Regents Biology Biology is the only subject in which multiplication is the same thing as division…

Regents Biology Where it all began… You started as a cell smaller than a period at the end of a sentence…

Regents Biology And now look at you… How did you get from there to here?

Regents Biology  Going from egg to baby…. the original fertilized egg has to divide… and divide… Getting from there to here…

Regents Biology Why do cells divide…  One-celled organisms  for reproduction  asexual reproduction (clones)  Multi-celled organisms  for growth & development  from fertilized egg to adult  for repair & replacement  replace cells that die from normal wear & tear or from injury amoeba starfish

Regents Biology Dividing cells…  What has to be copied  DNA  organelles  cell membrane  lots of other molecules  enzymes animal cellplant cell

Regents Biology Copying DNA  A dividing cell duplicates its DNA  creates 2 copies of all DNA  separates the 2 copies to opposite ends of the cell  splits into 2 daughter cells  But the DNA starts loosely wound in the nucleus  If you tried to divide it like that, it could tangle & break nucleus cell DNA

Regents Biology Organizing & packaging DNA nucleus cell DNA nucleus cell 4 chromosomes in this organism DNA in chromosomes in everyday “working” cell DNA in chromosomes in cell getting ready to divide DNA has been “wound up”

Regents Biology Chromosomes of Human Female 46 chromosomes 23 pairs

Regents Biology Chromosomes of Human Male 46 chromosomes 23 pairs

Regents Biology Copied & Paired Up Chromosomes centromere

Regents Biology double-stranded human chromosomes ready for mitosis

Regents Biology DNA must be duplicated… nucleus cell DNA in chromosomes nucleus cell duplicated chromosomes chromosomes in cell 4 single-stranded chromosomes duplicated chromosomes 4 double-stranded chromosomes

Regents Biology  MITOSIS  The nucleus divides into two  CYTOKINESIS  The cell divides in two

Regents Biology New “daughter” cells  Get 2 exact copies of original cells  same DNA  “clones”

Regents Biology Mitosis in whitefish embryo

Regents Biology onion root tip

Regents Biology Remember where it all began… You started as a cell smaller than a period at the end of a sentence… How did that become you? Billions and billions of cells that are all of a specific type… You have lots of cells that are each of a different type. They become that different type through a process called differentiation.

Regents Biology Let’s connect the menu activity to differentiation. Creating a menu  Each of you had 11 cookbooks to work with.  You chose the recipe that was necessary for your particular event.  The food will be prepared.  Your party becomes a specific type of party!  Once the party starts, you can’t change the theme in the middle. Inside the cell  Every cell has 23 pieces of DNA to work with.  Only the genes necessary for a particular cell will be “turned on” or expressed.  Those particular proteins will be synthesized by the cell.  The cell becomes a specialized type of cell!  Once the cell differentiates, it can’t develop into a different kind of cell.

Regents Biology Remember where it all began… You started as a cell smaller than a period at the end of a sentence… What process makes this happen? These cells will become all types of cells in the embryo Since all cells in the embryo stem from these cells, we call these… AD: Since these cells have the potential to become all types of cells they are totipotent.

Regents Biology Stem cells can also be adult.  One example are stem cells in your bone marrow that can become all kinds of blood cells. AD: Since these cells have the potential to become multiple types of cells, but not all, they are pluripotent.

Regents Biology How are stem cells like the stem of a plant?

Regents Biology What do you remember?  Humans, pets, and petunias all pass through an early stage of development called a(n) ………  Embryo

Regents Biology What do you remember?  Cells become ………….. through the process of differentiation.  Specialized

Regents Biology What do you remember?  Most cells in the adult human body are no longer capable of ………………..  Differentiating

Regents Biology What do you remember?  Which is an example of a totipotent cell? A. Blastocyst B. Bone cell C. Fertilized egg D. Lymphocyte

Regents Biology What do you remember?  Adult stem cells are best described as A. Multipotent B. Pluripotent C. Totipotent D. Unable to differentiate