DevelopmentDevelopment

Links - BiologyLinks - Biology

Components of Components of DevelopmentDevelopment

GrowthGrowth- The process of a - The process of a multicellular increasing its number of multicellular increasing its number of cells, becoming larger. (i.e. zygote to cells, becoming larger. (i.e. zygote to an adult) an adult)

DifferentiationDifferentiation- The process of - The process of cells in a multicellular organism cells in a multicellular organism (initially all alike) becoming different (initially all alike) becoming different from each other generating the from each other generating the various tissues (i.e. nerve, muscle, various tissues (i.e. nerve, muscle, skin and bone, etc.) necessary to be a skin and bone, etc.) necessary to be a functional adult .functional adult .

Thoughts on development:Thoughts on development:GrowthGrowth

Cells generating more cells (Mitosis and Cells generating more cells (Mitosis and Cytokinesis)Cytokinesis)

A single cell has size limits, therefore for A single cell has size limits, therefore for organisms to become larger they must be organisms to become larger they must be multicellular.multicellular.

All cells of an organism have a complete All cells of an organism have a complete set of DNA to make the entire organism.set of DNA to make the entire organism.

Cell death, as well as cell growth must Cell death, as well as cell growth must occur for proper developmentoccur for proper development

Connected to the cell cycle.Connected to the cell cycle.

Mitosis and CytokinesisMitosis and Cytokinesis

Cell cycleCell cycle

Phases of MitosisPhases of Mitosis InterphaseInterphase ProphaseProphase MetaphaseMetaphase AnaphaseAnaphase TelophaseTelophase

Animation link(s)Animation link(s)

http://science.nhmccd.edu/biol/mitosis/pmitosis.htmlhttp://science.nhmccd.edu/biol/mitosis/pmitosis.html

http://www.lewport.wnyric.org/jwanamaker/animations/http://www.lewport.wnyric.org/jwanamaker/animations/mitosis.htmlmitosis.html

http://www.sci.sdsu.edu/multimedia/mitosis/mitosis_qt1http://www.sci.sdsu.edu/multimedia/mitosis/mitosis_qt1.html.html

InterphaseInterphase

ProphaseProphase

MetaphaseMetaphase

AnaphaseAnaphase

TelophaseTelophase

Thoughts on development:Thoughts on development:DifferentiationDifferentiation

What if your entire body was made of only What if your entire body was made of only stem cells? Muscle cells? Nerve cells?stem cells? Muscle cells? Nerve cells?

Do different types of cells (tissue) perform Do different types of cells (tissue) perform different jobs in a multicellular organism?different jobs in a multicellular organism?

If all of the organisms cells are genetically If all of the organisms cells are genetically Identical, how do they become different Identical, how do they become different types of cells (tissue)?types of cells (tissue)?

Epithelial and ConnectiveEpithelial and Connective

Nerve and MuscleNerve and Muscle

OKAY???????OKAY???????

But how does an But how does an organism get all of organism get all of these cell (tissue) these cell (tissue)

types?types?

Historical perspectiveHistorical perspective

The “Homunculus” Theory The “Homunculus” Theory = A fully formed = A fully formed person, just very tiny, person, just very tiny, exists in the head of a exists in the head of a sperm cell. The egg sperm cell. The egg makes no contribution makes no contribution except to function as except to function as an incubator.an incubator.

No differentiation No differentiation necessary!!!!!!!!!! necessary!!!!!!!!!!

We now know better.We now know better.

Embryonic differentiation:Embryonic differentiation:ZygotesZygotes

Early embryonic Early embryonic developmentdevelopment

BlastulaBlastula

GastrulationGastrulation

It is not birth, marriage, It is not birth, marriage, or death, but or death, but

gastrulation, which is gastrulation, which is truly the most important truly the most important

time in your life."time in your life."                       

Lewis Wolpert (1986) Lewis Wolpert (1986)

Embryonic cell (tissue) Embryonic cell (tissue) typestypes

As embryo’s As embryo’s develop to the develop to the gastrulation gastrulation stage they form stage they form three basic three basic types of tissue types of tissue which which differentiate into differentiate into all other tissues:all other tissues:

EndodermEndoderm MesodermMesoderm EctodermEctoderm

These basic tissues become:These basic tissues become:

OKAY ??OKAY ??

But how do we get to But how do we get to become these tissues become these tissues from embryonic stem from embryonic stem

cells?cells?

Influences on differentiationInfluences on differentiation(switching genes on and off)(switching genes on and off)

Environmental influences both inside the cell and Environmental influences both inside the cell and outside the cell can cause certain genes to switch outside the cell can cause certain genes to switch on or off at appropriate or inappropriate times.on or off at appropriate or inappropriate times.

Inside the cell- differential distribution of materials Inside the cell- differential distribution of materials during cell division can cause cells to develop during cell division can cause cells to develop differently.differently.

Outside the cell- chemical communication with Outside the cell- chemical communication with nearby cells may influence development based on nearby cells may influence development based on strength of signal.strength of signal.

Induction- is a special type of outside influence. Induction- is a special type of outside influence. (Leads to Cell Differentiation)(Leads to Cell Differentiation)

??????????? (good field for a career)??????????? (good field for a career)

Induction!!!Induction!!!

ApoptosisApoptosis (cell death) at the (cell death) at the appropriate time is also very vital to appropriate time is also very vital to

development.development.

What next?What next?

Development sometimes messes Development sometimes messes up!up!

CancerCancer- one’s own cells fail to - one’s own cells fail to stop reproducing when they stop reproducing when they should.should.

Birth defects-Birth defects- environmental environmental factors + genetics cause factors + genetics cause misinformation during misinformation during development.development.

Key Development termsKey Development terms ZygoteZygote BlastulaBlastula GastrulationGastrulation GrowthGrowth CytokinesisCytokinesis MitosisMitosis

interphaseinterphase

prophaseprophase

metaphasemetaphase

anaphaseanaphase

telophasetelophase

DifferentiationDifferentiation SenescenceSenescence Cell cycleCell cycle DNADNA InductionInduction CancerCancer MetastasisMetastasis Birth defectsBirth defects MutationMutation

Final thoughts Final thoughts Development must occur at the correct times and Development must occur at the correct times and

correct places in the embryo.correct places in the embryo. Animal development occurs in consistent Animal development occurs in consistent

patterns.patterns. Plants go through similar development.Plants go through similar development. Cell deaths must also occur at appropriate times.Cell deaths must also occur at appropriate times. Development is a zygote to death process.Development is a zygote to death process. Developmental errors often cause spontaneous Developmental errors often cause spontaneous

abortions (miscarriage) abortions (miscarriage) Environmental factors can greatly influence Environmental factors can greatly influence

development (especially during very early development (especially during very early development).development).

Development = growth + differentiation.Development = growth + differentiation. We still have a lot to learn about development.We still have a lot to learn about development.