Central Dogma of Genetics Protein Synthesis The process of reading the instructions in the DNA to make a protein. Central Dogma of Genetics DNA = instructions and is in the nucleus and can’t leave But proteins are made in ribosomes So protein synthesis takes 2 steps: transcription translation DNA RNA protein

DNA TRANSCRIPTION RNA TRANSLATION Protein

Three Essential Types of RNA mRNA (messenger): copies instructions in DNA and carries these to the ribosomes in the cytoplasm tRNA (transfer): carries amino acids to the ribosome and mRNA rRNA (ribosomal): composes the ribosome

TRANSCRIPTION Purpose: Carry the code/instructions out of the nucleus (Remember: DNA never leaves the nucleus, and proteins are made in the cytoplasm by ribosomes.) Location: Nucleus Starts with: DNA Ends with: mRNA

Transciption

TRANSCRIPTION Process: Unzip the gene that needs to be copied Use complementary base-pairing rules to match RNA nucleotides with the exposed DNA nucleotides (Remember: RNA has uracil instead of thymine, so A binds with U)

Release the completed mRNA molecule (mRNA = messenger RNA) DNA zips back up and the mRNA leave the nucleus and enters the cytoplasm

Transcription: DNA is copied into a complementary strand of mRNA

Transcription – Try it! TAC GCT AGT ACG ATT AUG CGA UCA UGC UAA DNA sequence (template): TAC GCT AGT ACG ATT mRNA sequence: AUG CGA UCA UGC UAA

Translation Vocabulary Genetic Code: code of instructions for how to make proteins Codon: a set of 3 nucleotides on the mRNA mRNA (messenger) Amino acid –monomer (building block) for making proteins, held together by peptide bonds Anticodon: “complementary” 3 nucleotides on tRNA tRNA (transfer)

AMINO ACIDS  POLYPEPTIDE  PROTEIN

TRANSLATION Purpose: Read/follow the instructions carried on the mRNA to make a protein Location: In the Cytoplasm at the Ribosome Starts with: mRNA Ends with: Protein

TRANSLATION Process: mRNA attaches to a ribosome. Ribosome reads the mRNA codons (3 RNA nucleotides – like a triplet.)

tRNA (transfer RNA) molecules act like taxis to pick up and drop off the amino acids that match with the current codon. tRNA’s continue to drop off amino acids, and the ribosome binds the amino acids together with peptide bonds. When the “stop codon” is reached, the ribosome releases the completed protein.

Translation: interpreting the RNA message into a protein.

EACH tRNA carries only one kind of amino acid ANTICODON on tRNA matches up with CODON on mRNA

The Genetic Code The “words” of the DNA “language” are triplets of bases called codons The codons in a gene specify the amino acid sequence of a polypeptide there are 64 different codons but only 20 amino acids (some amino acids have more than one codon) AUG is the “start codon” UGA, UAA, UAG are all “stop codons”

The Genetic Code

Transcription and Translation: Try it! DNA sequence (template): TACGCTAGTACGATT mRNA sequence: AUGCGAUCAUGCUAA Codons: AUG CGA UCA UGC UAA Amino Acids: Met – Arg – Ser – Cys – stop Resources I love: Translation Animation: http://www.cmbi.ru.nl/edu/VWO/4vwodag/gene3.swf Protein Synthesis Interactive: http://learn.genetics.utah.edu/content/basics/transcribe/ Translation Animation: http://www.youtube.com/watch?v=NJxobgkPEAo