1. Transcription and Translation
DNA Replication
Transcription and Translation

2. Genes are Made of DNA
Scientist discovered that DNA was a chemical inside the nucleus
Oswald Avery
1944
Frederick Griffith 1928

3. Genes are Made of DNA Further experiments by: Alfred Hershey
Martha Chase
Worked with viruses to support Avery’s work

4. Genes are Made of DNA
Virus – a package of nucleic acid wrapped in protein
Not made of cells
They can only reproduce by infecting a living cell
Bacteriophage – a virus that infects bacteria

5. The Double Helix Double Helix – Model created by Watson and
At more or less the same time scientist:
James Watson
Francis Crick
Using Franklin’s X-ray crystalography to provide clues to their discovery
Double Helix – Model created by Watson and
Crick; in which two strands of
nucleotides wound about each
other
Sugar phosphate backbones on the outside; Nitrogenous base on the inside.

6. Remember the monomer of DNA is a nucleotide

7. What is DNA and RNA??
DNA and RNA are a class of macromolecules called Nucleic Acids
DNA (Deoxyribonucleic Acid)
where genetic information is stored
Composed of
Deoxyribose sugar
Phosphate group
Nucleotide base
Double stranded
RNA (Ribonucleic Acid)- involved in protein synthesis
Composed of the sugar ribose, a phosphate group, and nitrogenous base
Has the nitrogen base uracil in place of thiamine

8. DNA - Nucleotides
Each DNA and RNA monomer has three parts:

9. DNA - Nucleotides Nitrogenous Base – 4 nucleotides found in DNA
differ only in their nitrogenous
bases
Pyrimidines: single ring structure
Thymine (T)
Cytosine (C)
Purines: double ring structure
Adenine (A)
Guanine (G)

10. DNA structure and bonding
DNA is composed of
the sugar-phosphate “backbone”
The nitrogenous bases “rungs”
The sugar-phosphate molecules are joined by covalent bonds
The nitrogen bases are joined by hydrogen bonds

11. Complementary Base Pairs
Pyrimidines always pair with purines
Base Pairing Rules
A with T
C with G
AT CG (Coral Gables)

12. Chargaff’s rule If…. Adenine (A) only pairs with Thiamine (T)
Guanine (G) only pairs with Cytosine (C)
Then for every DNA molecule,
the amount of A=T
The amount of C=G
C% + G% = 100%- (A% + T%)

13. Practice Problem A molecule of DNA is composed of 20% Adenine.
What % is Thiamine?
What % is Guanine?
What percent is Cytosine?

14. A= 20% A=T; T=20% A+T= 40% (C% + G%) = 100% - 40%= 60% C = G, then

15. You Practice
Given the following problems, figure out the % of the rest of the nucleotides
10 % guanine
15% thiamine
30% cytosine

16. You Do: Draw a DNA Molecule
Draw a molecule of DNA
Make sure to color code
Phosphate Group
Deoxyribose sugar
Nitrogenous Bases
Adenine
Guanine
Thymine
Cytosine
Show which bonds are hydrogen bonds and which are covalent bonds

17. DNA Replication
When a cell divides; a complete set of genetic instructions are copied for each cell
Genetic material uses the template principle to make more DNA
Watson and Crick’s model for DNA allowed for the hypothesis of specific base pairing
A – T
C - G
If you know one strand of DNA you can determine the sequence on the other

18. What is the essential vocabulary?
Replication – the process of DNA duplication.
Replication fork – Site where DNA strands separate and replication occurs.
Enzyme – a protein that facilitates a specific chemical reaction in the body.
Leading strand – DNA strand that forms as a continuous strand during DNA replication.
Lagging strand – DNA strand that forms as a series of short segments, called Okazaki fragments, which are then connected together.

19. What is DNA replication?
During DNA replication, the DNA molecule produces two new complementary strands.
Each strand of DNA serves as a template for the new strand.
Described as semiconservative because each DNA molecule has one new strand and one original strand.
New nucleotides are always added in the 3’ to 5’ direction

21. How does DNA replication work?
A very complex process requiring the assistance of several enzymes and regulatory molecules.
DNA helicases unwind parent strand.
Primase initiates replication by adding a short RNA fragment called a primer to the old strands
DNA polymerases join individual nucleotides to produce a new strand of DNA using the old strand as a template. They also carry out DNA proofreading and repair.
Ligase binds the DNA fragments together by addition of phosphates in the gaps that remain in the phosphate-ribose sugar backbone.
These enzymes are the crucial parts of replication assembly line. The precision with which every single segment of the complementary strand is aligned is mind-boggling. No man-made assembly line can match the efficiency, detailing and brilliance of the DNA replication mechanism that makes biological inheritance possible.
Helicase DNA replication begins at places called origins, within the DNA molecule and the creation of replication forks. The process of strand separation is made possible because of the enzyme Helicase which separates the two strands using the energy that is derived from ATP hydrolysis. DNA Primase One of the most crucial enzymes is DNA Primase. After the DNA strands are separated, to begin the creation of new DNA molecules, through addition of complementary bases to the templates, a short RNA segment, called a 'primer' is required. These primers are synthesized by DNA primase enzymes, thus initiating the DNA replication process. That is why DNA Primase is one of the most important DNA replication enzyme. DNA Polymerase The most important enzymes, that carry out the main task of aligning the complementary bases with template strands of 'unzipped' DNA, are the DNA polymerases. They are a large family of enzymes that carry out the task of adding complementary base nucleotides by reading the template strands. Besides the task of elongating the DNA molecule, they also carry out DNA proofreading and repair. DNA Ligase While Helicase works to unwind the DNA molecule, DNA Ligase is the DNA replication enzyme that binds the DNA fragments together by addition of phosphates in the gaps that remain in the phophate-ribose sugar backbone.

22. DNA Replication Overview
Each strand of the DNA double helix has all the information needed to reconstruct the other half by the mechanism of base pairing.
Because each strand can be used to make the other strand, they are said to be complementary. A T C G T A A T G C
(a) Parent molecule

23. DNA Replication Overview
DNA helicase begins replication by separating the strands and exposing the nucleotide sequence.
Primase adds a primer to the DNA molecule to initiate replication
DNA polimerases move along the two strands, pairing complementary bases to the exposed nucleotides and proofreads the added segments A T A T C G C G T A T A A T A T G C G C
(a) Parent molecule
(b)
Separation of strands

24. DNA Replication OverviewG C G C G C G T A T A T A T A A T A T A T A T G C G C G C G C
(a) Parent molecule
(b)
Separation of strands
(c)
“Daughter” DNA molecules, each consisting of one parental strand and one new strand
DNA ligase seals up the fragments into one long continuous strand
Each original strand joins its complementary strand to form a DNA molecule, resulting in two identical DNA molecules.

25. DNA Replication Overview