1. Protein Synthesis (Transcription and Translation)

2. Do You Remember? Think back to the cell analogy of a factory. Do you remember who manufactured proteins? Can you remember of what proteins are composed? Who contains the “code” to make proteins?

3. How does DNA code for proteins? The sequence of nucleotides in each gene contains information for assembling the string of amino acids that make up a single protein. The ribosomes required to make proteins cannot read DNA. Therefore, for DNA to code for proteins, an RNA molecule must be made. Ribosomes can read RNA.

4. RNA is another Nucleic Acid Nucleotide Polymer RNA differs from DNA structure in three ways. –Single stranded instead of double stranded –Ribose sugar instead of deoxyribose –Uracil instead of thymine nitrogen base Ribose sugar

5. Coding from DNA to RNA When proteins are needed to be made in the cell RNA must make a copy of the instructions for the protein from DNA Chargraff’s Rule is still used, but modified. T – A C – G, G-C A – U So wherever RNA comes across an A, a U will bind instead of a T.

6. Three types of RNA Messenger RNA (mRNA): carries the DNA code (message) to the ribosomes Ribosomal RNA (rRNA): makes up the ribosomes that reads the mRNA to build the correct amino acid sequence Transfer RNA (tRNA): brings the amino acids to the ribosome

7. Messenger RNA (mRNA) Responsible for making a copy (message) of the DNA sequence needed to make a specific protein. * This process will occur within the nucleus and the copy is then taken out of the nucleus to the cytoplasm of the cell. Code the following DNA sequence into a strand of mRNA. DNA: T A C C G G A T G C C A mRNA: A U G G C C U A C G G U

8. Ribosomal RNA (rRNA) Makes the ribosomes needed to read the mRNA message to make a protein. Remember that ribosomes are manufactured in the nucleolus of the nucleus.

9. Transfer RNA (tRNA) Responsible for bringing ribosomes the amino acids or “ingredients” needed to make the protein. tRNA must take the code read by the ribosome and bring the complimentary code of each amino acid. –Ex.mRNA:UCUGCCAAA tRNA:AGACGGUUU

10. That’s Notes for Today. Now Let’s Review and Practice.

11. Transcription The process of building an RNA strand from the DNA template Click on image to play the video. Remember A – U and C – G. In eukaryotes, this occurs inside the nucleus. In prokaryotes, this occurs in the cytoplasm.

12. mRNA processing in eukaryotes Since much of the DNA code is useless or codes for multiple proteins, the unnecessary portions of DNA that were coded into mRNA must be removed. The useless portions of RNA (introns) are removed. The coding portions (exons) are linked together to make the final mRNA.

13. mRNA codes for amino acids. Three mRNA nucleotides code for one amino acid, but more than one combination codes for the same amino acid.

14. Translation The process of ribosomes reading the mRNA code to properly make an amino acid chain that is folded into a usable protein. Bind using peptide bond.

15. Translation Initiation: The ribosome binds to AUG, the starting code (codon). The ribosome directs the methionine tRNA to bring the methionine (met) amino acid.

16. Translation * Elongation: The ribosome reads the next codon and directs the appropriate tRNA to transfer the amino acid. Bind using peptide bond.

17. Translation process Termination: The ribosome joins the amino acids together and continues this process until the codon indicates stop.

18. The End That’s all for now!!! Let’s practice

19. What happens if there is a mistake (mutation) in the DNA code? Possibly proteins won’t be made or are made improperly. If the mutations occur in the gametes, the offspring’s DNA will be affected positively, negatively, or neutrally. What can cause a mutation? –Replication error –Transcription error –Cell division error –Chemical agents (mutagens) –Spontaneous changes

20. Point mutation A point mutation is a change in a single base pair in DNA. A change in a single nitrogenous base can change the entire structure of a protein because a change in a single amino acid can affect the shape of the protein.

21. Point mutations May change the amino acid code if the mutations occurs in the right place in the code. Normal Point mutation mRNA Protein Stop mRNA Protein Replace G with A

22. Frameshift mutations Losing a single nucleotide base This mutation would cause nearly every amino acid in the protein after the deletion to be changed mRNA Protein Deletion of U

23. Changes to the chromosome When a part of a chromosome is left out, a deletion occurs When part of a chromatid breaks off and attaches to its sister chromatid, an insertion occurs. Deletion A B C D E F G H A B C E F G H Insertion A B C D E F G HA B C B C D E F G H

24. Changes to the chromosome When part of a chromosome breaks off and reattaches backwards, an inversion occurs. When part of one chromosome breaks off and is added to a different chromosome, a translocation occurs. Inversion A B C D E F G HA D C B E F G H A B E F DCBX A W C H G G E H D F W XYZYZ Translocation

25. Repairing DNA Enzymes proofread the DNA and replace incorrect nucleotides with correct nucleotides. The greater the exposure to a mutagen such as UV light, the more likely is the chance that a mistake will not be corrected.