Development by Mr. Charlton & Ms. Hogan Lebanon High School

DEVELOPMENT: MATH IS EVERYWHERE DEVELOPMENT = Growth + Differentiation DEVELOPMENT = Growth + Differentiation

Components of Development Growth - The process of a multicellular organism increasing its number of cells, becoming larger. (i.e. zygote to an adult) Growth - The process of a multicellular organism increasing its number of cells, becoming larger. (i.e. zygote to an adult) Differentiation - The process of cells in a multicellular organism (initially all alike) becoming different from each other generating the various tissues (i.e. nerve, muscle, skin and bone, etc.) necessary to be a functional adult. Differentiation - The process of cells in a multicellular organism (initially all alike) becoming different from each other generating the various tissues (i.e. nerve, muscle, skin and bone, etc.) necessary to be a functional adult.

Thoughts on development: Growth Cells generating more cells (Mitosis and Cytokinesis) (asexual reproduction) Cells generating more cells (Mitosis and Cytokinesis) (asexual reproduction) A single cell has size limits, (limited by physics) therefore for organisms to become larger they must be multicellular. A single cell has size limits, (limited by physics) therefore for organisms to become larger they must be multicellular. All cells of an organism have a complete set of DNA to make the entire organism. All cells of an organism have a complete set of DNA to make the entire organism. Cell death, as well as cell growth must occur for proper development Cell death, as well as cell growth must occur for proper development Connected to the cell cycle. Connected to the cell cycle.

Review Mitosis vs Meiosis Cell division for reproduction for growth (in multi-cellular forms) Cell division for reproduction for growth (in multi-cellular forms) Chromosome number is kept constant from parent cells to daughter cells (one cell 2N- >2 cells each 2N) Chromosome number is kept constant from parent cells to daughter cells (one cell 2N- >2 cells each 2N) All non-gamete cells All non-gamete cells Part of cell cycle Part of cell cycle Cell division for sexual reproduction (gametes) Cell division for sexual reproduction (gametes) Chromosome number is reduced (2n-> 1N cells) Chromosome number is reduced (2n-> 1N cells) Only occurs to make gametes Only occurs to make gametes Occurs in testes and ovaries Occurs in testes and ovaries

Cell cycle

Cytokinesis-rest of the cell divides

Phases of Mitosis Interphase Interphase Prophase Prophase Metaphase Metaphase Anaphase Anaphase Telophase Telophase Animation link(s) cytokinesis_files/frame.htm#slide0020.htm

Interphase

Prophase

Metaphase

Anaphase

Telophase

Then cytokinesis again!!! Entire cell cycle repeats with the newly formed cells.

Thoughts on development: Differentiation What if your entire body was made of only stem cells? Muscle cells? Nerve cells? What if your entire body was made of only stem cells? Muscle cells? Nerve cells? Do different types of cells (tissue) perform different jobs in a multicellular organism? Do different types of cells (tissue) perform different jobs in a multicellular organism? If all of the organisms cells are genetically Identical, how do they become different types of cells (tissue)? If all of the organisms cells are genetically Identical, how do they become different types of cells (tissue)?

Epithelial and Connective

Nerve and Muscle

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

DEVELOPMENT: MATH IS EVERYWHERE DEVELOPMENT = Growth + Differentiation DEVELOPMENT = Growth + Differentiation

Components of Development Growth - The process of a multicellular organism increasing its number of cells, becoming larger. (i.e. zygote to an adult) Growth - The process of a multicellular organism increasing its number of cells, becoming larger. (i.e. zygote to an adult) Differentiation - The process of cells in a multicellular organism (initially all alike) becoming different from each other generating the various tissues (i.e. nerve, muscle, skin and bone, etc.) necessary to be a functional adult. Differentiation - The process of cells in a multicellular organism (initially all alike) becoming different from each other generating the various tissues (i.e. nerve, muscle, skin and bone, etc.) necessary to be a functional adult.

Historical perspective The “Homunculus” Theory A fully formed person, just very tiny, exists in the head of a sperm cell. The egg makes no contribution except to function as an incubator. A fully formed person, just very tiny, exists in the head of a sperm cell. The egg makes no contribution except to function as an incubator. No differentiation necessary!!!!!!!!!! We now know better…

Embryonic differentiation: Zygotes

Early embryonic development

Morula

Blastula

Gastrulation

It is not birth, marriage, or death, but gastrulation, which is truly the most important time in your life." Lewis Wolpert (1986)

Embryonic cell (tissue) types As embryo’s develop to the gastrulation stage they form three basic types of tissue which differentiate into all other tissues: As embryo’s develop to the gastrulation stage they form three basic types of tissue which differentiate into all other tissues: Endoderm Endoderm Mesoderm Mesoderm Ectoderm Ectoderm

These basic tissues become:

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

Influences on differentiation (switching genes on and off) Environmental influences both inside the cell and outside the cell can cause certain genes to switch on or off at appropriate or inappropriate times. Environmental influences both inside the cell and outside the cell can cause certain genes to switch on or off at appropriate or inappropriate times. Inside the cell- differential distribution of materials during cell division can cause cells to develop differently. Inside the cell- differential distribution of materials during cell division can cause cells to develop differently. Outside the cell- chemical communication with nearby cells may influence development based on strength of signal. Outside the cell- chemical communication with nearby cells may influence development based on strength of signal. Induction- is a special type of outside influence. Induction- is a special type of outside influence. ??????????? (good field for a career) ??????????? (good field for a career)

Induction!!!

Homeobox Master control genes that other genes relating to very complex patters of development. Master control genes that other genes relating to very complex patters of development. Gene sequences found in common among organsms. Gene sequences found in common among organsms. Evolution solves the really complex problems only once. Evolution solves the really complex problems only once.

apoptosis (cell death) apoptosis (cell death)

Apoptosis (cell death) at the appropriate time is also very vital to development.

What next?

Development sometimes messes up! Cancer- one’s own cells fail to stop reproducing when they should. Cancer- one’s own cells fail to stop reproducing when they should. Birth defects- environmental factors + genetics cause misinformation during development. Birth defects- environmental factors + genetics cause misinformation during development.

Key Development terms Zygote Zygote Blastula Blastula Gastrulation Gastrulation Growth Growth Cytokinesis Cytokinesis Mitosis Mitosisinterphaseprophasemetaphaseanaphasetelophase Differentiation Differentiation Senescence Senescence Cell cycle Cell cycle DNA DNA Induction Induction Cancer Cancer Metastasis Metastasis Birth defects Birth defects Mutation Mutation

Final thoughts Development must occur at the correct times and correct places in the embryo. Development must occur at the correct times and correct places in the embryo. Animal development occurs in consistent patterns. Animal development occurs in consistent 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 abortions (in humans the rate is approx. 25+%). Developmental errors often cause spontaneous abortions (in humans the rate is approx. 25+%). Environmental factors can greatly influence development (especially during very early development). Environmental factors can greatly influence development (especially during very early development). Development = growth + differentiation. Development = growth + differentiation. Genes can also switch other genes on or off, creating a cascade (ripple effect). Genes can also switch other genes on or off, creating a cascade (ripple effect). Homeobox genes are master control genes. Homeobox genes are master control genes. We still have a lot to learn about development. We still have a lot to learn about development.

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