AP Biology Day 27. Wednesday, October 26, 2016

Transcription

1 AP Biology Day 27 Wednesday, October 26, 2016

2 Do-Now 1. Double check Is your unit log complete? Is your lab notebook up to date with scores? Did you write your Unit 4 log standards? Did you begin filling out I II on your 2 Ch. 16 Notes Outline?

3 Announcements Not passing? You must aeend tutoring at least once a week no excep0ons Study Ch carefully Unit 1 quizzes/retakes must be completed à retakes will no longer be accepted for this unit aler this week Failure to turn in major assignments will result in an incomplete grade, even if your percentage is passing

4 CW/HW Assignments 4. Photo 51 WS 5. Ch. 16 Notes Outline 6. Ch. 17 VCN (1) PLANNER 1. Ch. 17 Video CN (choose 1) 2. CH. 16 Quiz do practice questions 3. Submit ALL missing work :o!

5 EssenRal knowledge standards 3.A.1: DNA, and in some cases RNA, is the primary source of heritable information

6 FLT I will be able to: identify what contributions scientists made in the discovery and understanding of DNA describe the process of DNA replication compare and contrast baterial and eukaryotic chromosomes By completing Ch. 16 Lecture Notes

7 Ch. 16: The Molecular Basis of Inheritance

8 Recall: DNA Review DNA is a nucleic acid (made up of nucleordes) It is double stranded and contains deoxyribose The nitrogenous bases are A, C, T, G The structure is a double helix Strong covalent bonds hold the sugar-phosphate backbone together Weaker hydrogen bonds hold the base pairs together DNA is anrparallel and the strands are complementary 8

9 The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again. 9

10 Watson s Pairing of Purines with Pyrimidines was Consistent with Franklin s Data Purine + purine: too wide Pyrimidine + pyrimidine: too narrow Purine + pyrimidine: width consistent with X-ray data

11 The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again. 11

12 III. DNA ReplicaRon DNA Replication = the process of copying DNA This occurs prior to cell division It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material. Watson & Crick 12

13 III. DNA ReplicaRon Watson and Crick reasoned that since the two strands of DNA are complementary, each strand acts as a template for building a new strand in replicaeon New strands form according to base-pairing rules The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again. 13

14 14 III. DNA ReplicaRon

15 III. DNA ReplicaRon B. Models of ReplicaRon 1. Meselson and Stahl Experiments à supported the semiconservaeve model of DNA replicaeon. a. ConservaRve b. SemiconservaRve The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, c. Dispersive you may have to delete the image and then insert it again. 15

16 16 Proposed Models

17 III. DNA ReplicaRon B. Models of ReplicaRon 1. Meselson and Stahl Experiments a. ConservaRve = parent molecule directs synthesis of completely new DNA molecule b. SemiconservaRve c. Dispersive 17

18 III. DNA ReplicaRon B. Models of ReplicaRon 1. Meselson and Stahl Experiments a. ConservaRve b. SemiconservaRve = supported model. Parent strands are separated and replicated. IdenEcal copies are produced due to base-pairing rules. Each DNA is ½ old ½ new c. Dispersive 18

19 III. DNA ReplicaRon B. Models of ReplicaRon 1. Meselson and Stahl Experiments a. ConservaRve b. SemiconservaRve c. Dispersive = Material within the two parental strands is distributed randomly between daughter DNA molecules. 19

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21 SemiconservaRve Model The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again. 21

22 Pair-Share-Respond 1. What is DNA replicaeon? 2. How did the model of DNA imply a method of replicaeon? 3. IdenEfy the three proposed models of DNA replicaeon and what they mean. Which one is the supported model?

23 III. DNA ReplicaRon The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again. 23

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25 III. DNA ReplicaRon C. Steps of ReplicaRon of DNA Begins at origins of replicaeon à two DNA strands are separated, opening up a replicaeon bubble There can be hundreds or even thousands of origins (facilitates rapid replicaron) ReplicaEon occurs in both direceons simultaneously 25

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27 Steps of ReplicaRon ReplicaEon fork = Y-shaped region where new DNA strands are elongaeng Helicases = enzymes that unwind DNA at replicaeon forks 27

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30 Steps of ReplicaRon Single-strand binding proteins = stabilize the single strands (keep in place) Topoisomerase = regulates winding and unwinding of DNA so that replicaeon can occur The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again. 30

31 Steps of ReplicaRon Note: the strands are anrparallel one is 5 à 3, and the other is 3 à 5 Each strand is replicated differently due to this difference 31

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33 Leading Vs. Lagging Strands New nucleordes can only be added to the 3 end of strands New strands form from 5 to 3 33

34 Leading Vs. Lagging Strands The leading strand is the strand with the 3 end open The new strand can easily synthesize in the 5 à3 direcron 34

35 Leading Vs. Lagging Strands The lagging strand has the 5 direcron exposed This makes it more difficult to synthesize in the correct 5 à 3 direcron 35

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37 DNA Polymerase DNA polymerase = Enzyme that adds matching DNA nucleoedes to single DNA strands DNA polymerase only works from 5 à 3 Most DNA polymerases require a primer and a DNA template strand to funceon 37

38 Priming DNA Synthesis RNA primer = short, inieal nucleoede strand that acts as the stareng point for DNA synthesis DNA polymerase replaces the primer with DNA nucleoedes 38

39 Leading Vs. Lagging Strand The leading strand can be synthesized conrnuously since it is in the correct direcron 39

40 Leading Vs. Lagging Strand For the lagging strand, we need to add muleple primers & synthesis will occur in short seceons in the correct 5 à 3 direceon Synthesis occurs disconrnuously 40

41 Leading Vs. Lagging Strand The short seceons = Okazaki fragments DNA ligase connects the fragments 41

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44 *Recap* Helicase unzips DNA (between bases) Forks are at the corners of the replicaron bubble SS binding proteins hold strands in place Topoisomerase regulates coiling issues Primase adds an RNA primer to origins DNA polymerase adds nucleordes DNA ligase connects nucleordes with covalent bonds 44

45 Pair-Share-Respond 1. What is the role of helicase? 2. What is the role of DNA polymerase, and what does it need? 3. In which direceon does DNA polymerase funceon? 4. DisEnguish between the leading and lagging strand in DNA synthesis. 5. What is the role of DNA ligase?

46 Proofreading & Repairing DNA Mismatch Repair DNA polymerases proofread newly made DNA, replacing any incorrect nucleoedes 46

47 Proofreading & Repairing DNA Excision Repair DNA can be damaged by chemicals, radioacrve emissions, X-rays, UV light, and certain molecules (in cigareee smoke for example) In nucleoede excision repair, a nuclease cuts out and replaces damaged stretches of DNA 47

48 Nucleotide Excision & Repair Nuclease DNA polymerase DNA ligase

49 EukaryoRc vs. ProkaryoRc A chromosome consists of a DNA molecule packed together with proteins The bacterial chromosome is a double-stranded, circular DNA molecule associated with a small amount of protein EukaryoRc chromosomes have linear DNA molecules associated with a large amount of protein In a bacterium, the DNA is supercoiled and found in a region of the cell called the nucleoid 49

50 ChromaRn is a complex of DNA and protein, and is found in the nucleus of eukaryorc cells Histones are proteins that are responsible for the first level of DNA packing in chromarn 50

51 Eukaryotic DNA Packing in Chromatin DNA double helix (2 nm in diameter) Nucleosome (10 nm in diameter) Histones Histone tail H1 DNA, the double helix Histones Nucleosomes, or beads on a string (10-nm fiber)

52 Review G C A T Sugarphosphate backbone C C A G T G G T A C Nitrogeno us bases T A Hydrogen bond

53 DNA Replication: Leading and Lagging Strands DNA pol III synthesizes leading strand continuously 3ʹ 5ʹ Parent al DNA 5ʹ 3ʹ 5ʹ Primase synthesizes a short RNA primer DNA pol III starts DNA synthesis at 3ʹ end of primer, continues in 5ʹ 3ʹ direction Lagging strand synthesized Okazaki fragments, later joined by DNA ligase in short 3ʹ 5ʹ

54 Work on assignments or study Ch