1. Key Concepts What events take place during the three stages of the cell cycle? How does the structure of DNA help account for the way in which DNA copies itself?

2.  Cell cycle  Interphase  Replication  Mitosis  Chromosome  cytokinesis

3.  Cell Cycle – the regular sequence of growth and division that cells undergo ◦ Cells grow, divide into 2 cells called daughter cells  Interphase is the period before cell division where the cell grows, makes a copy of its DNA, and prepares to divide into 2 cells

4. Growing – during first part grows to full size and produces structures it needs. – Makes copies of both mitochondria and chloroplasts Copying DNA – makes exact copy of DNA in a process called replication (each daughter cell must have a complete set of DNA Preparing for division- cell produces structures it will use to divide into 2 cells

5.  The stage during which the cell’s nucleus divides into 2 new nuclei  One copy of the DNA is distributed to each daughter cell  Mitosis has 4 parts or phases: ◦ Prophase ◦ Metaphase ◦ Anaphase ◦ Telophase

6.  Chromatin condenses to form chromosomes  Chromosomes are double-rod structures. They are double because the DNA in the cell has replicated ( made a copy of itself)  Each identical rod is called a chromatid  The two chromatids are  held together by  a centromere

7.  Chromosomes line up across the center of the cell.  Each chromosome attaches to a spindle fiber at centromere

8.  Centromeres split. 2 chromatids separate and are drawn by spindle fibers to opposite sides of the cell  The cell stretches out

9.  Chromosomes stretch out. Lose rod-like appearance  New nuclear envelope forms around each region of chromosomes

10.  Final stage of cell cycle  The cytoplasm divides. The organelles are distributed into each of the 2 new cells  Starts at same time as telophase  Ends and the cell goes into interphase  In animals, cell membrane pinches in  In plants, a cell plate forms across the middle of the cell. Gradually develops into new cell membranes. Then new cell walls form around the membrane

11.  Structure was discovered through the work of 3 scientists:  Rosalind Franklin – used an x-ray method to photograph DNA molecules in 1952  James Watson and Francis Crick – used photographs to create a 3-D model showing the helical (spiral) structure of DNA in 1953

12.  Looks like a twisted ladder or spiral staircase  Sides are made of a sugar – deoxyribose alternating with a phosphate  Rungs are pairs of molecules called nitrogen bases. 4 types: adenine (A), thymine (T), guanine (G), and cytosine (C)  Adenine only pairs with thymine  Guanine only pairs with cytosine

13.  2 sides of DNA molecule unwind and separate  Nitrogen bases that are floating in nucleus pair up with bases on either side.  Because of the way in which N bases pair with one another, the order of bases in the new strands of DNA are exactly the same as the original strand  Ends with 2 strands of DNA

14.  http://botit.botany.wisc.edu/images/130/meiosi s/lilium_microsporogenesis/interphase.html http://botit.botany.wisc.edu/images/130/meiosi s/lilium_microsporogenesis/interphase.html  http://members.chello.nl/r.kuijt/en_mitosis.htm http://members.chello.nl/r.kuijt/en_mitosis.htm  http://allstrangledup.wordpress.com/ http://allstrangledup.wordpress.com/  http://student.ccbcmd.edu/~gkaiser/biotutorials /dna/mitosis/pcinterphase.html http://student.ccbcmd.edu/~gkaiser/biotutorials /dna/mitosis/pcinterphase.html  http://imcurious.wikispaces.com/Midterm+Exam +2010+Review+P2 http://www.cas.unt.edu/~tpp001/Mitosis_Diagra m_Page.main.html http://imcurious.wikispaces.com/Midterm+Exam +2010+Review+P2 http://www.cas.unt.edu/~tpp001/Mitosis_Diagra m_Page.main.html  http://www.dna-sequencing-service.com/dna- sequencing/dna-structure/ http://www.dna-sequencing-service.com/dna- sequencing/dna-structure/

15.  http://www.achievement.org/autodoc/photoc redit/achievers/wat0-032 http://www.achievement.org/autodoc/photoc redit/achievers/wat0-032  http://sciencecomm.wikispaces.com/UNIT+2 _Did+Rosalind+Franklin+deserve+the+Noble +Prize%3F http://sciencecomm.wikispaces.com/UNIT+2 _Did+Rosalind+Franklin+deserve+the+Noble +Prize%3F  http://www.packer34.freeserve.co.uk/remem beringfranciscrickacelebration.htm http://www.packer34.freeserve.co.uk/remem beringfranciscrickacelebration.htm  http://library.thinkquest.org/C006188/basic s/replication.htm http://library.thinkquest.org/C006188/basic s/replication.htm