AP BIO unit 6

T.H. Morgan

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