1. DNA and RNA
Ch 12

2. DNA Deoxyribonucleic Acid
Macromolecule responsible for the transmission of genetic material between generations
What is the molecular structure???

3. DNA Structure Must Have 3 Characteristics
1. Composed of Genes
2. Genes have to carry information from generation to generation
3. DNA must be able to copy itself easily

4. Finding the Structure of DNA
1928 = Griffith
Studied disease causing bacteria
Found that bacteria pass on the ability to cause disease to their offspring (inheritance)
1944 = Avery
repeated Griffith’s experiment
discovered that DNA is what stores and transmits genetic information

5. Finding the Structure of DNA
1952 = Rosalind Franklin
used X-Rays to discover that DNA is a double helix w/ nitrogen bases in the center
1952 = Chargaff
discovered that the nucleotides that make up DNA are in equal proportions
A = T and G = C

6. Finding the Structure of DNA
1953 = Watson and Crick
credited with discovering the structure of DNA
used Franklin’s and Chargaff’s findings to build a model on their own
Published their results 1st = Nobel Prize

7. The Structure of DNA 1. Made up of Nucleotides
2. Shaped like a double helix (twisted ladder)
3. Hydrogen bonds hold it together
4. The rungs of the ladder are paired nitrogen bases

8. Nucleotides Bonded together to form DNA 3 Parts of a Nucleotide
1. 5-Carbon Deoxyribose Sugar
2. Phosphate Group
3. Nitrogen Bases (adenine, guanine, thymine, cytosine)

9. Nitrogen Bases Purines = 2 carbon rings (adenine and guanine)
Pyrimidines = 1 carbon ring (cytosine and thymine)
Adenine always bonds to Thymine (A - T)
Guanine always binds to Cytosine (G - C)

10. Prokaryotic vs. Eukaryotic DNA
Prokaryotic DNA
plasmid shaped (circular chromosome)
located in the cytoplasm
Eukaryotic DNA
long strands of DNA and proteins compacted together
1000x’s longer than prokaryotic DNA
located in the nucleus

11. DNA Replication
Nitrogen base pairing allows the DNA to make a copy of itself
Strands can both be used to make identical copies of DNA = complimentary strands

12. DNA Replication Process
1. An enzyme unzips the DNA (breaks the hydrogen bonds between base pairs)
2. Another enzyme attaches new base pairs to each strand (matches A to T and G to C)
3. Another enzyme proofreads the DNA and checks for any mistakes in base pairing
4. The last enzyme seals all the new hydrogen bonds between the new base pairs
Result = 2 Complimentary Strands

13. Replication Animation

14. Sample Replication Problems
Original Strand = A T C G A T C
Complimentary =
Org. Strand = T C G A C T A
Comp. Strand =
T A G C T A G
A G C T G A T

15. RNA and Protein Synthesis
Chapter 12-3

16. Central Dogma
DNA carries the genetic code and transcribes an RNA copy of the code
The RNA copy is translated by ribosomes to make protein
DNA RNA Protein 1 2
Transcription
Translation

17. Genes Coded DNA instructions for making a protein (recipe)
A specific sequence of DNA
DNA to RNA to Protein

18. Why do we need RNA if DNA holds all the genetics?
DNA must be protected…
If DNA is damaged
then the coding sequence is changed
then a mutation occurs
Then…

19. What is RNA? Ribonucleic Acid Sugar = Ribose not deoxyribose
Single stranded instead of double stranded
Uracil (U) instead of Thymine (T)
Made from a strand of DNA

20. 3 Types of RNA
Messenger RNA (mRNA) = carry the instructions for making amino acids into proteins
Ribosomal RNA (rRNA) = make up ribosomes
Transfer RNA (tRNA) = transfers the amino acids to the ribosomes to be made into proteins

21. Making a Protein
Step #1 = Make a RNA strand from a sequence of DNA (transcription)
Step #2 = Use the RNA strand to make a specific protein (translation)

22. Transcription
The process by which a piece of DNA is copied to make a complimentary RNA strand
Requires several enzymes
Occurs within the nucleus

23. Transcription Process
1. An enzyme unzips a portion of the DNA
2. An enzyme joins base pairs to one of the strands (U instead of T) to make mRNA
3. The new strand of mRNA is detached
4. An enzyme joins the DNA back together
5. Junk mRNA (introns) are deleted and the mRNA that will be expressed (exons) stays
link

24. Protein Synthesis/Translation
The mRNA is used to assemble amino acids into proteins
20 possible amino acid = make billions of different combinations
Occurs on the ribosome

25. Translation Process link/m_biology/animation/gene/gene_a3.html
1. mRNA attaches to the ribosome
2. Every 3 letters in a mRNA is a codon and specifies a specific amino acid
3. The tRNA’s carry the amino acids to the mRNA
4. Each tRNA has an anticodon that bonds to a specific codon sequence on the mRNA
5. The amino acids are bonded together to form a polypeptide (protein)
link/m_biology/animation/gene/gene_a3.html

26. Genes and Proteins Genes = instructions for making proteins
Proteins = make up enzymes = control all processes in the cell/body
*** Take Home Message ****
PROTEINS ARE IMPORTANT!!!!!
linkAP1302

27. How to do the homework problems:
Given = DNA Strand
1. Make a complimentary mRNA strand
from the DNA strand. U instead of T
2. Divide the mRNA into codons (3’s)
3. Find the corresponding amino acid using
Fig on pg (First Letter
Middle)
4. Always start at AUG and end at UGA,
UAA, or UAG

28. Example Problem: DNA = T A C T T T A C G A C T
mRNA = A U G A A A U G C U G A
Codons = AUG – AAA – UGC – UGA
Amino Acids = Start – Lysine – Cysteine – Stop