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Transcript
Biology is the only subject in which multiplication is the same thing as division… Regents Biology 2006-2007 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… Regents Biology How did you get from there to here? Getting from there to here… Going from egg to baby…. the original fertilized egg has to divide… and divide… and divide… and divide… Regents Biology Why do cells divide… One-celled organisms for reproduction asexual reproduction (clones) amoeba 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 Regents Biology starfish Dividing cells… What has to be copied DNA organelles cell membrane lots of other molecules enzymes Regents Biology plant cell animal cell 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 DNA cell Regents Biology nucleus But the DNA starts loosely wound in the nucleus If you tried to divide it like that, it could tangle & break Organizing & packaging DNA DNA cell nucleus DNA has been “wound up” DNA in chromosomes in everyday “working” cell cell nucleus 4 chromosomes in thisBiology organism Regents DNA in chromosomes in cell getting ready to divide 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… chromosomes in cell DNA in chromosomes cell nucleus 4 single-stranded chromosomes duplicated chromosomes duplicated chromosomes Biology chromosomes 4Regents double-stranded cell nucleus MITOSIS The nucleus divides into two CYTOKINESIS Regents Biology The cell divides in two 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. Regents Biology 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. Remember where it all began… You started as a cell smaller than a period at the end of a sentence… AD: Since these cells have the potential to become all types of cells they are totipotent. Since all cells in the embryo stem from these cells, we call these… 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 Regents Biology