1. DNA and RNA
Chapter 12

2. Hereditary Material Genes are protein codes.
Our genes are on our chromosomes.
Chromosomes are made up of DNA.
Genes are composed DNA!
{Ask students where the chromosomes are in this picture. Or ask them where the DNA is. Remind them that the mitochondria also have DNA.}

3. Chromosome Structure
Chromatin is tightly coiled around proteins called histones.
DNA and histone molecules form a beadlike structure: nucleosome
Nucleosomes create the supercoils
of DNA in a chromosome.

4. Chromosome Structure of Eukaryotes
Nucleosome
Chromosome
DNA
double
helix
Coils
Supercoils
Each cell has about 2 m of DNA.
The average human has 75 trillion cells.
The average human has enough DNA to go from the earth to the sun more than 400 times.
DNA has a diameter of only m.
Histones

5. Structure of DNA In eukaryotes, DNA is found in the NUCLEUS of cells.
DNA is made up of a series of monomers called nucleotides.
Nucleotide structure:
1. 5–carbon sugar: Deoxyribose
2. Phosphate group
3. Nitrogenous base
DNA is a twisted-ladder called a
DOUBLE HELIX!

6. DNA Nucleotide O O=P-O N CH2 O C1 C4 C3 C2 Phosphate Group
Nitrogenous base
(A, G, C, or T)
CH2 O C1 C4 C3 C2 5
Sugar
(deoxyribose)

7. Nitrogenous Bases Double ring PURINES Adenine (A) Guanine (G)
Single ring PYRIMIDINES
Thymine (T)
Cytosine (C)
A or G
T or C

8. Chargaff’s (Base Pairing) Rule
Adenine must pair with Thymine
Guanine must pair with Cytosine
The bases form weak hydrogen bonds
Why do they pair together this way? T A G C

9. DNA Double Helix “Rungs of ladder” Nitrogenous Base (A,T,G or C)
“Legs of ladder”
Phosphate &
Sugar Backbone

10. DNA Structure Nucleotide Hydrogen bonds Sugar-phosphate backbone Key
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)

11. DNA Replication Occurs during cell division.
Helicase enzyme “unzips” the molecule of DNA, breaking the hydrogen bonds.
Free-nucleotides in the nucleus will be bonded with its complementary base.
DNA polymerase helps to bond the nucleotides together and check for errors.

12. DNA Replication Section 12-2 Original strand DNA polymerase New strand
Growth
DNA polymerase
Growth
Replication fork
Replication fork
Nitrogenous bases
New strand
Original strand

13. DNA Replication

15. The Scientists
Griffith – one strain of bacteria was “transformed” into another strain.
Avery – found that DNA was the transforming factor.
Hershey and Chase – DNA is the genetic material.
Watson and Crick – discovered the molecular structure of DNA.

16. Griffith’s “Transformation” Experiment

17. Avery’s experiment isolated the element that caused the bacterial to become lethal…DNA

18. Hershey-Chase Experiment
Section 12-1
Bacteriophage with phosphorus-32 in DNA
Phage infects bacterium
Radioactivity inside bacterium
Bacteriophage with sulfur-35 in protein coat
Phage infects bacterium
No radioactivity inside bacterium

19. Chargaff and Franklin Chargaff Rosalind Franklin
Percentages of guanine and cytosine bases are almost equal in any sample of DNA
Same is true of adenine and thymine
DNA in all instances and from all organisms followed this rule
Rosalind Franklin
X-Ray diffraction showed that
DNA was twisted into a
double helix.

20. RNA and Protein Synthesis
Section 12-3

21. RNA Long, single strand of nucleotides.
Nitrogen bases: A,U,G,C no Thymine!
Sugar: Ribose
Found in cytoplasm and nucleus
Types: messenger, transfer, ribosomal
Function: Involved in the synthesis of protein molecules.

23. Protein Synthesis occurs in two phases:
TRANSCRIPTION
TRANSLATION

24. Transcription Location where it occurs: Nucleus
RNA polymerase will unwind DNA at the region to be transcribed.
It locates and binds at the promoter.

25. mRNA is then made by base-pairing: A-U, G-C, T-A, C-G
If DNA sequence is: GATTACA
Then mRNA sequence is: CUAAUGU
When finished, mRNA leaves the nucleus and goes to the cytoplasm.

26. Transcription Section 12-3 RNA polymerase DNA RNA
Adenine (DNA and RNA)
Cystosine (DNA and RNA)
Guanine(DNA and RNA)
Thymine (DNA only)
Uracil (RNA only)
RNA polymerase
DNA
RNA

28. Translation Location: Cytoplasm mRNA finds a ribosome
Ribosome reads strand for the start “codon”
A codon is a mRNA triplet. Ex: AUG, UUC, etc
Start codon is: AUG
Transfer RNA’s bring
amino acids to
ribosome.

29. Translation continued…
tRNA’s anticodon bonds with mRNA codon.
mRNA codons AUG UAA CGC
tRNA anticodons UAC AUU GCG
Amino acids connected with peptide bonds.
When a “Stop” codon is reached. Protein is released from ribosome.

30. Translation
Section 12-3
Animation

32. How to Interpret m-RNA’s Code:
Each 3 nitrogen base sequence is called a CODON.
Each codon specifies for a particular amino acid.
AUG codon starts the initiation of the protein and codes for the amino acid methionine.
Stop codons do not code for any amino acids ending the protein chain.
A polypeptide is a chain of amino acids joined with peptide bonds – aka a PROTEIN!

33. Codon Chart #1
Section 12-3

34. Codon Chart #2

35. Methionine, Asparagine, Leucine
Let’s Practice!
DNA: TACTTGGAT
mRNA: AUGAACCUA
tRNA: UACUUGGAU
Amino Acid squence:
Methionine, Asparagine, Leucine

36. Mutations
Section 12-4

37. Mutations Changes that occur in the DNA Two types: 1. Gene mutations
2. Chromosomal mutations
Many mutations are harmless
Pros: increase adaptation or survival
Cons: some can be lethal or debilitating

38. Gene Mutations Changes that occur in a single gene.
Point mutations: one nucleotide that affects one amino acid.
(substitutions produce point mutations)
Frameshift mutations: involve the reading of the DNA or m-RNA strand; many amino acids are affected.
(insertion or deletions produce frameshift mutations)

39. Gene Mutations Frameshift mutations Point mutation: Substitution
Insertion
Deletion

40. Chromosomal Mutations
Whole chromosome is affected.
Four types:
1. Deletion – loss of material
2. Duplication – addition of material
3. Inversion – rearrangement of material
4. Translocation – switching material with another chromosome

41. Chromosomal Mutations
Deletion
Duplication
Inversion
Translocation