Monday, March 19, 2012 If you were absent on Friday, you need to makeup the checkup… in tutorial TODAY. Homework: None

Make an entry- Entry 23: Mitosis- 3/19/12

Answer the following questions: 1.Why would a cell need to copy its DNA? 2.DNA is in the nucleus and doesn’t leave it. If both new cells need DNA how could this problem be solved? 3.Once DNA is copied, how could you make sure that exactly half goes in one cell and exactly half in the other cell? 4.If a cell divides into two cells, why don’t cells get smaller and smaller with each division? 5.How could two new cells be made from one original cell?

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

Regents Biology 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 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…  For growth & development  from fertilized egg to multi-celled organism  For repair  replace cells that die from normal wear & tear or from injury  for reproduction  Transmit genetic information to later generations (meiosis) We will study this later. amoeba

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

nucleus chromosome

In the cell, DNA forms structures called chromosomes A eukaryotic chromosome is typically a very long, single chain of DNA

Chromosomes of Human Female 46 chromosomes 23 pairs

Chromosomes of Human Male 46 chromosomes 23 pairs

chromosome A gene is a region of the chromosome which contains information for making a protein gene A chromosome has thousands of genes

Mitosis Produces two identical daughter cells Each daughter cell has the same kind and number of chromosomes as the original parent cell Mitosis takes place after DNA replication.

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 double-stranded human chromosomes ready for mitosis

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 (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 Copy DNAWind Up Line UpSeparateDivide

Regents Biology Any Questions??

Can you identify the different stages of mitosis from the diagram below? metaphase anaphase prophase interphase telophase

ABNORMAL CELL DIVISION Sometimes cells cannot stop dividing and they go through uncontrolled cell division becoming cancerous cells or tumors. Uncontrolled cell division in white blood cells causes leukemia. Skin cancer

DNA checkups returned 11/15 or less to raise to 12/15