fundamentals of DNA, RNA and proteins

• double stranded helix • complementary base pairs • nuecleotide bases • hydrogen and phosphodiester bonds • antiparallel

• stretch of DNA that carries coded info for a sequence of amino acids to build a protein

• introns • exons • promoter region • untranslated sequences • other regulated sequences

• tightly packed, organised, accessible • coiled around histones • packed in chromosomes • 46 chromosomes in 22 pairs of autosomes and 2 sex chromosomes

centromere, p arm (at the top), q arm (at the bottom)

the arms are fairly equal in size

the p arm is shorter than the q arm

there is no visible p arm

• DNA primase that uses DNA nucleotides synthesis the primers on the lagging strand • DNA ligase joins the 3’ hydroxyl with the new strand to the 5’ phosphate of the previous fragment with a phosphodiester bond

• structural differences of purine/ pyrimidines • proof reading activity of DNA polymerase • mismatch repair

making RNA from DNA - uses RNA polymerase II complex and helicase to unwind DNA duplex to form a transcription bubble

• protiens that turn on or off binding to nearby DNA • binding sites called enhancers of silencers

• transcription factor II D binds to the TATA box which allows adjacent binding of transcription factor II B • TFIID causes distortion of the DNA at the TATA box • other transcription factors bind along with RNA polymerase II forming a transcription initiation complex • TFIIH - parts double helix at the transcription start point, exposing template strand

• physically links the transcription factors to other components of the initiation complex to RNA polymerase II • allows activator protein to communicate with RNA polymerase II

• 5’ end of pre-mRNA is modifies to form a cap • 3’ end is adenylated

• splice donor • splice acceptor • branch site

• cut at the splice donor site at the 5’ end of the intron • cut at the splice acceptor site at the 3’ end of the intron • this is catalysed by spliceosomes • matured RNA is then exported from the nucleus into the cytosol and guided through nuclear pore complex

• mRNA is translated through complementary codon on a tRNA molecule • 4 short sections of tRNA, are double helical • an anticodon binds to the complementary codon on the mRNA molecule • there is a short single stranded region at the 3’ end where there is an amino acid attachment site

• A site (accepting) • P site (processing) • E site (exciting)

• the 2 subunits of ribosomes join together at the 5; end of the tRNA transcript • mRNA is pulled through the ribosome 3 nucleotides at a time • codons enter ribosome core the mRNA sequence is translated to amino acids

• tRNA binding • peptide bond formation • large subunit translocation • small subunit translocation

• make translation more efficient and accurate • enter and leave ribosome during each facto • hydrolyse GTP and GDP • ensure translation occurs forwards

• induce fit • kinetic proofreading

• start codon and initiator tRNA are recognised by specific initiator factors due to the unique nucleotide sequence • loaded into the small subunit with eukaryotic initiation factors • initiator factors bind to the p site • small subunit binds to 5’ end of the mRNA and is recognised by the cap • move 5’ to 3’ to find start codon 5 when found initiation factors dissociate and allow binding of the large subunit to allow protein synthesis and translation