Teacher Notes  This PPT was revised November 19,  This PPT is a companion PPT to Mitosis & Meiosis.  There is a handout for this PPT.

Reproduction & DNA Replication How does DNA copy itself?

Why do cells divide?  to increase surface area  to repair damaged cells  to produce sex cells  to grow

Cell Reproduction Cells reproduce either sexually or asexually. Bacteria

 Requires only one parent  Binary Fission  Budding  Vegetative Propagation  Regeneration Asexual Reproduction

Advantages of Asexual Reproduction  offspring cells are exactly like the parent cell (clones) Speed Desirable Characteristics Replacement

TRY THIS!  On your notebook paper draw a Verbal Visual table for Asexual Reproduction Vocabulary TermDefinition DrawingNon-Example

TRY THIS! Vocabulary Term Asexual Reproduction Definition Requires only one parent DrawingNon-example sperm and egg

Sexual Reproduction  Sexual reproduction requires two parents.  Two sex cells (called gametes) must unite. Fertilized Egg Cell

Fertilization  Fertilization is the union of egg & sperm. New Individual 46 Mom 23 Dad 23

Advantages of Sexual Reproduction  Offspring are unlike the parent.  Sexual reproduction provides diversity in a species.

ant 2 chromosomes Chromosome Number  Every species has a specific number of chromosomes that every body cell is supposed to have. crayfish 200 chromosomes human 46 chromosomes dog 78 chromosomes

Chromosome Number  Since you inherit half of your chromosomes from each parent, you carry two complete sets of chromosomes. mother crayfish 100 chromosomes father crayfish 100 chromosomes 1 set of sets = 200 crayfish 200 chromosomes

Homologous Chromosomes homologous  These two complete sets of chromosomes are homologous, the chromosomes from the female parent have a corresponding chromosome from the male parent. mother crayfish 100 chromosomes father crayfish 100 chromosomes 1 set of sets = 200 crayfish 200 chromosomes

Homologous Chromosomes  Homologous chromosomes are similar in size and shape and control the same traits. from

Chromosome Number  Humans inherit one set of 23 chromosomes in the egg from the mother and one set of 23 on the sperm from the father.  This gives the child 2 homologous sets of chromosomes

Chromosome Number  The single set of one chromosome of each type inherited from one parent is called haploid.  Haploid: 1 set of chromosomes (n) found in gametes (egg or sperm) 23 Chromosomes

Chromosome Number  A cell (such as a fertilized egg) with two sets of homologous chromosomes is called diploid.  Diploid: 2 sets of chromosomes (2n) found in body cells (somatic) 46 chromosomes

Chromosome Number Recall that every body cell in an organism must have the specific 2n chromosome number for that species.  If body cells do not have the correct 2n chromosome number, the cell will not _?_. humans must have 46 chromosomes  Why is it important for every body cell in an organism to have the specific 2n chromosome number for that species?.

How does this happen?  When we grow by our cells dividing to make two new cells, all of those new cells must have 46 chromosomes.  How do we get 92 chromosomes (46 for each new cell) from a cell with only 46 chromosomes? 46

Chromosome Number  The doubling of the chromosomes is actually DNA making an exact copy of itself. This is called DNA replication. 46 Then each new cell can receive the correct number of chromosomes (DNA). 4692

 Create a Venn diagram for asexual and sexual reproduction. TRY THIS!

A Cell’s Life Cycle  When does a cell divide?  Most of a cell’s life cycle is spent in Interphase when it performs normal life functions.  Green section M G1G1 S G2G2 G1G1 C

A Cell’s Life Cycle  When does a cell divide? Only a small part of the cell cycle is spent in division. The RED section marked letter M M G1G1 S G2G2 G1G1 C

A Cell’s Life Cycle  When does DNA replication occur? Interphase  During Interphase, (in the S/Synthesis phase), the DNA replicates (makes a copy of itself). M G1G1 S G2G2 G1G1 C

DNA Replication  Before a cell divides the DNA must replicate (make an exact copy of itself) so the new cells have the right 2n # of chromosomes.

DNA Replication  Each new cell must have the same chromosome number (and same DNA) as the parent cell to function properly.

DNA Replication  Replication occurs in 3 easy steps…

DNA Replication 1. DNA Unzips  An enzyme unzips the molecule by breaking the hydrogen bonds that hold the nitrogen bases together.

DNA Replication: 1. DNA Unzips 3’End 5’End A T T C C G Left 5’ Strand of Original DNARight 3’ Strand of Original DNA 3’End 5’End A T A G G C 5” End

2. Bases Pair  Complementary bases match with each base in the original DNA strand  What is the complementary base pairing rule?  A = T  G  C

DNA Base Pairing – Step 2 3’End 5’End A T AG G C 3’End 5’End A T T C C G T C A GG C A T G T A C

3. Two Identical DNA molecules  Two new DNA molecules each have the same DNA nitrogen base sequence.  The new DNA molecules are exactly like the original. T C C A G G T C C A G G T C C A G G

DNA Replication Review  Explain what is happening at each step in DNA Replication. Step 1 Step 2 Step 3

 What molecule is at I? DNA Replication Review  What process is occurring?  What is happening at II (the arrow)?  What are the structures at III (circle)?I II V V III IV

 What are the two molecules at V? DNA Replication Review  What is happening at IV??  How many strands are formed? I II V V III IV  What are the new strands like compared to the original?  What are the new strands like compared to each other?

MITOSIS  Now that DNA has replicated and the cell now has two identical sets of DNA/ chromosomes  cell division (mitosis/meiosis) can begin T C C A G G T C C A G G

MITOSIS  What is the purpose of DNA replication?  (Hint: think of the importance to the cells produced) T C C A G G T C C A G G 46 92

TRY THIS!  On your paper create a 3 Column Self- Assessment Chart for Cell Reproduction and DNA Replication What I Know… What I Don’t Know… What I Wish I Knew…

Works Cited  There is a nice animation of DNA Replication at  DNA Replication diagram, artist Darryl Leja, National Human Genome Research Institute (NHGRI)  Background DNA Replicaiton image, DOE Human Genome project, Department of Energy, (  DNA Replication diagram, artist Darryl Leja, National Human Genome Research Institute (NHGRI)  “Fertilization - sperm fertilizing egg”, (No Date). Wikipedia.com, Retrieved June 20, 2006 from the World Wide Web: Website Copyright Permission: This image is copyrighted. However, the copyright holder has irrevocably released all rights to it, allowing it to be freely reproduced, distributed, transmitted, used, modified, built upon, or otherwise exploited in any way by anyone for any purpose, commercial or non-commercial, with or without attribution of the author, as if in the public domain.copyrighted