2. Protein Synthesis 1

3. Background Information All information is stored in DNA All information is stored in DNA RNA “reads” the DNA code RNA “reads” the DNA code DNA is found in base triplets (sets of three letters) DNA is found in base triplets (sets of three letters) Complimentary sequence of RNA (after reading DNA) will be called a codon Complimentary sequence of RNA (after reading DNA) will be called a codon Done in the cell Nucleus Done in the cell Nucleus 2

4. Transcription In this phase the genetic information represented by the sequence of each DNA base triplet serves as a template for copying the information into a complimentary sequence of RNA In this phase the genetic information represented by the sequence of each DNA base triplet serves as a template for copying the information into a complimentary sequence of RNA Three kinds of RNA will be made from the DNA template Three kinds of RNA will be made from the DNA template 1. Messenger RNA (mRNA) directs protein synthesis 2. Ribosomal RNA (rRNA) joins with ribosomal proteins to make ribosomes 3. Transfer RNA (tRNA) binds to an amino acid and holds it in place on a ribosome until it is incorporated into a protein during translation 3

5. Transcription Cont. The process is catalyzed by the enzyme RNA polymerase The process is catalyzed by the enzyme RNA polymerase This enzyme needs to be told where to begin and where to end This enzyme needs to be told where to begin and where to end The PROMOTER is the nucleotide sequence of DNA that instructs RNA polymerase where to begin. The PROMOTER is the nucleotide sequence of DNA that instructs RNA polymerase where to begin. During the transcription process the bases are paired up in a complimentary manner During the transcription process the bases are paired up in a complimentary manner 4

6. Cont. The bases C, G, and T from DNA pair up with G, C, and A in the RNA. The bases C, G, and T from DNA pair up with G, C, and A in the RNA. However, adenine in the DNA template pairs up with U (uracil) and not thymine in the RNA sequence However, adenine in the DNA template pairs up with U (uracil) and not thymine in the RNA sequence So, DNA (CGA) reads (GCU) in RNA. So, DNA (CGA) reads (GCU) in RNA. Transcription continues until the terminator sequence is read Transcription continues until the terminator sequence is read Once this happens RNA Polymerase detaches and the process ends. Once this happens RNA Polymerase detaches and the process ends. 5

7. 6

8. 7

9. Translation Process where the nucleotide sequence in an mRNA molecule specifies the amino acid sequence of a protein Process where the nucleotide sequence in an mRNA molecule specifies the amino acid sequence of a protein Occurs on a ribosome in the cytosol Occurs on a ribosome in the cytosol 8

10. Stages of Translation mRNA binds to the small part of a ribosome at the mRNA binding site mRNA binds to the small part of a ribosome at the mRNA binding site Initiator tRNA binds to the start codon (AUG) on mRNA. Initiator tRNA binds to the start codon (AUG) on mRNA. The tRNA anticodon (UAG) attaches to the mRNA codon (AUG) by pairing between the complementary bases The tRNA anticodon (UAG) attaches to the mRNA codon (AUG) by pairing between the complementary bases AUG is the start codon, and it is the codon for methionine, which means that methionine is always the first amino acid in the protein building process AUG is the start codon, and it is the codon for methionine, which means that methionine is always the first amino acid in the protein building process 9

11. Stages Cont. From this point, the ribosome will continue to add amino acids in the sequence that is given to it by the mRNA strand. From this point, the ribosome will continue to add amino acids in the sequence that is given to it by the mRNA strand. The ribosome reads the remainder of the strand one codon at a time, and from here the protein lengthens The ribosome reads the remainder of the strand one codon at a time, and from here the protein lengthens The process moves in what we call a 3’ to 5’ direction The process moves in what we call a 3’ to 5’ direction The process ends when a stop codon is read, which leads to the detachment of the protein from the final tRNA. The process ends when a stop codon is read, which leads to the detachment of the protein from the final tRNA. 10

12. Final Translation Facts Occurs at about a 15 peptide bond per second rate Occurs at about a 15 peptide bond per second rate As one ribosome finishes with a strand of mRNA, another one usually picks it up and translates it, so that more than one copy of protein can be made As one ribosome finishes with a strand of mRNA, another one usually picks it up and translates it, so that more than one copy of protein can be made Process constantly occurs. Process constantly occurs. 11

13. 12

14. 13

15. 14

16. 15

17. 16

18. 17

19. 18

20. 19