Cell Signaling and Cloning. How do cells differentiate? Determination 1. When a cell “chooses” a particular fate. 2. Happens via cell signaling or asymmetrical.

Cell Signaling and Cloning

How do cells differentiate?

Determination1. When a cell “chooses” a particular fate.

2. Happens via cell signaling or asymmetrical cell division.

Differentiation (when the cells actually begin to change/become different from one another)

1. Caused by differential gene expression due to inductive signals

2. Results in changes in cell function, shape (morphology), location

A cell first becomes “determined” via induction, later it differentiates via induction

Example of induction, determination, and differentiation at work!

The pressing question… meiosis or mitosis?

Meiosis or Mitosis?

How do we go from gametes to a “full-fledged” organism?Fertilization (egg + sperm meet) = zygote.Many rounds of cell division (we do need more than one

cell to perform all our many functions, after all!). This cell division is called MITOSIS.

Cells become specialized.

Meiosis or Mitosis?



Cells become specialized.

Meiosis or Mitosis?



Cells become specialized.• Note: Up through the

BLASTULA stage in humans, cells are UNDIFFERENTIATED

Write this down!!!

How do “sex cells” become “sex cells?”

A germ cell is a cell that gives rise to sex cells. The very first germ cells are called “primordial germ cells” and are initially located outside of the sex organs. (Primordial means “original” or “the first”).

Primordial germ cells

Migrate to sex organs. Divide while migrating.

(diploid)

(diploid)Germ cells

Meiosis

Gametes(haploid)


Primordial germ cells originate near the cells in the developing embryo that eventually become the gut.

Endoderm (gut) *Note: this is a cell in the “gastrula” phase


What determines which cells become primordial germ cells in the early embryo?

1. Asymmetrical cell division (in animals other than mammals and birds)

2. Induction by neighboring cells (in mammals and birds)

*Note: this is a cell in the “gastrula” phase


= “sex cell molecule”

1. Asymmetric cell division


1. Induction by neighboring cells


1. Induction by neighboring cellsHey, you guys. Become a sex cell!


In order for a sex cell (or any cell) to become a specialized cell…1. That cell must become determined. This happens via asymmetrical division or

inductive signals from other cells.

2. Sometime later, the cell receive an inductive signal that tells it to begin to differentiate.

*Note: this is a cell in the “gastrula” phase

An example of induction relating to body part differentiation

Meiosis or Mitosis?



Cells become specialized.• Note: Up through the

BLASTULA stage in humans, cells are UNDIFFERENTIATED

Write this down!!!


= “sex cell molecule”

1. Asymmetric cell division

Asymmetric Division

Cytoplasmic determinants: substances in the maternal gamete (egg) that affect the course of early development by regulating gene expression, which in turn affects cell fate.

Cell fate: what a cell eventually becomes. When a cell is said to be “determined,” its cell fate is decided.

Differential gene expression is NOT due to loss of genetic informaiton

All of the somatic cells in an organism contain the same DNA

Different types of cells express different genes. This is what makes cells different from one another.

All somatic cell nuclei contain all the information needed to construct an entire organism.

How can we prove that cells do not lose genetic information as they differentiate?

Cloning!

How can we prove that cells do not lose genetic information as they differentiate?

CloningClone: An exact genetic copy of an organism.

• Natural clones? Identical twins!

Cloning Steps

Cell Signaling and Cloning. How do cells differentiate? Determination 1. When a cell “chooses” a particular fate. 2. Happens via cell signaling or asymmetrical.

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