Transcription & Translation  If I have a DNA sequence of AAG CTC ATA What will my mRNA sequence be?  What will the tRNA sequence from that mRNA sequence be?

Transcription & Translation 1.Fill in the blanks: ____ -> _____ -> ________ -> _______ 1.What is the sequence of the RNA molecule that you get from this strand of DNA? AATGCG 2.What do you call that kind of RNA? 3.Was that the template strand or the gene strand of DNA? 1.Fill in the blanks: ____ -> _____ -> ________ -> _______ 1.What is the sequence of the RNA molecule that you get from this strand of DNA? AATGCG 2.What do you call that kind of RNA? 3.Was that the template strand or the gene strand of DNA?

Homework

Review Transcription  Turn to your table partner and explain how transcription works.

Review Transcription  I have a DNA strand with these sequences: CGTTCGACTGATCGT GCAAGCTGACTAGCA RNA is made by pairing with the top strand. What is the RNA sequence that results? What kind of RNA is it? What do we call the top DNA strand? The bottom DNA strand? Where in the cell did this take place?

Translation  Translation = Two parts. First, assembling a tRNA sequence from an mRNA sequence.  Once an mRNA molecule is made, it leaves the nucleus and travels through the cytoplasm to a ribosome. The rest of protein synthesis happens in the ribosome.

Translation  Two parts.  First, tRNA matches up with mRNA.  tRNA = Transfer RNA,” an RNA molecule with 3 nucleotides on one side and an amino acid on the other.  (Amino acids will be the building blocks of proteins)

Translation  Each three nucleotides on the mRNA is called a codon.  The three matching nucleotides on the tRNA is called the anticodon.

Translation  If my mRNA codon is AUG, what will be the anticodon?

Translation  If my mRNA codon is AUG, what will be the tRNA anticodon? UAC  If my mRNA codon is CCG, what will be the anticodon?

Translation  If my mRNA codon is AUG, what will be the tRNA anticodon? UAC  If my mRNA codon is CCG, what will be the anticodon? GGC  If my mRNA has the codons AUG UUA CGC GGG AAA UAA, what will be the anticodon sequence?

Translation  If my mRNA codon is AUG, what will be the tRNA anticodon? UAC  If my mRNA codon is CCG, what will be the anticodon? GGC  If my mRNA has the codons AUG UUA CGC GGG AAA UAA, what will be the anticodon sequence? UAC AAU GCG CCC UUU AUU

Translation  Second step, the amino acids that are bonded to the backs of the tRNAs bond to each other.  A chain of amino acids is called a protein. Which amino acids are in the chain, and what order they’re in, determines the type of protein.

Paper models

 class.unl.edu/biochem/gp2/m_biology/animation /gene/gene_a3.html class.unl.edu/biochem/gp2/m_biology/animation /gene/gene_a3.html  Yo Yo  s s  Y Y

Protein Synthesis = Constantly Happening

Questions I want to address…  Why all the hassle? Why coding and decoding, why RNA? Why not just make the protein from the DNA? Several reasons why it didn’t happen this way.  Amino acids can’t bond to DNA’s nucleic acids directly.  DNA is in extremely long, bunched up strands that are too big to pass through the pores in the nucleus.  The DNA is the cell’s master plan, and if it’s getting roughed up and zooming around through the cytoplasm, it’s accumulating damage. This will result in cell dysfunction and death, and the death of that strategy.

Protein Synthesis Overview  DNA -> RNA -> Protein -> Trait  TRANSCRIPTION: mRNA for a gene is made from one strand of DNA.  The mRNA leaves the nucleus and goes to the ribosome.  TRANSLATION: In the ribosome, tRNAs match up with their codons in the mRNA.  The backsides of the tRNAs have specific amino acids attached to them. When the tRNAs line up, the amino acids bond to each other and let go of the tRNA.  The chain of amino acids is called a protein.  The protein then performs a function which gives the organism a certain trait. (more on those functions next)

Protein Synthesis Overview  DNA -> RNA -> Protein -> Trait  So if I have a strand of DNA that’s like this:  TACGGGCTAACT  ATGCCCGATTGA  And my cell wants to produce the protein that’s coded for by this gene, in which the bottom strand is the gene strand.  What will be my mRNA sequence?  What will be my tRNA sequence?  What will be my amino acid sequence?  Which ones are identical to the gene strand sequence, and which ones are opposites?

Vocabulary  Protein synthesis  Genotype vs phenotype  RNA  Ribose  Uracil  mRNA  tRNA  Transcription  Translation  Codon vs Anticodon  Template strand vs gene strand  Mutation  Amino acid  Protein

Practice Problems  With your table partner, make a brief protein synthesis quiz for another pair.  One of you writes the quiz.  The other writes an answer key.  Ten problems.  Write a DNA template sequence.  The other group must figure out the codon (mRNA) and anticodon (tRNA) sequences.

Protein Synthesis  If I have a strand of DNA that is CCG ATT TAG What will the mRNA codons be?  What will the tRNA anticodons be?  How many amino acids will that make?

Homework  Quiz next week on protein synthesis.

Review  Important misconceptions:  DNA doesn’t turn into RNA. RNA is assembled by binding its nucleotides to DNA, then it pulls away.  Protein synthesis doesn’t just make “muscle proteins.” Everything the cell does to stay alive uses at least one kind of protein.  So protein synthesis is the process that ultimately determines everything that a cell does.

Review  How does transcription work?  How does translation work?  Today, a game to help you visualize transcription and translation better.