Zygote: fertilized cell created by the union of the egg and sperm Zygote divides into Embryonic stem cells –Potential to become any type of cell Average.

• Zygote: fertilized cell created by the union of the egg and sperm

• Zygote divides into Embryonic stem cells– Potential to become

any type of cell

• Average human:– 100 trillion cells– Over 200 types of

human cells23

chromosomes

Egg Cell

23 chromosomes

zygoteEmbryonic Stem cells

Stem cell controversy• Stem cells are being used in research to help treat various diseases… so

why is this controversial?

If someone has brain damage… stem cells can be grown into new brain cells to help the person recover.

Stem cell controversy• Stem cells are being used in research to help treat various diseases… so

why is this controversial?

If someone has muscle damage… stem cells can be grown into new muscle cells to help the person recover.

Stem cell controversy• Stem cells are being used in research to help treat various diseases… so

why is this controversial?

If someone is blind… stem cells can be grown into new eye cells to help the person recover.

Stem cell controversy• Stem cells are being used in research to help treat various diseases… so

why is this controversial?• Where do stem cells come from?

– When couples seek help to create a child, many eggs and sperm are collected and mixed together to create many embryos

– Embryos are implanted into the woman, where hopefully they will grow into a baby

– Stem cells are obtained from left over 4-5 day embryos• Why controversial?

– Reason: Embryo is destroyed in the process of obtaining the stem cells– Argument: Some claim this kills a human life– Counter Argument: These leftover embryos will soon be discarded as

medical waste• The Myth:

– When a woman gets an abortion, she can donate the dead embryo to stem cell research.

Determination

• Determination– Few weeks into

development– Genes program

the stem cell to become a specific cell

– Irreversible

Lump of stem cells

Differentiation

• Differentiation– Cells acquire the

structures & functions of a specialized cell

– Specific genes activated

Some stem cells become…

Differentiation

• Differentiation– Cells acquire the

structures & functions of a specialized cell

– Specific genes activated

Other stem cells become…

Differentiation

• Differentiation– Cells acquire the

structures & functions of a specialized cell

– Specific genes activated

And other stem cells become…

Quick Questions

• Do your muscle cells have the same DNA as your skin cells?

Yes

• Do your skin cells have the same DNA as your brain cells?

Yes

• Do your brain cells have the same DNA as your liver cells?

Yes

• So if all your cells have the same DNA, how do they know to do different jobs?

Stay tuned for the answer

Stem cell (soon to be muscle cell)

Stem cell (soon to be nerve cell)

If these cells have the same DNA, how will the top cell know to become a muscle cell?

Gene A Gene B Gene C Gene D Gene E Gene F Gene G

Gene A Gene B Gene C Gene D Gene E Gene F Gene G

These light switches are symbolic of the genes inside each stem cell.

Stem cell (soon to be muscle cell)

Stem cell (soon to be nerve cell)

ON ON ON

ON ON ON

During “differentiation”, certain genes are activated in some cells, but deactivated in others.

Gene A Gene B Gene C Gene D Gene E Gene F Gene G

Gene A Gene B Gene C Gene D Gene E Gene F Gene G

What do genes direct cells to create?

The proteins created in the top cell will cause the stem cell to become a muscle cell….

The proteins created in the bottom cell will cause the stem cell to become a nerve cell.

Differentiation

• Differentiation– Cells acquire the

structures & functions of a specialized cell

– Specific genes activated

Brain cells

Musclecells

Skin cells

Pancreas cells

Programmed cell death (apoptosis) between the fingers & toes

Incomplete Apoptosis(Webbed Toes)

• Cell: Basic unit

• Cell: Basic unit• Tissue: Group of cells

– 4 types

Muscle Tissue• Contracting cells• Skeletal, cardiac cells

• Cell: Basic unit• Tissue: Group of cells

– 4 types

Connective Tissue• Support the body• Bone, fat, tendons

• Cell: Basic unit• Tissue: Group of cells

– 4 types

Connective Tissue• Support the body• Bone, fat, tendons

Ligaments connect your femur (thigh bone)…

to your tibia (shin bone)

• Cell: Basic unit• Tissue: Group of cells

– 4 types

Connective Tissue• Support the body• Bone, fat, tendons

• Cell: Basic unit• Tissue: Group of cells

– 4 types

Epithelial Tissue• protective sheet of cells• skin, stomach lining

• Cell: Basic unit• Tissue: Group of cells

– 4 types

Nerve Tissue• Transmit electric signals• Brain & Spinal Cord

• Cell: Basic unit• Tissue: Group of cells

– 4 types• Organ: Groups of

tissue– Ex: lung contains

each tissue

• Cell: Basic unit• Tissue: Group of cells

– 4 types• Organ: Groups of

tissue– Ex: lung contains

each tissue• Organ System: Group

of organs working together– Respiratory System

• Cell: Basic unit• Tissue: Group of cells

– 4 types• Organ: Groups of

tissue– Ex: lung contains

each tissue• Organ System: Group

of organs working together– Respiratory System

• Cell: Basic unit• Tissue: Group of cells

– 4 types• Organ: Groups of

tissue– Ex: lung contains

each tissue• Organ System: Group

of organs working together– Respiratory System

• Cell: Basic unit• Tissue: Group of cells

– 4 types• Organ: Groups of

tissue– Ex: lung contains

each tissue• Organ System: Group

of organs working together– Respiratory System

• Organism: all organ systems working together

YouTube Review: Levels of Organization

1) What is a zygote?

2) What is the specific function of a stem cell?

3) How does “determination” differ from “differentiation”?

4) Cells are programmed to die during a process called ______.

5) From smallest to largest, name the 5 levels of organization.

6) Name the four types of tissues.

7) Which tissue is able to stretch and contract?

8) Which tissue transmits electric signals?

9) Which tissue covers and protects the body?

10) Which tissue connects the body?

Review