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© 2014 Pearson Education, Inc. We will focus on these 3 classic experiments highlighted in this chapter…… Griffith (Frederick) Hershey and Chase (Alfred.

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Presentation on theme: "© 2014 Pearson Education, Inc. We will focus on these 3 classic experiments highlighted in this chapter…… Griffith (Frederick) Hershey and Chase (Alfred."— Presentation transcript:

1 © 2014 Pearson Education, Inc. We will focus on these 3 classic experiments highlighted in this chapter…… Griffith (Frederick) Hershey and Chase (Alfred and Martha) Meselsen and Stahl (Matt and Frank)

2 © 2014 Pearson Education, Inc. 2_1936.jpg Griffith There are unknown heritable substances… Turned to a bacterial pathogen…Streptococcus pneumoniae Is it gram positive or negative?

3 © 2014 Pearson Education, Inc. Figure 13.2 Living S cells (control) Mouse healthy Results Experiment Mouse healthy Mouse dies Living S cells Living R cells (control) Heat-killed S cells (control) Mixture of heat-killed S cells and living R cells Mouse dies Work by Avery identified the transforming substance as DNA

4 © 2014 Pearson Education, Inc. Transformation-did not really understand mechanism Can we do this-pick up DNA from our environment?

5 © 2014 Pearson Education, Inc. Hershey and Chase (1952) Their work pointed to DNA rather than proteins… Bacteriophages what are they???? (worked with one called T2)

6 © 2014 Pearson Education, Inc. Some phages grown in media for a couple hrs with radioactive Sulphur…(which should be incorporated into some proteins Methionine, Cysteine) Other phages grown in media for a couple hrs with radioactive Phosphorus….(which should be incorporated into DNA)

7 © 2014 Pearson Education, Inc. Figure 13.4 Labeled phages infect cells. Batch 1: Radioactive sulfur ( 35 S) in phage protein Experiment Agitation frees outside phage parts from cells. Centrifuged cells form a pellet. Radioactivity (phage protein) found in liquid Batch 2: Radioactive phosphorus ( 32 P) in phage DNA Radioactivity (phage DNA) found in pellet Radioactive protein Radioactive DNA Centrifuge Pellet 12344

8 © 2014 Pearson Education, Inc. Watson-Crick Model predicted…. Each of two daughter molecules would have one parental strand and one newly made! Meselson and Stahl-clever experiment…What did they do??

9 © 2014 Pearson Education, Inc. Figure Conservative model Semiconservative model Dispersive model Predictions: First replicationSecond replication DNA sample centrifuged after first replication DNA sample centrifuged after second replication Bacteria cultured in medium with 15 N (heavy isotope) Bacteria transferred to medium with 14 N (lighter isotope) Less dense More dense Experiment Results Conclusion 1324

10 © 2014 Pearson Education, Inc. Figure 13.1 Watson and Crick _dna.html

11 © 2014 Pearson Education, Inc. What do these terms refer to… How does this replication thing work?? origin of replication helicase topoisomerase replication fork primase and the RNA primer single stranded binding proteins DNA polymerase Search online for stronger and weaker video clips-which one is the very best and the very worst? 1. me the links to your very best and worst (with your group members names) 2.Jot down on the board enough of the web address that we can distinguish which ones are the same

12 © 2014 Pearson Education, Inc. Figure 13.7b 3 end 5 end 3 end 5 end T A C G C G T A 1 2

13 © 2014 Pearson Education, Inc. Figure Single-strand binding proteins Helicase Topoisomerase Primase Replication fork RNA primer

14 © 2014 Pearson Education, Inc. Figure Parental DNA Continuous elongation in the 5 to 3 direction DNA pol III RNA primer Sliding clamp 5 3 Origin of replication Lagging strand Lagging strand Overall directions of replication Leading strand Leading strand Overview Primer

15 © 2014 Pearson Education, Inc. Figure 13.16a Origin of replication Lagging strand Lagging strand Overall directions of replication Leading strand Leading strand Overview What is going to latch on at #1?

16 © 2014 Pearson Education, Inc. Figure 13.16b Primase makes RNA primer. Template strand 1

17 © 2014 Pearson Education, Inc. Figure 13.16b Primase makes RNA primer. RNA primer for fragment 1 Template strand DNA pol III makes Okazaki fragment

18 © 2014 Pearson Education, Inc. Figure 13.16b Primase makes RNA primer. RNA primer for fragment 1 Template strand Okazaki fragment 1 DNA pol III makes Okazaki fragment 1. DNA pol III detaches Where is DNA pol III going to go next??

19 © 2014 Pearson Education, Inc. Figure 13.16c-1 RNA primer for fragment 2 Okazaki fragment 2 DNA pol III makes Okazaki fragment Now you have all these bits what has to happen next? And who does that?

20 © 2014 Pearson Education, Inc. Figure 13.16c-2 RNA primer for fragment 2 Okazaki fragment 2 DNA pol III makes Okazaki fragment 2. DNA pol I replaces RNA with DNA

21 © 2014 Pearson Education, Inc. Figure 13.16c-3 RNA primer for fragment 2 Okazaki fragment 2 DNA pol III makes Okazaki fragment 2. Overall direction of replication DNA pol I replaces RNA with DNA. DNA ligase forms bonds between DNA fragments

22 © 2014 Pearson Education, Inc. Figure Origin of replication Lagging strand Lagging strand Overall directions of replication Leading strand Leading strand Overview Primase makes RNA primer. RNA primer for fragment 1 Template strand Okazaki fragment 1 DNA pol III makes Okazaki fragment 1. DNA pol III detaches RNA primer for fragment 2 Okazaki fragment 2 DNA pol III makes Okazaki fragment 2. Overall direction of replication DNA pol I replaces RNA with DNA. DNA ligase forms bonds between DNA fragments

23 © 2014 Pearson Education, Inc. Figure Origin of replication Lagging strand Lagging strand Overall directions of replication Leading strand Overview Leading strand Lagging strand DNA ligase DNA pol I DNA pol III Primase DNA pol III Primer Lagging strand template Parental DNA Helicase Single-strand binding proteins Leading strand template

24 © 2014 Pearson Education, Inc. Figure 13.17a Origin of replication Lagging strand Lagging strand Overall directions of replication Leading strand Overview

25 © 2014 Pearson Education, Inc. Figure 13.17b Leading strand DNA pol III Primase Primer 5 3 Lagging strand template Parental DNA Helicase Single-strand binding proteins Leading strand template

26 © 2014 Pearson Education, Inc. Figure 13.17c Lagging strand DNA ligaseDNA pol I DNA pol III

27 © 2014 Pearson Education, Inc. Figure Pyro- phosphate New strand Phosphate Nucleotide 5 3 Template strand Sugar Base DNA poly- merase T A T CG A T CG C P P P P P i P i 2 A T CG A CG C

28 © 2014 Pearson Education, Inc. Question 1. True of Leading strand, Lagging strand, or Both???? Daughter strand elongates away from replication fork Synthesizes 5’ to 3’ Multiple primers needed Made in segments Made continuously Daughter strand elongates toward replication fork

29 © 2014 Pearson Education, Inc. True of Leading strand, Lagging strand, or Both???? Daughter strand elongates away from replication fork Lag Synthesizes 5’ to 3’ Both Multiple primers needed Lagg Made in segments Lag Made continuously Lead Daughter strand elongates toward replication fork from Lead

30 © 2014 Pearson Education, Inc. Question 2. The diagram below shows a replication bubble with synthesis of the leading and lagging strands on both sides of the bubble. The parental DNA is shown in dark blue, the newly synthesized DNA is light blue, and the RNA primers associated with each strand are red. The origin of replication is indicated by the black dots on the parental strands. Rank the primers in the order they were produced. If two primers were produced at the same time, overlap them.

31 © 2014 Pearson Education, Inc. Question 3. The lagging strand is synthesized as a series of segments called Okazaki fragments Fragment A is the most recently synthesized and Fragment B will be synthesized next in the space between primers A and B Start DNA polymerase III binds to 3’ end of primer B A. DNA polymerase I replaces primer with DNA B. DNA polymerase I binds to 5’ end of primer A C. DNA polymerase III moves 5’ to 3’ adding DNA nucleotides to primer B D. DNA ligase links fragments A and B

32 © 2014 Pearson Education, Inc. In an analysis of the nucleotide composition of DNA, which of the following will be found? A = G and C = T G + C = T + A A = C A + C = G + T

33 © 2014 Pearson Education, Inc. Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine? 31% 42% 8% 16% It cannot be determined from the information provided.


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