1. DNA, RNA & Protein Synthesis
Chapters 12 & 13

2. The Structure of DNA

3. A little History Year Scientist(s) Discovery 1928 Frederick Griffith
Bacteria transfer genetic material from cell to cell.
1944
Oswald Avery, Colin Macleod & Maclyn McCarty
Griffith had discovered DNA!
1950
Erwin Chargaff
Of the four possible nucloetides: As = Ts & Gs = Cs.
1952
Alfred Hershey & Martha Chase
Genetic material in viruses is also DNA.
Rosalind Franklin
Demonstrated that DNA is a helix.
1953
James Watson & Francis Crick
DNA is a double helix.
2000
Craig Venter & Francis Collins
Sequenced human DNA.

4. DNA In prokaryotes (no nucleus), DNA is circular.
In eukaryotes, DNA is on the chromosomes in the nucleus.

5. Structure of DNA
Double-stranded helix
Linked nucleotides

6. Nucleotide Parts Sugar - deoxyribose
Phosphate group (has element phosphorous)
Nitrogenous base
Sugar and phosphate make the sides.
Bases make the rungs.

7. Nucleotide Types Adenine (A) Thymine (T) Cytosine ( C ) Guanine (G)
A bonds with T
G bonds with C
Called complementary base pairing

8. DNA Replication

9. DNA Replication When does it happen?
Before cell division (mitosis or meiosis)
Where does it happen?
In the nucleus

10. DNA Replication: Step 1
Enzyme (DNA Polymerase) unwinds DNA

11. DNA Replication: Step 2
Enzyme attaches free nucleotides to the original strands until both strands are copied.

12. DNA Replication: Step 3
Replication occurs in many spots along the DNA until all parts are copied.
Two identical strands are made.
Now cell division can occur!

13. Replication in Different Cells
In prokaryotes: Starts at a single point and proceeds in two directions until the entire chromosome is copied.
In eukaryotes: Begins at many places and proceeds in two directions until the entire chromosome is copied.

14. RNA

15. Genes Section of DNA with the instructions to make 1 protein.
Found in the nucleus.

16. Proteins Many amino acids linked together.
Click here for animation -> XX
Many amino acids linked together.
Proteins are made in the cytoplasm.

17. Proteins are made in the cytoplasm by ribosomes, but the instructions for doing this (the DNA) can’t leave the nucleus.

18. A single-stranded copy of DNA.
How can this work???
RNA
A single-stranded copy of DNA.

19. DNA vs. RNA RNA DNA Chain of nucleotides. Sugar is ribose.
Single-stranded.
Bases are A,U,G,C.
(U = uracil.)
DNA
Chain of nucleotides.
Sugar is deoxyribose.
Double-stranded.
Bases are A,T,G,C.

20. Types of RNA Transfer RNA (tRNA) Messenger RNA (mRNA)
Brings amino acid to the ribosome for protein assembly.
Ribosomal RNA (rRNA)
Inside ribosome. Helps with translation.
Messenger RNA (mRNA)
Copies DNA in the nucleus.

21. To go from DNA to a Protein, there are two steps:
Transcription- mRNA makes copy of DNA
Translation- protein is made from mRNA

22. Transcription: mRNA copies DNA
Step 1: enzyme (RNA Polymerase) unwinds DNA
promoter: regions of DNA where the enzyme binds
Step 2: mRNA bases make a copy of DNA

23. Transcription (Part 2)
Step 3: introns (bad bases) are removed, exons (good bases) are spliced together
mRNA = AUACGUAC
now = AUCUAC
Step 4: cap and tail are added
Step 5: mRNA leaves the nucleus for the cytoplasm.
Link <- Click Here for Animation

24. Ribosomes & Protein Synthesis

25. Codons
A section of three mRNA bases in a row that codes for one amino acid.

26. Anticodons
The corresponding tRNA that carries the amino acid.

27. Translation: the mRNA is translated into a protein
Animation<- Click Here for Animation -> XX
1.) Ribosome finds the start codon, AUG, on mRNA.
2.) The corresponding anticodon on the tRNA binds into place.
3.) The ribosome reads the next codon & its corresponding anticodon binds.
4.) The ribosome bonds the two amino acids on the tRNA together. The tRNA lets go.
5.) This continues until a stop
codon is reached. Then the
last tRNA & ribosome fall off.
6.) The amino acid chain folds
into its proper structure.

28. The central dogma of molecular biology= DNA-> RNA-> protein
gene expression: process by which a gene produces its product, which carries out its function

29. Gene Regulation & Expression

30. How do cells regulate gene expression?
Proteins bind to sections of DNA that control transcription.
More complex in eukaryotes because cells are specialized.

31. Differentiation
When new cells become specialized in structure & function during embryonic development.
In humans cells, this occurs 4 days after fertilization.

32. Mutations

33. What are mutations?
Changes in the DNA sequence that changes the protein it codes for.
Two Types:
1.) Chromosomal Mutations
2.) Gene Mutations

34. Chromosomal Mutations
Result from changes in a whole chromosome.
1.) gene deletions
2.) gene duplications
3.) gene inversions
4.) translocations

35. Gene Deletion
Parts of a chromosome break and rejoin, with a gene missing.
Ex: Cris-du-chat Syndrome

36. Gene Duplication
Most duplications have no phenotypic consequences.

37. Inversion
Part of a chromosome becomes oriented in the reverse of its usual direction.
Usually no phenotypic consequences.

38. Translocation
Part of a chromosome breaks off and attaches to a nonhomologous chromosome.
Can lead to nonviable zygotes.

39. Point Mutations Occur at a single point in the DNA.
Usually one nucleotide is substituted for another, changing an amino acid.
Ex: Sickle Cell Anemia

40. Frameshift Mutations
Type of point mutation where an extra nucleotide is inserted or deleted, shifting the reading of codons, resulting in changes to ALL of the amino acids.
Ex: Huntingdon’s Disease
What is Mutation?
The Outcome of Mutations->
Link

41. Mutagen An agent that causes a change in DNA.
Ex: smoke, high energy radiation (X rays, UV light, nuclear radiation), chemicals (dioxins, asbestos, benzene, cyanide, formaldehyde), and high temperatures.
Note: In some cases, a gene mutation may have positive effects leading to evolution.