1. DNA: History, structure, and replication

2. Bellwork 10/3/14
1. Correct yesterday’s bellwork: carbon dioxide, light energy is converted into chemical energy.
The process of cellular respiration is essential in the oxygen/carbon dioxide cycle. Respiration removes ________ from the atmosphere and produces and releases ________ to the atmosphere.
glucose, oxygen
oxygen, glucose
carbon dioxide, oxygen
oxygen, carbon dioxide

3. DNA: What is it & why is it important?
DNA is a nucleic acid (stores genetic information). It can determine an organisms’ traits (what it looks like) by determining the structure of an organism’s proteins.

4. DNA: What is it & why is it important?
DNA is the recipe for all living things (code of life). It is found in the NUCLEUS in eukaryotic cells & free floating in the CYTOPLASM in prokaryotic cells.

5. WHO DISCOVERED DNA?
The structure of DNA was discovered through X-ray experiments by Rosalind Franklin which led James Watson and Francis Crick to the discovery of the structure of DNA in 1953
DNA is a DOUBLE HELIX
Rosalind Franklin: Great Minds

6. Figure 12–7 Structure of DNA
Section 12-1
Nucleotide
Hydrogen bonds
Sugar-phosphate backbone
Key
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)

7. DNA STRUCTURE DNA is a nucleic acid.
Nucleic acids are built up of nucleotides!
Nucleotides:
Sugar
Nitrogenous base
Phosphate
Sugar in DNA is called deoxyribose

8. DEOXYRIBONUCLEIC ACID
DNA is double stranded
Backbone (sides of ladder)
is made up of phosphates and sugars
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9. DNA STRUCTURE The rungs of the ladder are made up of nitrogen bases.
A=Adenine
G= Guanine
C = Cytosine
T= Thymine

10. Nitrogen bases =“Steps of ladder”
Purines (2 rings)
Phosphate group G C
Pyrimidines
(1 ring)
Deoxyribose sugar T
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11. A=T C=G CHARGAFF’S RULES Adenine always bonds across with THYMINE
Guanine always bonds across with CYTOSINE
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12. DOUBLE HELIX Hydrogen bonds
between nitrogen bases hold the two strands together.
Image from:

13. Antiparallel=Strands run in opposite directions
DNA IS ANTIPARALLEL
Antiparallel=Strands run in opposite directions

14. Complete the bases that will be on the other strand of DNA
TAGCTTCC
GGACTTAT
CTCAGATC

15. DNA in EUKARYOTES is packaged into chromosomes
Humans have approximately 3 billion base pairs (1 m long)
60,000 to 100,000 genes

16. DNA in EUKARYOTES is packaged into chromosomes
If the diameter of the DNA (2 nanometers) was as wide as a fishing line (0.5 millimeters) it might stretch as far as 21.2 km (or 13.6 miles) in length which would all have to be packed into a nucleus, the equivalent size of 25 cm in diameter.
That is some packaging!

17. THINK ABOUT IT
How could you get this piece of string into the container?

18. Chromosomes vs Chromatin
Unwound DNA
How DNA looks when the cell is NOT dividing
Chromosomes:
Tightly packaged DNA
Found only when the cell is dividing

19. Structure of rna RNA is the other type of nucleic acid
Made of up of many nucleotides
Three main differences from DNA:
Sugar is ribose
Single stranded
Replace Thymine with Uracil
RNA can leave the nucleus & DNA can not!! *this is really important when we get to protein synthesis 

20. RNA VS DNA

22. How is dna copied?
DNA is copied through a process called DNA replication.
It takes place in the NUCLEUS of a cell!
It occurs in the S phase of the cell cycle.

23. How is dna copied? Semiconservative Replication=
the DNA molecule breaks down the middle and each half is the pattern to make a new half!

24. DNA REPLICATION STEPS
An enzyme called helicase unzips DNA – hydrogen bonds are broken.
Now there are two separate strands of DNA!!

25. DNA REPLICATION STEPS
2. DNA Polymerase adds matching bases to one side of the DNA strand (A+T, G+C)
DNA Polymerase

26. DNA REPLICATION STEPS
3. DNA Polymerase checks the new strands to make sure they are matched correctly.
4. Ligase comes in & glues the DNA back together.

27. DNA REPLICATION STEPS
5. Two identical strands of DNA now exist!

28. DNA Replication: The Cell’s Extreme Team Sport
DNA REPLICATION VIDEO
DNA Replication: The Cell’s Extreme Team Sport

29. Figure 16.7 A model for DNA replication: the basic concept (Layer 1)

30. Figure 16.7 A model for DNA replication: the basic concept (Layer 2)

31. Figure 16.7 A model for DNA replication: the basic concept (Layer 3)

32. Figure 16.7 A model for DNA replication: the basic concept (Layer 4)

33. Replication: http://www. youtube. com/watch
Replication: Real Time:

34. DNA Replication Song