1. Draw & Label the stages of mitosis (New BW page)
Monday February 5
Draw & Label the stages of mitosis (New BW page)

2. ClassWork – When finished with your test corrections
Review pages
Read pages
Answer questions p. 202 #1-8
Questions page 210 #1-2
Questions page , 25

3. 2/6/18 Science “DYRT” Quiz You need a half sheet of paper
Be looking over pages

4. Amoeba Sisters Video

5. DNA Replication the big event during S phase

6. Chromosomes are made of DNA. Genes are sections of DNA.
DNA Structure Review
James Watson and Francis Crick (& Rosalind Franklin) discovered the structure of DNA
Chromosomes are made of DNA. Genes are sections of DNA.
DNA controls the production of proteins that determine traits.

7. DNA Structure Review Twisted ladder/double helix
DNA is made of components called “nucleotides”.
A nucleotide includes a base, a sugar, and a phosphate

8. DNA Structure Review
The sides of the ladder are made up sugar and phosphate groups
The rungs are made up of nitrogen bases (2)
The bases are connected to the sugar

9. 4 Nitrogen Bases A only pairs with T C only pairs with G
1) Adenine (A)
2) Guanine (G)
3) Cytosine (C)
4) Thymine (T)
A only pairs with T
C only pairs with G
1) Adenine (A)
2) Guanine (G)
3) Cytosine (C)
4) Thymine (T)
A only pairs with T
C only pairs with G

10. DNA Replication Overview
A) required prior to cell division for both mitosis and meiosis (Formation of sex cells)
B) Occurs in both prokaryotes & eukaryotes
C) Occurs during the S (synthesis) stage of interphase in cell cycle. Cells replicate DNA before cell division.
D) Takes place in nuclei of eukaryotes

11. KEY Players 1. Helicase- Unzipping enzyme (unzips two strands)
All Enzymes speed up reactions by building up or breaking down items they act on
1. Helicase- Unzipping enzyme (unzips two strands)
2. DNA Polymerase-Builder- this enzyme replicates DNA molecules to build new strand
3. Primase- Initializer – DNA cant figure out where to get started without primer. Primase makes the primer so that polymerase knows where to go to the start the work. Primer is made of RNA.
4. Ligase-GLUER- glues DNA fragments together.

12. Creates replication bubbles
Replication starts at the ORIGIN OF REPLICATION (a specific nucleotide sequence)
Creates replication bubbles

13. In prokaryotic cells there is one origin
In eukaryotic cells there are 100’s to 1000’s of origins

14. DNA is semi-conservative
This means that one half of the DNA strand is being used to make the other half.
This also means that one strand of the DNA is an original and the other half is brand new.

15. DNA Replication is semi-conservative:
each replicated DNA molecule consists of one “old” and on “new” strand.

16. Step One The DNA molecule unwinds
Helicase breaks the hydrogen bonds between the two strands.
Is an enzyme made during G1
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17. Step Two
Single stranded binding proteins (SSBs) hold the two strands of DNA apart
This adds stability.

18. Step Three
RNA Primase makes short sections of RNA nucleotides that bind with complementary base sequences
These RNA nucleotides act as a primer for DNA nucleotides.
Primers are short segments of RNA, about 10 nucleotides long
Must have a primer because DNA polymerase can only add nucleotides to another nucleotide
Primase

19. Step Four
DNA polymerase III adds DNA nucleotides to the RNA primer sequence in a 5’ to 3’ direction. New nucleotides can only be added to the 3’ end of a growing DNA chain So we say DNA elongates in a 5’ to 3’direction

20. Step Four Leading Strand:
DNA polymerase III can synthesize a complementary strand on one side of the template in the 5’ to 3’ direction with no problem.

21. What about the other strand??5’ 3’
DNA Polymerase III
Can only add to this side …
AWAY from the
replication fork

22. Lagging Strand
DNA polymerase III must work away from the replication fork.
Makes a short strand of DNA, called an Okazaki fragment.
As the bubble widens, it can make another short strand, and so on.

23. Step Four Lagging Strand
DNA polymerase III must work away from the replication fork.
Makes a short strand of DNA, called an Okazaki fragment.
As the bubble widens, it can make another short strand, and so on.

25. Step Five
RNA primers are removed and replaced with DNA nucleotides by DNA Polymerase I.

26. Step Six
Along the lagging strand the Okazaki fragments are joined by DNA Ligase to form a single DNA strand.

27. Step Seven
Throughout the process proofreading is done by DNA Polymerase III and I and again, until replication is complete.

28. Know them well

29. Accurate Only 1:1,000,000,000 nucleotides are incorrectly paired
DNA replication is ...
Accurate
Only 1:1,000,000,000 nucleotides are incorrectly paired

30. DNA replication is ... Extremely rapid
In prokaryotes, up to 500 nucleotides are added per second
50 per second in eukaryotes

31. Other Good Animations Interactive website
Review video