1. Chapter 12 & 13 DNA and RNA

2. Timeline of the Discovery of DNA DO NOT COPY
1928 Griffith
Transformation of one type of bacteria into another
1944 Avery
DNA is the molecule responsible for transformation and makes up genetic material of cells.
1952 Hersey and Chase
Confirmed DNA is the molecule that makes up genetic material of cells.
Chargaff’s Rule
In DNA from all species, adenine = thymine and cytosine = guanine.
1950’s Franklin
X-ray diffraction photograph of DNA
1953 Watson and Crick
build a 3D model of structure of DNA

3. 1952 Hershey and Chase Studied viruses called bacteriophages.
Bacteriophage: virus that infects bacteria
Marked viruses with radioactive P and S, mixed with bacteria and tested for radioactivity. (Sulfur is part of protein and Phosphorus is part of DNA)
WHY??
DNA doesn’t contain sulfur and proteins doesn’t contain phosphorus
Marked with radioactive Phosphorus isotopes and sulfur isotopes

4. The Role of DNA
Store: Information: DNA stores information for genes that control patterns of development.
Copy: Before a cell divides, it must make a complete copy of every one of its genes
Transmit: the genetic information in a cell.

5. Nucleic Acids and Nucleotides (Review chapter 2.3)
Nucleic acids are long molecules found in the cell nucleus.
Subunit: Nucleotides
Nucleotides are made of:
Nitrogen base
Deoxyribose sugar
Phosphate group

6. Nitrogenous Bases and Covalent Bonds
DNA has four kinds of nitrogenous bases: adenine (A), guanine (G), cytosine (C), and thymine (T).

7. Chargaff’s Rules:
The percentages of adenine [A] = thymine [T]
and
The percentage of guanine [G] = cytosine [C].

8. Franklin’s X-Rays – Photo 51
British scientist Rosalind Franklin used saw DNA with x-ray

9. The Work of Watson and Crick
Watson and Crick built a model that explained the structure and properties of DNA.

10. Strands of DNA are held together by Hydrogen bonds
Hydrogen Bonding
Strands of DNA are held together by Hydrogen bonds

11. Base Pairing
Watson and Crick realized that base pairing explained Chargaff’s rule. It gave a reason why [A] = [T] and [G] = [C].

12. The Replication Process
Before a cell divides, it duplicates its DNA in a copying process called replication.
Each strand of the double helix of DNA serves as a template, or model, for the new strand.

13. The Replication Process
The two strands of the double helix separate, or “unzip,” allowing two replication forks to form.
As each new strand forms, new bases are added following the rules of base pairing. (A T and C G)

14. The Replication Process
Each DNA molecule resulting from replication has one original strand and one new strand.

15. The Role of Enzymes -“proofreads” new DNA strand.
DNA polymerase: joins nucleotides to produce a new strand of DNA
-“proofreads” new DNA strand.

16. Telomeres The tips of chromosomes are known as telomeres.
The ends of DNA molecules, located at the telomeres, are particularly difficult to copy.
Over time, DNA may be lost from telomeres each time a chromosome is replicated.
Telomerase:
1. adds short, repeated DNA sequences to telomeres
2. lengthens the chromosomes
3. Reduces likelihood that gene sequences will be lost during replication.

17. Replication in Living Cells
**Replication always occurs before cell division
Prokaryotes: have a single, circular DNA molecule in the cytoplasm. Replication starts from a single point and proceeds in two directions until the entire chromosome is copied.
Eukaryotes: have up to 1000 times more DNA and nearly all of the DNA is found in the nucleus. Replication starts in hundreds of places.

18. RNA & Protein Synthesis
Chapter 13

19. DNA = book of instructions that tells which proteins to make
13.1
DNA = book of instructions that tells which proteins to make
The path from genes to proteins has two steps:
Transcription—copying the DNA codes to make RNA
Translation—using the codes to make proteins

20. Ribonucleic Acid (RNA)
Long chains of nucleotides made by transcription
Most RNA is used for protein synthesis
Nucleotide Structure

21. DNA v. RNA DNA RNA 5 Carbon Sugar Deoxyribose (one less oxygen) Ribose
Nitrogen Bases
Adenine
Thymine
Guanine
Cytosine
Uracil
Phosphate
Same in both
Number of strands
Double strand
(base pairs)
Single strand
(single bases)
Size
100s of million base pairs
100s s of bases

22. Three Forms of RNA
Messenger RNA (mRNA) carries copies of the instructions for protein synthesis from the nucleus to the cytoplasm
Transfer RNA (tRNA) transfers the amino acids to the ribosomes in the order specified by the mRNA
Ribosomal RNA (rRNA) is part of the structure of ribosomes (where proteins are made)

23. Transcription DNA is read and a strand of RNA is created from it.
Segments of DNA are templates to produce complementary RNA molecules
DNA
RNA A U T G C

24. Transcription
RNA Polymerase: reads DNA during transcription, builds RNA
Promoters: sequences of DNA that show RNA polymerase where to attach (BINDING SITE).

25. RNA Editing
Introns: part of first draft of RNA that is cut out and discarded.
Exons: all other parts spliced together to form the final mRNA

26. Translation = Protein Synthesis
13.2
Translation = Protein Synthesis
mRNA (from transcription) is then translated by the ribosome.
tRNA brings the appropriate amino acids that are sequenced to create the protein.

27. Proteins (review Ch 2 pages 48-49)
Amino Acids (AA): about 20 different types; each with identical amino group and a carboxyl group and a unique side group
Polypeptide: long chains of amino acids formed when the amine of one AA binds with the carboxyl of next AA; order of AA determined by the mRNA code

28. The Genetic Code 4 letters: A, U, G, and C
64 possible 3 letter combinations from 4 letters (4 x 4 x 4 = 64)
Codon: 3 letter code found in mRNA; one AA per codon (and some AA have multiple codons)
Anticodon: 3 letter code found in tRNA that carries AA and is the complement of a codon

29. Reading codons (version 1)

30. Reading Codons version 2
Protein Synthesis Animation:

34. The Big Picture

35. Mutations Inheritable changes in genetic information Causes:
13.3
Mutations
Inheritable changes in genetic information
Causes:
Random Errors in replication
Stress
Physical Mutagens (x – ray, UV light)
Chemical Mutagens (pesticides, tobacco)

36. Types of Mutations 2 types of mutations:
13.3
Types of Mutations
2 types of mutations:
1. Gene Mutations (point and frameshift)
2. Chromosomal Mutations

37. Point Mutations Change in a single nucleotide in DNA Substitutions
Insertions
Deletions

38. Chromosomal Mutations
Change in number or structure of chromosomes
Deletion
Duplication
Inversion
Translocation

39. Effects of Mutations None Harmful Beneficial
Change has no effect on the AA inserted
Harmful
Disrupts normal cell function
Sickle Cell Anemia
Hemophilia
Cancer
Beneficial
Change increases variation in the species and improves chance of survival in changing environmental conditions
Pesticide resistant mosquitoes
Polyploidy plants

40. Prokaryote Gene Regulation
13.4
Prokaryote Gene Regulation
Proteins bind to parts of DNA to turn on/off transcription

41. Eukaryotic Gene Regulation
Much more complex than in prokaryotes
Important to cell differentiation in multi-cellular organisms
Influenced by the physical and chemical environment of the cell (example frog metamorphosis)