Protein Synthesis: Part 1 (Transcription) Ch 11

Protein Synthesis means Synthesizing Proteins or “MAKING” PROTEINS

learn how proteins are made. The GOAL is to:

Protein Synthesis can be broken down into two stages: Transcription Translation

DNA mRNAProteins TRANSCRIPTIONTRANSLATION 1st PROCESS2nd PROCESS 123

Transcription Reads and copies a section of DNA (AKA gene) and converts it into mRNA (A gene codes for a protein)

Let’s compare DNA and RNA

DNARNA Sugar = deoxyribose Sugar = ribose Double helix (2 strands) Single strand

DNARNA Location: nucleus Location: Nucleus & cytoplasm Bases: A, C, G, T Bases: A, C, G, U (Uracil)

DNARNA Function: simply stores genetic info (instructions to make proteins) Function: many functions, all used to assemble proteins

Three types of RNA MESSENGER RNA (mRNA) TRANSFER RNA (tRNA) RIBOSOMAL RNA (rRNA)

MESSENGER RNA “mRNA” single strand contains genetic info is transported out of nucleus

TRANSFER RNA “tRNA” single strand folded like a hairpin binds specific amino acids

RIBOSOMAL RNA “rRNA” single strand found in ribosomes ribosomes are made up two pieces of rRNA

Let’s look at TRANSCRIPTION “The first process”

DOUBLE HELIX SPREADS APART RNA POLYMERASE copies the gene by attaching RNA nucleotides The product is called mRNA mRNA

Here the DNA is split open and a mRNA strand is being made

NOTICE: RNA POLYMERASE ADDS ON RNA NUCLEOTIDES TO MAKE mRNA

Then the newly constructed mRNA undergoes “processing” mRNA The mRNA then leaves the nucleus to enter the next process “translation” mRNA

TACTGATATCTACTGATATC DNA ATGACTATAGATGACTATAG AUGACUAUAGAUGACUAUAG RNA 3’ 5’ 3’ 5’ “start” sequence (Signals where to begin) “terminator” sequence (where to end)

RNA processing includes cutting out meaningless DNA (aka introns) Adding a cap on the tip (aka GTP cap) Adding on A-A-A-A on the end (aka Poly-A tail)

Intron + = Introns contain meaningless DNA Only the important, USEFUL DNA

Add on a GTP cap Tack on a poly-A tail mRNA GTPA-A-A You are finished processing the mRNA. It can now leave the nucleus.

Describe what is happening here and who is involved

Translation The process of converting the mRNA codons into a sequence of amino acids to build a protein. A codon is a group of three nucleotides. Each codon codes for one amino acid.

Translation – using mRNA to bring the correct tRNA anticodon, with an amino acid attached. Occurs at the ribosome..

Translation Sequence A ribosome attaches to the “start” of the mRNA. The codon “AUG” signals the start. The tRNA having the anticodon “UAC” will bring the first amino acid to the ribosome to begin the formation of the protein. The ribosome slides to the next codon on the mRNA. The complementary tRNA anticodon brings the second amino acid to the protein strand.

This process continues until the ribosome reaches a “stop” signal. Stop codons on mRNA are –UAA –UAG –UGA A Protein has been made!

Mistakes Happen – Mutations! A point mutation occurs when a single base pair is mismatched. Ex. THE DOG BIT THE CAT THE DOG BIT THE CAR A frameshift mutation occurs when a single base is added or deleted. Ex. THE DOG BIT THE CAT THE OGB ITT HEC AT (the D was deleted)

Which do you think would be more harmful? Why?