Studied by 16 people
T.H. Morgan
associated phenotype with specific chromosome
Griffith
transforming principle
Avery, McCarty & MacLeod
experimental evidence that DNA was the genetic material
Hershey and Chase
confirmed DNA is a transforming factor
Chargaff
DNA composition, base pairing rules
Watson & Crick
developed double helix model of DNA
Meselson & Stahl
showed how DNA replicates
Central Dogma
DNA →(transcription)→ RNA →(translation)→ Protein
DNA base pairing
A-T , C-G
RNA base pairing
A-U , C-G
DNA replication models
(photo)
Origin of Replication
sites where replication begins
Replication Process
(photo)
Helicases
enzymes that untwist the double helix at the replication forks
Single-strand binding proteins (SSBPs)
bind to and stabilize single-stranded DNA until it can be used as a template
Topoisomerase
corrects “overwinding” ahead of replication forks
Primase
reads the DNA code and synthesizes an RNA primer (5-10 RNA nucleotides long)
DNA polymerase III
adds DNA nucleotides to the 3' end of the primer (assembles in the 5' to 3' direction)
DNA polymerase I
replaces RNA primers with DNA nucleotides
DNA Ligase
seals fragments
Leading Strand
synthesized by DNA polymerase, moves continuesly toward replication fork
Lagging Strand
series of Okazaki Fragments, joined by DNA Ligase
Nuclease
replaces damaged strech of DNA
Telomeres
nucleotide sequences at the ends of eukaryotic chromosomes
Telomerase
enzyme that catalyzes the lengthening of telomeres in germ cells
3 Stages of Protein Synthesis
Transcription, mRNA Processing and Modification, Translation
Transciption
the synthesis of RNA under the direction of DNA
Transcription Initiation
RNA polymerase attaches to the promoter region of the DNA, RNA polymerase unzips DNA and initiates transcription
Transcription Elongation
RNA polymerase attaches ribonucleotides in the 5’--> 3’ direction
Transcription Termination
RNA polymerase detaches from DNA, releasing RNA strand
mRNA Processing
Addition of 5’ cap, Addition of poly-A tail, RNA splicing
Spliceosome
Introns are removed, exons are spliced together
Intron
noncoding region
Exon
coding region
Translation
the synthesis of a polypeptide, which occurs under the direction of mRNA
Translation Initiation
the first tRNA with an amino acid temporarily binds to the first site
Translation Elongation
the second tRNA molecule attaches to the second site of translation, amino acid from the first tRNA is transferred to the amino acid on the second tRNA, the first tRNA exits, the ribosome moves, a new tRNA enters
Translation Termination
release factor enters, polypeptide is released
Point mutation
single base change or base pair substitution
Silent mutation
no amino acid change
Missense mutation
changes amino acid
Nonsense mutation
change to stop codon
Frameshift mutation
insertion or deletion that changes the reading frame
Operons
a stretch of DNA that includes the operator, the promoter, and the genes that they control
Operator
“switch” in a segment of DNA, positioned within the promoter
Repressor
protein that switches operon off
Corepressor
molecule that cooperates with a repressor protein to switch an operon off
Repressible operon
usually on; binding of repressor to the operator shuts OFF transcription (trp operon)
Inducible operon
usually off; an inducer inactivates the repressor and turns ON transcription (lac operon)
TRP Operon
default on, when tryptophan is present it bind to trp repressor and turns operon off
LAC Operon
default off, inducer molecule inactives repressor
Repressible Enzyme
funtion in anabolic pathways
Inducible Enzyme
function in catabolic pathways
Types of Eukaryotic Gene Regulation
Chromatin modification, Regulation of transcription, RNA processing, mRNA degradation, Translation, Protein processing and degradation
Chromatin Modification
genes in highly compacted chromatin are generally not transcribed
Histone acetylation
loosens chromatin structure, Promotes transcription
DNA methylation
addition of methyl groups condenses chromatin, Inhibits transcription
Transcription factors
proteins that help RNA polymerase to initiate transcription
Alternative RNA splicing
different mRNA molecules are produced from the same primary transcript
mRNA degradation
Life span of mRNA molecules in the cytoplasm is a key to determining protein synthesis
Protein Processing and Degradation
After translation, chemical groups get added to proteins for further specialization, Proteins are folded by chaperonins
Non-Coding RNA’s
significant amount of the genome may be transcribed into non protein-coding RNAs
Nucleic Acid Hybridization
base pairing of one strand of a nucleic acid to a complementary sequence on another strand
Genetic Engineering
the direct manipulation of genes for practical purposes
Gene cloning
Process of producing multiple copies of specific DNA segments, making recombinant DNA in the process
Plasmids
small circular DNA molecules that replicate separately from the bacterial chromosome
Recombinant DNA
DNA from two different sources, often two species, combined **into the same DNA molecule
Restriction Enzymes
bacterial enzymes that cut DNA at specific sequences called restriction sites
Sticky Ends
most useful cuts in a staggered way
Polymerase Chain Reaction (PCR)
can produce many copies of a specific target segment of DNA
PCR 3 Step Cycle
Heating, Cooling, Replication
Gel Electrophoresis
An electrical current is applied that causes charged molecules to move through the gel, molecules are sorted into "bands" by their size
Restriction fragment analysis
DNA fragments produced by restriction enzyme digestion are sorted by gel electrophoresis
Short tandem repeats (STRs)
variations in the number of repeats of specific DNA sequences
CRISPR-Cas9
new technique for editing genes, Cas9 = bacterial protein
Note 
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