Do Now: Imagine you have an original Michaelangelo painting Do Now: Imagine you have an original Michaelangelo painting. What would you do with it? How would you prevent it from getting damaged? Why are we talking about paintings at all???

DNA Transcription and Translation

What is the major job of DNA? How does it do that job? Form proteins Store instructions in DNA Copy instructions to more DNA or RNA Transmit by translating instructions to amino acid (aa) chain

Do DNA and RNA look the same? Several types Single stranded Ribose Sugar A, C, G, U Can leave nucleus DNA Double stranded Deoxyribose Sugar A, C, G, T Isolated in nucleus

~ 3 Types of RNA ~ mRNA (messenger) – carry DNA info to cytoplasm rRNA (ribosomal) – attach to mRNA, use info to assemble aa’s in correct order tRNA (transfer) – transports aa’s to ribosome to assemble proteins

How do we get from DNA to RNA??? Transcription!!! Process of getting info in DNA out of nucleus to cytoplasm RNA copy made in nucleus mRNA carries info

Steps of Transcription Enzyme helicase unzips DNA

RNA polymerase pairs RNA nucleotides with complementary bases on DNA template strand (U’s instead of T’s)

Completed mRNA strand breaks away DNA rezips Mature mRNA has a cap and tail (protects); all unused parts of message are edited out mRNA leaves through nuclear pore mRNA enters cytoplasm Who will mRNA meet?

How do we now get to protein assembly??? TransLATION!!! Transcribe vs. Translate *Rewriting in *Converting one different form language into (language) another

A little about protein language… What are the building blocks of proteins? AMINO ACIDS!! Remember: 20 different amino acids aa’s coded for by THREE nucleotides –codons 4 bases, 3 per codon: 43 = 64 total possible combinations

Why don’t these numbers match? 20 amino acids, 64 options?? WOBBLE In case of mistakes in DNA, close combinations can result in replacement of same amino acid

Do all organisms have same code? Why or why not??? ALL organisms share same code Most codons code for amino acids START codon (AUG) - Methionine STOP codons (UGA, UAA, UAG) – end protein production

Review repeats in the code, start codon, & stop codons

Steps of Translation Ribosomes (rRNA) attach to mRNA carries code  tRNA’s carry amino acid and have anticodon complementary to mRNA

Protein production starts when START (AUG) is coded for

Ribosome slides along mRNA in 3’s (in frame) and tRNA brings matching aa’s

aa’s joined by dehydration synthesis to form peptide bond; tRNA released

Process continues until STOP codon is reached

** Central idea of cellular and molecular biology ** Gene Expression ** Central idea of cellular and molecular biology ** DNA → RNA → amino acid → protein chain

Interactive Gene Expression Activity