Consists of Mitosis (division of the nucleus) and Cytokinesis (division of the cytoplasm)

Mitosis results in how many daughter cells?

A) 1B) 2C) 3D) 4

How do the daughter cells of mitosis compare with the parent cell genetically?

A) differentB) sameC) some parts are different, some parts are the

sameD) I’m not sure

DNA packaging in a eukaryotic cell

• DNA wraps around proteins called histones to form chromatin fibers. Chromatin is the form in which genetic material takes during interphase.

• Chromatin further condenses into a chromosome during the M phase of the cell cycle.

(http://www.tutorvista.com/biology/types-of-chromosomes)

Chromosome Structure• A duplicated chromosome

consists of two sister chromatids (present during prophase and metaphase of mitosis)

• Sister chromatids are joined at a centromere– Which is an attachment point

for spindle fibers during mitosis

• A chromosome consists of one chromatid after sister chromatids are pulled apart during mitosis

Chromososmes are present in a condensed, visible (under the microsccope) form during

A) All parts of the cell cycleB) Interphase onlyC) Mitosis onlyD) I’m not sure

Interphase • Includes:

• Growth of cell• Metabolism is active• DNA is replicated• “Spaghetti Stage”

Early Mitosis

• Chromosomes Condense• Nuclear envelope

(membrane) disintegrate• Centrosomes migrate to

poles• Spindle fibers appear

Mid-Mitosis

• Chromosomes line up along the equator (middle) of the cell

Late Mitosis

• Sister chromatids separate

• Spindle fibers pull chromosomes to poles

Final Result: 2 identical daughter cells

• Chromosomes go to separate poles

• Chromosomes unwind• Nuclear envelope

reforms• Cytokinesis

(cytoplasm division) is completed

2.1.

4.3.

Differentiation• During development,

differentiation is the process by which cells become specialized. In other words, cells become structurally and functionally different.

• Different cell types express (make proteins from) different genes within the DNA sequence of the nucleus.

(http://scienceblogs.com/clock/2006/12/from_two_cells_to_many_cell_di.php)

How does differentiation occur?• During development of an embryo, both the

internal environment of cells and the external environment of cells within the embryo differs.

• This causes individual cells within the embryo to turn certain genes on and others off.

• Genes become turned on when they are transcribed into mRNA for protein synthesis.

• Different cell types produce certain proteins that are specific to the functioning of that cell type.

T-R-I summarizationsDraw two 4-squares on one sheet of paper

T-R-I summarizations

Topic: Growth Restriction

Illustration Non-illustration

T-R-I summarizations

Topic: Differentiation Restriction

Illustration Non-illustration

Written Response

• Write a one paragraph response to the following question:– Explain the relationship between mitosis and

growth that occurs during development

– Remember: more depth = higher grade

Four-Two-One

• Test prep for next class– Differentiation

Written Response

• Write a one paragraph response to the following question:

–Compare and contrast growth, differentiation, and senescencel

–Remember: more depth = higher grade