RNA and Protein Synthesis: The Human Code

1. CHAPTER 13 RNA and Protein Synthesis Protein Synthesis 2:30

2. The Human Code • The human genome contains approximately 3 billion base pairs which reside in the 23 pairs of chromosomes within the nucleus of all our cells. • Each of the estimated 30,000 genes in the human genome makes an average of three proteins. • Humans share • 99.9% of DNA with each other (We only differ by .1% genetically!!!!) • 98.4% of DNA with Chimpanzees • 50% of DNA with Bananas

3. Chapter 13 Questions: Part 1 • In your notes answer the following questions as we go through the presentation. • *Use complete sentences and write legibly • What is the role of RNA? Explain in relationship to DNA. • Explain the function of ribosomes. • Describe how mRNA, rRNA, and tRNA work together to produce functional proteins.

4. Differences between DNA and RNA DNA RNA • Sugar = Deoxyribose • Double stranded • Bases • Cytosine • Guanine • Adenine • Thymine • Sugar = Ribose • Single Stranded • Bases • Cytosine • Guanine • Adenine • URACIL (U) These chemical differences make it easy for the enzymes in the cell to tell DNA and RNA apart

5. What is RNA? • Remember that DNA carries the genetic information in cells • RNA - a single-stranded nucleic acid that contains ribose as its sugar • RNA is involved in using DNA to code for Proteins • The instructions from DNA are copied as RNA. RNA can be used to make proteins

6. The role of DNA and RNA in the cell • The roles played by DNA and RNA are similar to the master plans and blueprints used by builders. • DNA = The master plan: has all the information needed to construct a building. Builders never bring a valuable master plan to the building site!!!!! • RNA = Blueprint: Inexpensive, disposable copies of the master plan called blueprints.

7. The 3 main types of RNA • Messenger RNA (mRNA) • Carries a copy of the instructions from the nucleus to the cytoplasm where it meets up with a ribosome to make a protein. • Ribosomal RNA (rRNA) • Makes up the structure of ribosomes • Transfer RNA (tRNA) • Transfers amino acids to the ribosomes to match them with the coded mRNA message.

8. A 4th type of RNA (not in you book) • Small nuclear RNA (snRNA) • Edits the mRNA before it leaves the nucleus

9. How is RNA made? • Transcription = DNA segments serve as templates to produce complementary RNA molecules (mRNA) • In eukaryotes transcription takes place in the nucleus • mRNA is the disposable copy of the DNA instructions • Many mRNA molecules can be made from one gene

10. The role of RNA polymerase • RNA polymerase = an enzyme that binds to DNA • 1) Separates the DNA strand • 2) Uses one DNA strand as a template to create an RNA molecule • Promoter = region of DNA with specific base sequences that signal the RNA polymerase where to start making RNA • mRNA is edited before it leaves the nucleus • Introns = regions that are cut out • Exons = regions that form the final RNA

11. Chapter 13 Questions: Part 1 • Answers • What is the role of RNA? Explain in relationship to DNA. • The role of RNA is to transmit coded information found in DNA and create proteins. RNA is created from base pair sequencing found in DNA whereby all nitrogenous bases are paired up and Uracil replaces Thymine. • 2. Explain the function of ribosomes. • Ribosomes are responsible for creating polypeptide chains of amino acids which will result in the creation of new proteins. • 3. Describe how mRNA, rRNA, and tRNA work together to produce functional proteins. • Messanger RNA (mRNA) carries a coded message from DNA to the ribosome which is synthesized from ribosomal RNA (rRNA). From this point transfer RNA (tRNA) uses base pairing rules to bring amino acids to the ribosome for protein synthesis.

12. Chapter 13 Questions: Part 2 • In your notes answer the following questions: • 4. What are codons and what do they code for? • 5. Define translation. • 6. Explain the role of tRNA and “stop” codons to produce polypeptide chains, which ultimately form new proteins.

13. The Genetic Code • The bases in DNA and RNA - A, C, G, T (U) code for making proteins • The 4 bases code for 20 different amino acids (proteins) • The genetic code is read three “letters” at a time, so that each “word” is three bases long and corresponds to a single amino acid • These amino acids can be combined into long chains = polypeptides • The sequence of amino acids determines the structure of the protein

14. Codon • Codon = each three-letter “word” in mRNA • consists of three consecutive bases that specify a single amino acid to be added to the polypeptide chain

15. The Genetic Code • There are 64 possible three-base codons (4 × 4 × 4 = 64) in the genetic code. • To read a codon, start at the middle of the circle and move outward. • GAG = Glutamic Acid • CGU = Arginine • Start codon = AUG = methionine • Stop codon = UGA, UAA, UAG

16. Translation • Translation = the decoding of an mRNA message into a protein. • Ribosomes use the sequence of codons in mRNA to assemble amino acids into polypeptide chains

17. tRNA • Each tRNA molecule carries just one kind of amino acid. • Anticodon = three unpaired bases—which is complementary to one mRNA codon.

18. The process of translation 1) A ribosome attaches to a mRNA molecule in the cytoplasm. 2) As the ribosome reads each codon of mRNA, it directs tRNA to bring the specified amino acid into the ribosome. 3) One at a time, the ribosome then attaches each amino acid to the growing chain and breaks the bond between the tRNA and amino acid

19. Translation 4) The tRNA moves into a third binding site, from which it exits the ribosome. 5) The ribosome moves to the third codon, where tRNA brings it the amino acid specified by the third codon.

20. Translation 6) The polypeptide chain continues to grow until the ribosome reaches a “stop” codon on the mRNA molecule. 7) When the ribosome reaches a stop codon, it releases both the newly formed polypeptide and the mRNA molecule, completing the process of translation.

21. Chapter 13 Questions: Part 2 • Answers • 4. What are codons and what do they code for? • A codon consists of three consecutive bases that specify a single amino acid to be added to the polypeptide chain and ultimately produce a protein. • 5. Define translation. • Translation is the decoding of an mRNA message into a protein. • 6. Explain the role of tRNA and “stop” codons to produce polypeptide chains, which ultimately form new proteins. • tRNA is responsible for transporting amino acids to the ribosome for protein synthesis. A “stop” codon signals that a polypeptide chain is complete.

22. transcription and translation protein folding

23. Central Dogma • Information is transferred from DNA to RNA to PROTEIN • Exceptions include retroviruses (ex HIV) where information is moved from RNA to DNA • Gene expression - the way in which DNA, RNA, and proteins are involved in putting genetic information into action in living cells.

25. The Genetic Code • The genetic code is near-universal • Some organisms show slight variations in the amino acids assigned to particular codons • But the code is always read three bases at a time and in the same direction.

26. Mutations • Mutations = heritable changes in genetic information • Two categories of mutations 1) Gene mutations = mutations that produce changes in a single gene 2) Chromosomal mutations = mutations that produce changes in whole chromosomes

27. Gene Mutations • Point mutations = mutations that involve changes in one or a few nucleotides • Occur at a single point in the DNA sequence • Usually occur during replication. • If a gene in one cell is altered, the alteration can be passed on to every cell that develops from the original one.

28. Types of Gene Mutations • Substitution - one base is changed to a different base • May change one amino acid • Insertion – one base is inserted • Deletion – one base is deleted • Insertion and deletions are frameshift mutations – they shift the reading frame of the message and change multiple amino acids

29. Sickle Cell Mutations • The sickle cell mutation is a point mutation that affects the hemoglobin in red blood cells. • A single base change from and adenine to uracil changes glutamic acid to valine

30. Sickle Cell Mutations • This mutation however seems to “help” populations where malaria is endemic. (e.g. certain parts of Africa)….. Why? • Malaria affects 400 million people annually and kills 2-3 million • People with the sickle cell trait are more likely to survive acute malaria illness

31. Sickle Cell Mutations • Red cells affected with malaria become deformed. • People with the sickle cell trait remove those cells more affectively which reduce the parasite burden in people

32. Chromosomal Mutations • Deletion – involves the loss of part of a chromosome • Duplication – involves an extra copy of part or all of the chromosome • Inversion – reverses the direction of part of the chromosome • Translocation – when part of one chromosome breaks off and attaches to another

33. Chapter 13 Questions: Part 3 • On a separate (clean – no rough edges) piece of paper answer the following questions: • *Use complete sentences and write legibly • Turn in Chapter 13 Questions from this presentation when you are finished. • 7. Use a dictionary and define Dogma. • 8. Explain the central dogma of gene expression as it relates to DNA, RNA, and Protein. • 9. Define gene expression, and explain why the Genetic Code can be described as “near-universal”.

34. Chapter 13 Questions: Part 3 • Answers • 7. Use a dictionary and define Dogma. • A principle or set of principles laid down by an authority as incontrovertibly true. • 8. Explain the central dogma of gene expression as it relates to DNA, RNA, and Protein. • In all living systems information is transferred from DNA to RNA to PROTEIN. • 9. Define gene expression, and explain why the Genetic Code can be described as “near-universal”. • Gene expression is the way in which DNA, RNA, and proteins are involved in putting genetic information into action in living cells. It can be considered “near universal” because it applies to nearly all living things.

35. Chapter 13 Extra Credit • On a separate (clean – no rough edges) piece of paper answer the following questions: • *Use complete sentences and write legibly • Worth the read! • And a good opportunity for 15 extra credit points! • Go to • http://www.naturalhistorymag.com/samplings/033426/portrait-of-a-protein • Read this short article and summarize how the researchers are able to look at proteins and how these images will benefit medical science. • Due Monday for credit