Honors Bio: Biochem 3 Pt. 2

Protein Synthesis

the process of making proteins (in cytoplasm)

RNA Transciption

copy DNA to RNA

RNA-polymerase

builds new RNA molecules in a 5 to 3 direction.

Template strand

only one side of DNA strand is read

Promoter

special sequence of letters; attachment point for RNA-polymerase

Upstream

section of DNA before gene to be described

Downstream

section of DNA being transcribed

Consensus sequence

most commonly used sequence of bases in a promoter

Strong promoters

match consensus closely and are transcribed often

Weak promotors

have variations in consensus sequence and transcribed less often or not at all

Termination loop

a sequence of self-complementary bases that fold up and knock the RNA-polymerase off the DNA molecule

Nuclear RNA (nRNA)

rough draft of RNA that stays in the nucleus to be further refined

Editing

a series of steps that modifies nRNA into functioning mRNA

Spliceosome

an enzyme complex that removes introns from the exons

Introns

junk or interrupting segments

Exons

good or expressed segements

CAP

provides an attraction point for the ribosome and protects the mRNA from enzymes in cytoplasm

Poly-A tail

"feed" the nucleases giving the mRNA time to be "read" and make proteins

Nucleases

enzymes in the cytoplasm

Nucleolus

the place in the nucleus where rRNA is found

Ribosomes

the site of protein synthesis

Cloverleaf pattern

3-D shape due to several sequences of self complementary bases

Messenger RNA (mRNA)

carries information on how to make proteins from DNA in the nucleus to the ribosomes in the cytoplasm (linear)

Ribosomal RNA (rRNA)

"site of protein synthesis", helps organize the "reading" of the mRNA and aids in the docking of tRNA to mRNA (structural 3-D molecule)

Transfer RNA (tRNA)

transports amino acids from cytoplasm to ribosome in the correct sequence according to the code carried by mRNA (structural 3-D molecule)

Translation

when tRNA (with help from the ribosome) reads the genetic code contained in the mRNA and "translates" the code and inserts the correct amino acids

Triplets

every 3 bases in DNA

Codons

every 3 bases in mRNA

Anticodons

last three bases in tRNA

Initiation

ribosome assembly

Start codon

AUG

Reading frame

correct three bases

A-site

accepts the new, incoming tRNA with its amino acid

P-site

where the growing polypeptide is "parked"

E-site

where the free tRNA "exits" the ribosome to go and pick up new a.a.

Elongation

building the growing polypeptide

Termination

ending transcription, one of three special stop codons attract a releasing factor that stops translation

Polysome/polyribosome

many ribosomes can attach to and read the same mRNA at the same time

Initiation codons

start/starter codons

Termination codons

stop codons; ends translation of mRNA by separating large and small subunits of the ribosome

Redundant Codes

many amino acids have more than one codon

Universal code

the same triplet sequence is used by all living organisms

Recombinant biotechnology

transplanting genes among unrelated organisms

GMO's

genetically modified organisms

Gene

a segment of DNA that transcribes into a segment of RNA

Mutation

a sudden change in genetic makeup

Point mutation

a change in the base sequence of a DNA molecule/gene.

Chromosome mutations

change in number or structure of chromosomes (result of cell division error)

Causes of mutations

-High energy radiation (nuclear radiation, UV rays, X Rays)

-Biological (viruses)

-Chemicals (industrial, food preservatives/additive)

Gene expression

when a gene is transcribed

Gene regulation

what controls the expression of a gene

Jacob-Monod Hypothesis

studied the induction of the enzyme, lactase, in bacterial cells in the presence of lactosef

Operon

an operating unit of DNA that codes for a specific mRNA and is made up of promoter, structural gene, operator

Structural gene

segment that codes for the RNA molecule.

Operator

binding site for repressor

Regulator gene

codes for mRNA that produces a repressor protein that binds to the operator and prevents the structural gene from being read

Repressor

prevents a structural gene from being read

Gene activation

turning a gene on

Inducer

binds to the repressor, altering its shape, so that it cannot bind to the operator (key)

Histones

proteins that cover the DNA found in nucleus