RNA and Protein Synthesis

Gene Segment of DNA that specifies the sequence of amino acids in protein

RNA structure 3. Uracil replaces thymine 2. Ribose replaces deoxyribose 1. Single stranded Uracil instead of thymine

Main function of RNA Protein synthesis Amino acid sequence 20 different amino acids

journal Information, Please DNA contains the information that a cell needs to carry out all of its functions. In a way, DNA is like the cell’s encyclopedia. Suppose that you go to the library to do research for a science project. You find the information in an encyclopedia. You go to the desk to sign out the book, but the librarian informs you that this book is for reference only and may not be taken out. 1.Why do you think the library holds some books for reference only? 2.If you can’t borrow a book, how can you take home the information in it? 3. All of the parts of a cell are controlled by the information in DNA, yet DNA does not leave the nucleus. How do you think the information in DNA might get from the nucleus to the rest of the cell?

Location of protein synthesis ribosomes

3 types of RNA Messenger RNA (mRNA) – Takes message from DNA in nucleus to ribosomes in cytoplasm Contains codons DNA strand: A T C G A T C T T A A T C m RNA strand : U A G C U A G codon codon Ribosomal RNA (rRNA) – Found in ribosomes along with other proteins Transfer RNA (tRNA) – Transfers each amino acid to the ribosome Contains anitcodons (complementary to codon)

Protein synthesis happens in 2 steps: 1.Transcription: RNA copies DNA sequence (but U for T) RNA polymerase Separates DNA and builds complementary RNA strand Occurs in nucleus, then edited and mRNA copy moves to cytoplasm Promoter Tell mRNA where gene starts 2. Translation: mRNA directs sequence of amino acids - Assembles protein based on info from mRNA - tRNA brings specific amino acids to chain - anticodon of the tRNA complements the codon of the mRNA

RNA DNA RNA polymerase Messenger RNA TRANSCRIPTION

mRNA has to be edited before leaves nucleus introns get removed Introns don’t code for proteins - so removed Exons - do code for proteins

“Genetic Code” is on mRNA Instructs sequence of amino acids AUCG :letters make up code Triplet code: 3 nucleotide bases = one codon -Each codon encodes for one amino acid (except “stop” codons) -There are codons for all 20 different amino acids

Translation Start codon AUG Stop codons UGA, UAA, UAG anticodon

Chapter 12

fromtoto make up also calledwhich functions toalso called which functions to can be RNA Messenger RNA Ribosomal RNA Transfer RNA mRNACarry instructions rRNA Combine with proteins tRNA Bring amino acids to ribosome DNARibosomeRibosomes

Regulation of Protein Synthesis Every cell in your body, with the exception of gametes, or sex cells, contains a complete copy of your DNA. Why, then, are some cells nerve cells with dendrites and axons, while others are red blood cells that have lost their nuclei and are packed with hemoglobin? Why are cells so different in structure and function? If the characteristics of a cell depend upon the proteins that are synthesized, what does this tell you about protein synthesis? Work with a partner to discuss and answer the questions that follow. 1.Do you think that cells produce all the proteins for which the DNA (genes) code? Why or why not? How do the proteins made affect the type and function of cells?

Practice on board Practice on board: Then complete HW

Mutations start here

What can mutations do to amino acid sequence? 1.Copy the following information about Protein X: Methionine— Phenylalanine—Tryptophan—Asparagine—Isoleucine—STOP. 2.Use Figure 12–17 on page 303 in your textbook to determine one possible sequence of RNA to code for this information. Write this code below the description of Protein X. Below this, write the DNA code that would produce this RNA sequence. 3.Now, cause a mutation in the gene sequence that you just determined by deleting the fourth base in the DNA sequence. Write this new sequence. 4.Write the new RNA sequence that would be produced. Below that, write the amino acid sequence that would result from this mutation in your gene. Call this Protein Y. 5.Did this single deletion cause much change in your protein? Explain your answer.

Substitution Insertion Deletion

Duplication Inversion Translocation