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

Regents Biology MITOSIS: Making New Cells Making New DNA

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

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 Paired bases  DNA structure  double helix  2 sides like a ladder  Bases match together  A pairs with T  A : T  C pairs with G  C : G phosphate sugarN base

Regents Biology Watson and Crick

Regents Biology Copying DNA  Matching bases allows DNA to be easily copied

Regents Biology Making new DNA  Copying DNA  replication  DNA starts as a double-stranded molecule  matching bases (A:T, C:G)  then it unzips…

Regents Biology DNA replication  Strands “unzip” at the weak bonds between bases

Regents Biology DNA replication DNA polymerase  Enzyme  DNA polymerase  adds new bases DNA bases in nucleus

Regents Biology DNA Polymerase Copying DNA  Build daughter DNA strand  use original parent strand as “template”  add new matching bases  synthesis enzyme = DNA polymerase

Regents Biology New copies of DNA  Get 2 exact copies of DNA to split between new cells DNA polymerase DNA polymerase

Regents Biology Copied & Paired Up Chromosomes centromere

Regents Biology Copying & packaging DNA Copying DNA Coil DNA into compact chromosomes  When cell is ready to divide…  copy DNA first, then…  coil up doubled chromosomes like thread on a spool…  now can move DNA around cell without having it tangle & break

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: Dividing DNA & cells  Stage 1: cell copies DNA nucleus cell DNA Copy DNA! (interphase)

Regents Biology Mitosis: Dividing DNA & cells  Stage 2: DNA winds into chromosomes  DNA is wound up into chromosomes to keep it organized nucleus cell duplicated chromosomes Wind up! (prophase)

Regents Biology Mitosis: Dividing DNA & cells  Stage 3: Chromosomes line up  chromosomes line up in middle  attached to protein “cables” that will help them move duplicated chromosomes lined up in middle of cell Line up! (metaphase)

Regents Biology Mitosis: Dividing DNA & cells  Stage 4: Chromosomes separate  chromosomes split, separating pairs  start moving to opposite ends chromosomes split & move to opposite ends Separate! (anaphase)

Regents Biology Mitosis: Dividing DNA & cells  Stage 5: Cell starts to divide  cells start to divide  nucleus forms again Divide! (telophase)

Regents Biology Mitosis: Dividing DNA & cells  Stage 6: DNA unwinds again  cells separate  now they can do their every day jobs Bye Bye! (cytokinesis)

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

Regents Biology Cell division in Animals

Regents Biology Mitosis in whitefish embryo

Regents Biology Mitosis in plant cell

Regents Biology onion root tip

Regents Biology Overview of mitosis interphaseprophase metaphaseanaphasetelophase cytokinesis I.P.M.A.T.C. P lease M ake A nother T wo C ells