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

Remember Proteins?? Proteins are the most versatile macromolecules in living systems and serve crucial functions in essentially all biological processes such as: Function as catalysts Transport and store other molecules such as oxygen Provide mechanical support and immune protection Generate movement Transmit nerve impulses Control growth and differentiation. #proteinsmatter

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

(Remember: RNA has uracil instead of thymine, so A binds with U) TRANSCRIPTION Process: RNA Polymerase binds to the DNA promoter where transcription is to begin and unzips the gene that needs to be copied. (looks for “TATA box” as a signal) RNA Polymerase uses 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 DNA zips back up and the mRNA leave the nucleus and enters the cytoplasm

Transcription: DNA is copied into a complementary strand of mRNA RNA is made in the 5’-3’ direction The DNA template read in the 3’-5’ direction 3’ 5’ 3’ 5’ 5’ 3’ 5’ 3’ 3’ 5’ DNA mRNA DNA mRNA DNA

Transcription – Try it! 3’ TACGCTAGTACGATT 5’ 5’ AUGCGAUCAUGCUAA 3’ DNA sequence (template): 3’ TACGCTAGTACGATT 5’ mRNA sequence: 5’ AUGCGAUCAUGCUAA 3’

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)

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

TRANSLATION Process: mRNA attaches to the small subunit of the ribosome Ribosome reads the mRNA codons (3 mRNA nucleotides – like a triplet) ALWAYS in the 5’ to 3’ direction; starting at codon AUG. tRNA (transfer RNA) molecules act like taxis to pick up and drop off the amino acids that match with the current codon being read off the mRNA. 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.

The Genetic Code Resources I love: Protein Synthesis Interactive: http://learn.genetics.utah.edu/content/basics/transcribe/ Translation Animation: http://www.youtube.com/watch?v=NJxobgkPEAo

Transcription and Translation: Try it! DNA sequence (template): 3’ TACGCTAGTACGATT 5’ mRNA sequence: 5’ AUGCGAUCAUGCUAA 3’ Codons: AUG CGA UCA UGC UAA Amino Acids: Met – Arg – Ser – Cys – stop