1. Chapter 14

2. History of the “Gene”
DNA was first described in 1869 by Johannes Miescher
Frederick Griffith (1928) observed harmless bacteria “transformed” into lethal ones
Hereditary information must be transmitted in the molecule
Hereditary material encodes information required to build a new individual
Proteins and DNA were candidates.
Avery MacLeod and McCarty(1944) confirmed that the “transforming principle” was a nucleic acid
In the Hershey and Chase (1952) established that DNA transmits hereditary information

4. Nucleic acid review DNA is a polymer of nucleotides
Five-carbon deoxyribose sugar
Phosphate groups
Nitrogen-containing base: Adenine, Thymine, Guanine, Cytosine
DNA molecules can be hundreds of millions of nucleotides long
DNA in a single human cell is about 2 meters long
Chromosome: structure that consists of DNA and associated histone proteins

6. Discovering the DNA Structure
1950: Erwin Chargaff’s
first rule: Amount of A equal T and G equals C
second rule: Each species differs in its A to G ratios
1950s: Rosalind Franklin made x-ray diffraction image of DNA
James Watson and Francis Crick propose that DNA is a double helix
Two sugar–phosphate chains running in opposite directions, and paired bases inside
Base pairs held by hydrogen bonds
A to T
G to C

7. Replication Cell duplicates its chromosomes by DNA replication
Enzymes break the hydrogen bonds that hold the double helix together
DNA polymerases attach to each strand and begin DNA synthesis
The enzyme DNA ligase seals any gaps so the new DNA strands are continuous

8. Replication errors and repair
Mistakes occur during DNA replication
Replication errors may occur after a cell’s DNA gets broken or damaged
DNA polymerases also proofread their work
When repair mechanisms fail, an error becomes a mutation
Mutations that occur during egg or sperm formation can be passed to offspring
Not all mutations are deleterious

9. Chapter 15 Genes and Proteins

10. The “Central Dogma” of Biology
The DNA sequence of a gene guides the assembly of an RNA or protein product
Transcription and translation are part of gene expression
RNA is a single-strand chain of nucleotides
Unlike DNA, the sugar is a ribose and has uracil instead of thymine
Messenger RNA (mRNA): specifies order of amino acid sequence
Ribosomal RNA (rRNA): component of ribosomes
Transfer RNA (tRNA): carries amino acids to a ribosome for protein synthesis

12. Transcription RNA polymerase attaches to a promoter
Starts adding RNA bases
G pairs with C, T pairs with A,
A pairs with U (uracil)
Transcription ends at the terminator

13. After Transcription
Eukaryotic genes contain sequences called introns which are removed
Remaining sequences of RNA are called exons
Alternative splicing, allows exons to be rearranged into different combinations
RNA also gets a guanine cap and poly-A tail

16. Translation
mRNA’s protein-building is encoded by sets of three nucleotides called codons
Translation, the codon sequence is decoded into a polypeptide of amino acids
Ribosomes consists mainly of rRNA
rRNA catalyzes peptide bonds between amino acids
The first AUG in an mRNA: signal to start translation
UAA, UAG, and UGA: signals that stop translation

18. Translation (cont)
Translation begins in the cytoplasm when a small ribosomal subunit binds to the mRNA
The anticodon of a special initiator tRNA pairs with the start codon of the mRNA
Ribosome begins to assemble a polypeptide
Another tRNA joins the complex pairs with the second codon
The ribosome catalyzes peptide bond between first two amino acids
Ribosome moves to the next codon

19. Chapter 16 Gene Regulation

20. Epigenetic Control
Gene expression is controlled is response to the environment.
Cells use ~10 percent of its genes at one time
Only DNA that is unwound from histones are accessible to RNA polymerase.
At the highest level of regulation

22. Transcription factors:
Repressors: block promoters
Activators: bring RNA polymerase to the promoter

23. Post-transcriptional modification can affect the form of a protein
Alternative splicing
RNA interference: Translation of mRNA is shut down by microRNA
Post-translational modifications inhibit, activate, or stabilize proteins
Many polypeptide chains must be modified before they become functional

25. Chapter 17

26. Biotechnology
Gel Electrophoresis
PCR
Transgenics

28. Genome Mapping

29. DNA sequencing
Replication occurs with added bases that stop replication (ddNTP.
A mixture of strands are created each one with different terminating ddNTP
Each ddNTP has fluorescent compound which is observed through gel electrophoresis