5.4/5.5 - DNA translation

ribosome structure

composed of 2 subunits (lg and sm)

primarily made of ribosomal RNA (rRNA) and proteins

large subunit has an intricate atomic structure

mRNA and protein synthesis

mRNA directs protein synthesis but does not have a direct base-pairing relationship with amino acids

tRNA (transfer RNA) Is required

tRNA

single-stranded RNA that folds into an L-shaped structure due to hydro bonding

anticodon pairs with codon on mRNA - at opposite end amino acid attaches to the tRNA based on the anticodon

aminoacyl tRNA synthetases

enzymes that attach to the correct amino acid to the tRNAn based on the anticodon

redundancy

multiple codons can code for the same amino acid

each codon corresponds to only one amino acids, ensuring no ambiguity

codons in groups of 3

provide sufficient combos

64 combos for 20 amino acids

reading frame

correct grouping of nucleotides is essential for accurate protein synthesis

shifting reading frame changes the meaning

initiation (translation)

small ribosomal subunit binds to 5’ end of the mRNA

scans to find start codon (AUG)

lg subunit joins and first tRNA (methionine) enters ribosome

elongation (translation)

ribosome moves along mRNA, reading codons

each codon is paired with comp tRNA and amino acids are linked together to form polypep chain

termination (translation)

when stop codon is reached - translation ends

ribosome releases mRNA and newly synthesized protein is complete

ribosome location

translation begins in cytosol - can move to rough ER

cytostolic proteins (ribo location)`

made my cytostolic pros

secreted proteins (ribo locations)

membrane proteins are syntehsized on ribos on rough er

post translation modification

proteins can have added phosphates, sugars, or lipids

crucial for final function

gene expression reg

cells regulate which genes are expressed to conserve energy

promoter sequences

near genes - control transcription w/ transcription factors binding to initiate process

mutations/repressor proteins can block transcriptionn by interfere w/ transcript. binding

enhancer sequences

reg gene expression by binding additonal proteins

gene networks

one gene can regulate many others (ex. hox genes)