genetic code and translation

All protiens are

polymers composed of amino acids linked end to end. there are 20 amino acids

amino acids

monomers made of polypeptides of functional polypeptide is a portien

how are amino acids joined

amino acids in protiens are joined togethere by peptide bonds to form polypeptides

polypeptide

portien contains of one or more polypeptide chain

primary structure

the protiens is its seuqence of amino acids peptide bonds between the carbonyl of the first amino acid and amine group of the next amino acid

secondary structure

is the interaction between amino acids cause the primary structure to fold inot a secodnary structure such as a alpha helix or a beta pleated sheet. its formed mostly by hydorgen bonds between the various amino and carboxyl group of the core amino acid

core amino acid

an amino acid that is central to the structure of proteins, including the amino and carboxyl groups necessary for forming peptide bonds.

tertiary structure

the secondary structure folds further ino a tertiary structure 3d shape of protien that is formed by interactions between the R groups

quaternary structures

only some protiens do this and two or more polypeptide chains may associated to create a qeusternary structure

codons

sets of 3 nucleotides that encode for a single amino acid. its the absic unit of the genetic code

genetic code

RNA is translated inot polypeptide according to the genetic code

translation reads along

5’to3’ and it always begins on AUG codon (MET a.a)

Unambiguous

Each codon codes for only one amino acid.

Degenerate

Multiple codons can code for the same amino acid.

Universal

(almost): Nearly all organisms use the same code. strong selection for conservation

synonomous

baiscally similar meanng to degenerate and multiple codons that specify for the same a.a

tRNAs what purpose according to a.a

are the amino acid attachement site on 3’ side

tRNA =

transfer RNA; brings amino acids to ribosome

anticodon arm

is a structural region of the tRNA molecule that contains teh anticodon its a hairpin shaped it interacts with the RNA template in translation

Codons are on

mRNA

anticodons are on

tRNA

Anticodon/codon

Anticodon matches codon complementarily and antiparallel.

Codon 5’ AUG 3’ → Anticodon 3’ UAC 5’.

the whole mRNA

is no translated both UTR on the 5’ and 3’ before the start codon and after the stop codon

Start Codon in eukaryotes and prokaryotes

Always AUG, which also codes for methionine in eukaryotes.

In bacteria: fMet (formyl-methionine) is used always all bactrial has the at one end unless modifed later.

stop codon

doesnt code for any a.a. AKA termination,noncense codon

if a codon is not a stop codon it is

sense codon

reading frame

is a way of dividing seq. of nuclotides inot consecutive, non-overlapping triplets (codons) Start codon sets the reading frame.

Changing the start changes the entire protein made (often nosnsense or nonfunctional).

the only one reading frame thats chosen is teh one that starts at the start codon

how many reading frames are in a sequence

A sequence has 3 possible reading frames on one strand (6 total with reverse).

one 3-5 adnd the other 5-3

N (amino) end (terminus)

was the first amino acid translated

c (carboxyl) terminuns

is the latest Amino acid translated and its the closest to the ribosome

Ribosome Structure

Made of rRNA + protein = ribonucleoprotein.

Two subunits: Large + Small

Translation sites:

A (aminoacyl)

P (peptidyl)

E (exit)

A site

New tRNA enters.

P site

Peptide bond is formed.

E site

Empty tRNA leaves.

tRNA charging

attatching the correct amino acid by aminocyl-tRNA synthetases ( there is only 1 per a.a.) to its corresponding tRNA

what happens if the the amino aicid is nto attatched ot the right tRNA

the wrong protien gets made and becomes nunfucntinal most likely

Initiation

Bacteria:

Small ribosomal subunit binds to Shine-Dalgarno sequence near start codon.

Initiator tRNA (fMet-tRNA) binds AUG.

Large subunit joins.

Initiation

in bacteria

Small subunit + Met-tRNA bind to 5’ cap.

Scans to first AUG.

AUG is often in a kozak sequence for recognition.

Monocistronic

(Eukaryotes): 1 mRNA → 1 protein.

Polycistronic

(Prokaryotes): mRNA can encode multiple proteins.

Prokaryotes need

precise Shine-Dalgarno recognition to avoid starting at the wrong AUG.

but eukaryotic organisms mechanism

limits cell teo 1 gene per mRNA (initialrtes at 1st appropritate AUG)

translocation`

Ribosome moves forward one codon the tRNAs dont move and the e site exits with empty tRNA

Termination what happens after hitting stop codon

Protein and ribosome detach.