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Gene Function
3 RNA types:
mRNA - messenger; copy of DNA sequencerRNA - ribosomaltRNA - transfer; carries AA
RNA & Protein Sythesis
DNA acts as a template for the synthesis of mRNA
(process is similar to DNA replicationTranscription -
Process of making mRNARNA code has uracil in place of thymineCopy is of one gene only
Structural = encodes
for polypeptideRegulatory = control
function of other genes
Occurs in the nucleus & mRNA is able to
pass thru nuclear poresmRNA moves to ribosome site of protein synthesis
located in cytoplasm or E.R. (roug h) which is composed of rRNA and
Protein
Translation -
Converting mRNA message into an AA sequencetRNA transfers the proper AA to ribosome according
to mRNA messageSmall clover leaf structure with an mRNA "recognition"
site (anti-codo n) on one end and an AA on the other end
Codon -
Sequence of 3 nucleotides that code for 1 amino
acid1 start (methionine)3 stop (nonsense)
Protein Synthesis -
Transcription -
RNA polymerase ~> 5' to 3'Codons are unpunctuated and read in blocks
of 3 n.t. (Crick)Reading Frame - *start* to finishThe deletion of 3 n.t. did not alter the reading
frame past the deletionsmRNA breaks free of the template and moves
out of the nucleus to ribosomemRNA meets a ribosome and forms an initation
complex
Initiation Complex -
Met tRNA binds to small ribosomal subunitsInitiation factors - small proteins that position
the met tRNA (establishes the proper reading frame)Elongation factors - position tRNATerminal sequence - "stop" codonAt the end of this process, after stop codon
is reached and ribosome releases final product, you are left with
a polypeptide (protei n) 1' (straight chain)
Aminalacyl tRNA Synthesase
- binds proper AA to proper tRNA
Prokaryotic vs Eukaryotic
Prokaryotic
mRNA contains more than 1 geneWhole mRNA is translated
Eukaryotic
mRNA contains 1 gene onlyNot fully translatedIn nucleus primary mRNA transcripts sliced
Left over are ligated and become a mature
mRNAMature mRNA leaves nucleus and is translatedintrons removedexons are what is ligated togetherA lot of excessLess mutations
Chapter #16: Gene Expression
Operon - structural and regulatory genes togetherDNA - two grooves, minor
& majorGene encodes for B-galactosidase which allows lactose to be
used as an E sourceInducible gene - stimulated (induce d) to produce a
product by the presence of lactose (or another molecule)Methyl groups
(-CH3) - change protein structure a lot.
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