PROTEIN SYNTHESIS: Transcription & Translation

1. PROTEIN SYNTHESIS:Transcription & Translation

2. Protein Synthesis Videos • http://www.youtube.com/watch?v=41_Ne5mS2ls • http://www.youtube.com/watch?v=983lhh20rGY&feature=related

3. I. What are Proteins? • Proteins are organic molecules made of various arrangements of 20 amino acids • Examples- 1. Enzymes. 2. Transport proteins and receptor molecules in cell membranes -ex. hemoglobin

4. … I. What are Proteins? (con’t) • Hormones- ex. Insulin, adrenaline, testosterone • Structural proteins- ex. Keratin and collagen in skin, actin and myosin of muscle.

5. … I. What are Proteins? (con’t) • Antibodies • Storage molecules- ex. Albumin in egg white, casein in milk, and plant proteins in seeds.

6. REVIEW… AGAIN • Chromosomes are made of DNA • Segments of DNA code for a protein (Genes) • Protein in turn, relates to a trait (eye color, enzymes, hormones..)

7. C. Shape of DNA-twisted ladder S • Sides of the ladder= sugar + phosphate • Rungs (steps) = nitrogen bases S NB P P S S NB P P NB S S

8. Shape of DNA-twisted ladder(con’t) S 3. sugar + phosphate are held together by strongcovalent bonds 4. nitrogen bases are held together by weakhydrogen bonds S NB P P S S NB P P NB S S

9. DNA REPLICATION • Replication is the process where DNA makes a copy of itself. • DNA are instructions to know how to be a cell. • DNA replicates right before a cell divides. (In Interphase of Cell Cycle)

10. E. DNA’s Problem • DNA cannot leave the nucleus. • So, How does it get the instructions to the ribosome?.... … RNA

11. RNA = ribonucleic acid • RNA is similar to DNA except: 1. Single stranded2. Uracil instead of thymine3. Riboseinstead of deoxyribose • mRNA has the job of taking the message from the DNA in the nucleus to the ribosomes. • Transcription – (in Nucleus) • RNA is made from DNA’s code(message) • Translation – (on Ribosome) • Proteins are made from the message on the RNA

12. B. Types of RNA • mRNA- messenger RNA takes DNA’s instruction from the nucleus to the ribosome. • tRNA- transfer RNA brings an amino acid from the cytoplasm to the ribosome. • rRNA- ribosomal RNA

13. DNA Transcription Ribosome mRNA Translation Polypeptide (protein) The Central Dogma: Proteins can’t be made back into Nucleic Acids. Cell

14. Transcription: Protein Synthesis Transcription is the process by which a molecule of DNA is copied into a complementary strand of RNA. This is called messenger RNA (mRNA) because it acts as a messenger between DNA and the ribosomes where protein synthesis is carried out. DNA RNA Proteins Transcription Translation HAPPENING IN NUCLEUS HAPPENING IN CYTOPLASM ON RIBOSOME

15. Transcription • DNA Strand: T G C A T C A G A • RNA Strand: A C G U A G U C U • DNA is transcribed into mRNA (messenger RNA) • mRNA leaves the nucleus and travels to the cytoplasm to find a Ribosome! • In order to use DNA’a message to make a protein for the body

16. Transcription process RNA polymerase (an enzyme) attaches to DNA at a special sequence that serves as a“start signal”. The DNA strands are separated at the H-bonds and Nitrogen bases and one strandserves as a template. The RNA bases attach to the complementary DNA template, thus synthesizing (making) mRNA.

17. Transcription process continued The RNA polymerase recognizes a termination site on the DNA molecule and releases the new mRNA molecule. (mRNA leaves the nucleus and travels to the ribosome in the cytoplasm.)

18. deoxyribose ribose phosphate uracil adenine B. Steps of Transcription: thymine cytosine guanine DNA strand 1. The DNA strands separate at the H-bonds holding the nitrogen bases together. *An enzyme causes the unwinding. The Nucleus

19. deoxyribose ribose phosphate uracil adenine B. Steps of Transcription: thymine cytosine guanine DNA strand 2. mRNA (messenger RNA) nucleotides in the nucleoplasm then base-pair with the DNA. Another enzyme catalyzes this. The Nucleus

20. deoxyribose ribose phosphate uracil adenine B. Steps of Transcription: thymine cytosine guanine DNA strand 3. The mRNA nucleotides covalently bond to each other between sugars and phosphates. The Nucleus

21. deoxyribose ribose phosphate uracil adenine B. Steps of Transcription: thymine cytosine guanine DNA strand 4. The DNA strands will bond back together. 5. The mRNA chain can now leave the nucleus. The Nucleus

22. deoxyribose ribose phosphate uracil adenine B. Steps of Transcription: thymine cytosine guanine DNA strand 6. Where is mRNA going? ………………………………to a ribosome The Nucleus

23. Protein Synthesis: Transcription

24. Transcription

25. Protein Synthesis: Translation Translationis the process of decoding a mRNA molecule’s message from DNA into apolypeptide chain orprotein. Each combination of 3 nucleotides on mRNA is called a codon. Each codon specifies a particular amino acid that is to be placed in the amino acid chain which makes a protein. Ribosomes in the cytoplasm use the code on mRNA to translate it into amino acids

26. How the code is read: • Every 3 bases on mRNA represents a code for an amino acid (building block of protein) • Every 3 bases on mRNA is called a codon. • Amino acids are abbreviated most times by using the first 3 letters of the amino acid’s name. • Met = methonine • Leu = leucine

27. Reading the Codon Chart Slide # 10 Examples: AUG = Methionine CAU = Histidine UAG = Stop Third Position First Position Try these: GCU: UAC: CUG: UUA: Answers: Alanine Tyrosine Leucine Leucine This chart only works for mRNA codons.

28. Translation of mRNA

29. Protein Synthesis: Translation Transfer RNA (tRNA) Each tRNA molecule has 2 important sites of attachment. One site, called the anticodon, binds to the codon on the mRNA molecule. The other site attaches to a particular aminoacid. During protein synthesis, the anticodon of a tRNA molecule base pairs with the appropriate mRNA codon.

30. Protein Synthesis: Translation The protein chain (amino acids) continues to grow. Until a stop codon reaches the ribosome Which results in the release of the new protein and mRNA, completing the process of translation. Amino acids form a chain = a protein

31. STEPS OF TRANSLATION 1. The mRNA travels to the cytoplasm2. Amino acids exist freely in the cytoplasm, many of them you acquire from your diet3. Each 3 bases of mRNA (codon) translates (has a message to make a single amino acid.) 4. The ribosome looks for the "start" codon - AUG, this is where the chain begins5. Transfer (tRNA), has an anticodon at one end and an amino acid at the other, it binds to a complementary codon.

32. 6. Another tRNA reads the next codon, the amino acid attached to it binds with the amino acid on the previous tRNA using a peptide bond. The first tRNA falls off.7. This process continues until the "stop" codon is reached.8. The amino acid chainfolds into a 3 dimensional structure, now a protein.9. That protein can be an enzyme, a hormone, or any other structure in the body that gives it traits and functionality.

33.  Translation Slide # 12 Nucleus mRNA  Lysine Phenylalanine t RNA Methionine  Anticodon Ribosome mRNA  Start codon Go to Section:

34. Translation Slide # 13 Growing polypeptide chain The Polypeptide “Assembly Line” Ribosome tRNA Lysine tRNA mRNA Completing the Polypeptide mRNA Translation direction Ribosome Go to Section:

35. nucleus U mRNA C C C A U A U U G U G A mRNA codon codon codon codon cytoplasm ribosome

36. nucleus tRNA anticodon A G A U C mRNA C C C A U A U U G U G A mRNA codon codon codon codon START cytoplasm ribosome

37. proline START nucleus tRNA tRNA anticodon A G G mRNA C C C A U A U U G U G A mRNA codon codon codon codon cytoplasm ribosome

38. valine proline START nucleus tRNA anticodon U A C mRNA C C C A U A U U G U G A mRNA codon codon codon codon cytoplasm ribosome

39. leucine valine proline START nucleus tRNA anticodon anticodon A A G U mRNA C C C A U A U U G U G A mRNA codon codon codon codon cytoplasm ribosome cytoplasm

40. Translation

42. DNA TRANSLATIONtRNA translates mRNA into proteins

43. SUMMARY

45. Mutation • Any mistake or change in DNA sequence • TYPES: • SubstitutionA substitution is a mutation that exchanges one base for another (i.e., a change in a single "chemical letter" such as switching an A to a G).

46. InsertionInsertions are mutations in which extra base pairs are inserted into a new place in the DNA. • DeletionDeletions are mutations in which a section of DNA is lost, or deleted

47. Frameshift • Since protein-coding DNA is divided into codons three bases long, insertions and deletions can alter a gene so that its message is no longer correctly parsed. • These changes are called frameshifts. For example, consider the sentence, "The fat cat sat." Each word represents a codon. If we delete the first letter and parse the sentence in the same way, it doesn't make sense.

48. Mutagen • Any agent capable of altering a cell’s genetic makeup (DNA); causes a mutation • Examples: • Cosmic rays • X-rays • UV light • Some chemicals

49. Mutations and Genetic Disorders

50. Introduction to Mutations Slide # 2 • Most genetic disorders result from a mutation in one gene. • Mutation: a change in an organism’s genetic material (DNA) • A mutated gene produces a flawed protein that does not function properly or a protein that does not function at all. • Examples of genetic disorders that are caused by the mutation of one gene: Hemophilia, sickle cellanemia, and cystic fibrosis. Normal blood cells Sickle-shaped blood cells