Chapter 12-3 RNA & Protein Synthesis Notes From DNA to Protein (DNA RNA Protein)

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1 Chapter 12-3 RNA & Protein Synthesis Notes From DNA to Protein (DNA RNA Protein)

2 I. Review A. Cells copy their DNA (in S phase of Interphase)-Why? Prepare for Cell Division (Mitosis & Cytokinesis)

3 Genes contain instructions for assembling 1. purines. 2. nucleosomes. 3. proteins. 4. pyrimidines. 0% 0% 0% 0% Answer Now purines. nucleosomes. proteins. pyrimidines. 20

4 B. The job of the cell is to make proteins!

5 C. The instructions are encoded in genes (DNA)

6 D. What is the process called that uses protein instructions encoded in DNA to make proteins??????? 1. Protein Synthesis!

7 II. Protein Synthesis Overview A. Occurs in 2 phases: Transcription and Translation

8 B. With the help of RNA = Ribonucleic acid 1. RNA is a disposable copy of DNA segment (coded DNA instructions that control the production of proteins within the cell) 2. A RNA molecule is a working copy of a single gene

9 3. The ability to copy a single DNA sequence into RNA makes it possible for a single gene to produce hundreds or even thousands of RNA molecules.

10 III. RNA Structure & Types A. Like DNA, RNA is also a polymer of nucleotides (monomer); each consists of: 1. Simple sugar (ribose) 2. Phosphate group 3. Nitrogenous base

11 a. Four nitrogenous bases exist: i. Adenine (A) ii. Uracil (U) iii. Cytosine (C) iv. Guanine (G)

12 B. In RNA, Adenine (A) pairs with Uracil (U); and Cytosine (C) pairs with Guanine (G)

13 C. While DNA is double stranded, RNA has just one strand = single stranded

14 RNA contains the sugar 1. ribose. 2. deoxyribose. 3. glucose. 4. lactose. 0% 0% 0% 0% Answer Now ribose. deoxyribose. glucose. lactose. 20

15 D. 3 differences of RNA compared to DNA 1. Sugar= ribose; not deoxyribose 2. Single stranded not double stranded 3 RNA uses uracil (U); DNA uses the base thymine (T)

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17 A base that is present in RNA but NOT in DNA is 1. thymine. 2. uracil. 3. cytosine. 4. adenine. 0% 0% 0% 0% Answer Now thymine. uracil. cytosine. adenine. 20

18 How many main types of RNA are there? hundreds 4. thousands 0% 0% 0% 0% Answer Now 1 3 hundreds thousands 20

19 E. 3 types of RNA: 1. mrna (messenger RNA) - carries info from nucleus (copies from DNA) to the ribosomes in a three letter genetic code = codon

20 2. trna (transfer RNA) brings specific amino acids to ribosomes by matching mrna; three nitrogenous bases that are complementary to codon = anticodon

21 3. rrna (ribosomal RNA) structural and functional part of ribosomes

22 So. One more time. Protein Synthesis has 2 major phases.. Transcription Translation

23 IV. Phase #1 (of 2) of protein synthesis: RNA Transcription (DNA RNA): occurs in nucleus of the cell A. Transcribe: to make a copy 1. DNA instructions (encoded in genes) is transcribed into mrna

24 2. mrna can leave the nucleus and go to ribosomes in the cytoplasm Eukaryotes

25 Prokaryotes

26 When DNA is wrapped around histones (forming a nucleosome), DNA can not be transcribed into RNA

27 3. Special base sequences in DNA are recognized by an enzyme as start and stop signals a. Start sequence called promoter region of DNA b. Start Codon = AUG (Methionine)

28 B. Details of the Process 1. Step 1: RNA polymerase attaches to DNA at the promoter region (site where DNA code signals start copying here ). Unzips separates the 2 DNA strands.

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30 2. Step 2: RNA polymerase moves along the DNA strand (uses only 1 strand as a template). a. It synthesizes the mrna strand by adding new free RNA nucleotides (complementary A-U; C-G)

31 b. Remember there aren t T bases in RNA i. C binds with G ii. A of the DNA binds with U of the RNA

32 c. Additional Information (if you were curious) The antisense strand of DNA is read by RNA polymerase from the 3' end to the 5' end during transcription (3' 5'). The complementary RNA is created in the opposite direction, in the 5' 3' direction, matching the sequence of the sense strand. This directionality is because RNA polymerase can only add nucleotides to the 3' end of the growing mrna chain. This use of only the 3' 5' DNA strand eliminates the need for the Okazaki fragments that are seen in DNA replication. This removes the need for an RNA primer to initiate RNA synthesis, as is the case in DNA replication.

33 cricao/transcription.swf

34 Covalent Bonds Form between nucleotides 5 3 direction RNA polymerase can only add nucleotides to the 3' end of the growing mrna chain

35 What is produced during 1. RNA molecules 2. DNA molecules 3. RNA polymerase 4. proteins transcription? 0% 0% 0% 0% Answer Now RNA molecules DNA molecules RNA polymerase proteins 20

36 3. Step 3: When RNA polymerase reaches the end of the gene, or "STOP" code on the DNA, it detaches from the DNA a. Completed mrna strand (single stranded) peels away (rate: 60 nucleotides added/second)

37 4. Step 4: DNA re-zips (hydrogen bonds reform)

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39 5. Step 5: RNA is then edited; introns are removed and exons are spliced together a.introns-sequences of nucleotides in DNA that are not involved in coding for proteins b. Exons-DNA sequences that code for proteins; they are expressed in the synthesis of proteins

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41 snrnps (small nuclear ribonucleoprotein particles, complexes of snrnas and proteins)

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44 A region of a DNA molecule that indicates to an enzyme where to bind to make RNA is the 1. intron. 2. exon. 3. promoter. 4. codon. 0% 0% 0% 0% Answer Now intron. exon. promoter. codon. 20

45 6. Step 6: Edited mrna leaves the nucleus and goes to a ribosome in the cytoplasm (End of Transcription)

46 Which strand was copied? A or B YES, Strand B. How do you know? 46

47 DNA Transcription Video Protein Synthesis Active Art-Resource Disk Ch 12-3

48 Which of the following are copied from DNA? 1. mrna only 2. mrna, trna, and rrna 3. mrna and trna only 4. proteins 0% 0% 0% 0% Answer Now mrna only mrna, trna, and rrna mrna and trna only proteins 20

49 V. The Genetic Code A. Proteins are made by joining amino acids into long chains called polypeptides. 1. The language of mrna instruction is called the genetic code. 2. The code is written in a language that has only 4 letters (A, C, G, U). 3. Each word in the language is only 3 bases long

50 4. Codon = three consecutive nitrogenous bases that specify a single amino acid (3 letter words). a. There are start (AUG) and stop (UGA, UAA, or UAG) codons (Fig )

51 Example of RNA Sequence: Codons = The amino acids = UCGCACGGU UCG-CAC-GGU Serine - Histidine - Glycine

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55 5. If AUG is the start codon, what amino acid will always be at the beginning? a. Start codon = Methionine

56 6. Use the chart to identify the amino acid for the codons below. a. UAA = b. CGA = c. CUU = d. UGU = e. CCG = Stop Arginine Leucine Cysteine Proline

57 7. You try! Separate the RNA strand below into codons: AUGGCUAACUAA AUG-GCU-AAC-UAA

58 AUG-GCU-AAC-UAA What is the amino acid sequence (Use chart) Methionine (start) Alanine Asparagine Stop