1. DNA and RNA
– DNA image

2. They all share a universal genetic code.
What do all of these organisms have in common?
The answer – Universal genetic code
They all share a universal genetic code.

3. How do we know that all of our genetic information comes from DNA?
Thanks to many scientists and many experiments over the last ≈ 90 years.
Let’s take a look…….

4. Who helped?
In 1928: Griffith accidentally discovered a process called Transformation that turned non-deadly bacteria into deadly pneumonia causing bacteria.
In 1944: Avery, McCarty, and MacLeod Repeated Griffith’s Experiment
Discovered DNA was the transformation factor.
In 1952: Hershey-Chase experimented with bacteria and bacteriophages. Showed DNA was what entered the bacteria and caused disease.

5. DNA carries the genetic code!
Now we know!
DNA carries the genetic code!
But, how do we know how it works?

6. DNA’s Structure was the key!
How did DNA:
1. Store information?
2. Duplicate itself easily?
DNA’s Structure was the key!

7. The Race to Discover DNA’s Structure
Why do you think the bases match up this way?
1950
Chargaff’s Rule: Equal amounts of Adenine and Thymine, and equal amounts of Guanine and Cytosine
Purine + Purine = Too wide
Pyrimidine + Pyrimidine = Too Narrow
Erwin Chargaff
Purine + Pyrimidine = Perfect Fit from X-ray data

8. The Race to Discover DNA’s Structure
X-Ray diffraction image of DNA taken by Franklin in 1951
Maurice Wilkins
Rosalind Franklin

9. The Race to Discover DNA’s Structure
1953
Compiled data from previous scientists to build a double-helical model of DNA
James Watson
Francis Crick

10. DNA and RNA are Nucleic Acids
What is a nucleic acid?
Nucleic acids are one of the major organic biomolecules.

11. Nucleic Acids They contain C, H, N, O, P
They are made of nucleotide monomers
sugar
phosphate
nitrogen base
They store information
The instructions makes proteins
Examples: DNA & RNA
NUCLEIC ACIDS
very large linear molecules
made up of nucleotides containing C, H, N, O, P
store genetic information, help to make proteins
examples: DNA and RNA

12. DNA Structure What does DNA stand for?
What is the monomer for nucleic acids?
What is the structure of this monomer?
DeoxyriboNucleic Acid
nucleotide
The numbers are the positions of the carbons on the sugar.
(the 3’ end) 5 4 3 2 1
(the 5’ end)
N base
PO4
Sugar
PO4
N base
Sugar

13. A DNA NUCLEOTIDE 1. Phosphate Group 2. 5-Carbon Sugar (Dexoyribose)
3. Nitrogen Base
2. 5-Carbon Sugar (Dexoyribose)
1. Phosphate Group
2. 5-Carbon Sugar (Dexoyribose) 1. 2. 3.
3. Nitrogen Base H H2 H3 O C N P 1. 2. 3.

14. DNA Nucleotides A G T C Adenine Purines Guanine Thymine Pyrimidines
There are four nitrogen bases making up four different nucleotides. A
Adenine
Purines
Guanine G
N base T
Thymine
Pyrimidines
Cytosine C

15. Chargaff’s Base Pair Rules
Adenine always bonds with thymine. A T
The lines between the bases represent hydrogen bonds C G
Guanine always bonds with Cytosine.

16. Pairing DNA Nucleotides
What is the base pairing rule?
What is a nucleotide?
What would be the complementary nucleotide pairing? P
N-b
Nucleotide C S G
Rule A
Review slide. Make sure students can pick out the sugar, phosphate group, and nitrogen bases as well as know how the bases pair up (have them tell you the what the answers are before you animate it)
A to T A
C to G T G

17. 3’End
5’End
ladder shaped molecule
DNA DOUBLE HELIX

18. Purpose of DNA DNA contains our genetic code which codes for proteins.
It is our “blueprint”…all cells have the same blueprint, but only certain parts are looked at when building different cells

19. What is RNA? RNA stands for RiboNucleic Acid
DNA must have a “helper” molecule. (DNA is too fat)
sugar
phosphate
nitrogen base
RNA is a single stranded nucleic acid
made up of monomers called nucleotides

20. RNA Nucleotides B A C A - Sugar (ribose) B - Phosphate
C - Nitrogen base
nitrogen base
sugar
phosphate B
RNA is made of nucleotide subunits arranged in a single strand
Ask students which molecules are which (before you animate the answers) A C

21. RNA Nitrogen Base Sugar (ribose) Phosphate Group
Identify the parts of the RNA strand.
Nitrogen Base
Make sure students know the molecules located in RNA. Have the students notice that RNA is single stranded whereas DNA is a double helix.
Sugar
(ribose)
Phosphate Group

22. Rules for Base Pairing A U C G Adenine bonds with Uracil.
Guanine bonds with Cytosine.

23. DNA makes RNA C = G A = U 3’ DNA strand RNA strand 5’ DNA strand C G A
Teacher FYI – the transcription process moves from the 3’ end of DNA to the 5’ end and synthesizes an RNA strand of opposite polarity T A
RNA strand
5’ DNA strand

24. What is the function of RNA?
Carries the coded “message” of DNA.
Translates the “message” into proteins
3 Types of RNA
Messenger RNA (mRNA)
Transfer RNA (tRNA)
Ribosomal RNA (rRNA)
Ask students the function of RNA; they should recall this from the organic molecules unit.
Introduce the three types of RNA; you don’t need to give their functions here.
Messenger (mRNA)
Transfer (tRNA)
Ribosomal (rRNA)

25. Comparing DNA & RNA DNA RNA √ √ √ √ Sugar is deoxyribose
Sugar is ribose
Adenine base is present
Cytosine base is present √ √ √
Review the differences between DNA & RNA
Have them tell you the answers to each before you animate the answers √

26. Comparing DNA & RNA DNA RNA √ √ √ √ Guanine base is present
Thymine base is present
Uracil base is present
Shape is double helix √ √ √
Review the differences between DNA & RNA
Have them tell you the answers to each before you animate the answers √

27. Comparing DNA & RNA DNA RNA √ √ √ √ Shape is single stranded
Located in nucleus
Located in cytoplasm
Stores genetic information √ √ √
Review the differences between DNA & RNA
Have them tell you the answers to each before you animate the answers √

28. Comparing DNA & RNA DNA RNA √ √ √ √ √ Functions in protein synthesis
Composed of nucleotides
Instructions (template) for synthesis of proteins
Transcribes and Translates the template
More than one type √ √ √
Review the differences between DNA & RNA
Have them tell you the answers to each before you animate the answers
You will probably have to tell them the answers to the 1st, 3rd & 4th question on this slide since they don’t know about protein synthesis yet; it will be a good review at the end of the chapter though. √ √