Ch. 16 DNA DNA: the Central Dogma, history, structure Replication

History: timeline, people and their accomplishments Mendel (heredity) Thomas Hunt Morgan (flies, linkage) Griffith (1928) transformation and mice Avery and colleagues (1944): – –proposed DNA as the transforming agent Chargaff (late 40’s-early 50’s) – –base pairing (AT CG) Hershey-Chase (1952) DNA IS hereditary material Watson and Crick (1953) (Franklin) chemical structure of DNA Meselson-Stahl mid 1950’s – –DNA Replication details

Griffith: Transformation

Hershey / Chase Hershey / Chase (the hereditary material is not a protein) Radio- active P and S

Whose rule? A-T C-G Whose rule? A-T C-G Purine? Pyrimidine? You have 6 billion pair in every cell!

How’s it all fit? DNA coiling – Let’s see it!DNA coiling – Let’s see it!

Chargaff’s Rule Purines (A, G, double rings) always pair with Pyrimidines (T, C, single rings) A-T, C-G (& in RNA? ____) Old AP test question: if in a cell the DNA bases are 17% A’s then what are the %’s of the other bases? CUT your PY or Pure Silver (Ag)

DNA Replication: SEMICONSERVATIVE MODEL How did they (Meselson-Stahl) prove this? FIG 16.10

KNOW: Steps of Replication Enzymes Leading and Lagging strands Okazaki Fragments Anti-parallel Video

nucleoside triphosphates This process is fueled by… nucleoside triphosphates Semi-conservative “Bubbles” Replication forks, simultaneous replication **Eukaryotes - multiple origins of replication **Prokaryotes have one

DNA is made from 5’ to 3’ and it is read from 3’-5’. The 3’ end is the end which elongates (grows) Why is this direction important to consider in Replication?

What do the terms 5’ and 3’ mean?

Leading & Lagging strands, made 5’-3’ Okazaki fragments (are of the lagging strand) ENZYMES: helicase, DNA Polymerase, ligase

Enzymes : Enzymes : Helicase Single strand binding proteins Primase (RNA Primer)DNA Polymerase Ligase Nuclease and DNA Polymerase (both are repair enzymes)

Let’s see this in Action Leading Strand (Nobelprize.org)Leading Strand (Nobelprize.org)Nobelprize.org Lagging Strand (Nobelprize.org)Lagging Strand (Nobelprize.org)Nobelprize.org Overall (wiley)Overall (wiley)wiley Overall 3D view (wehi.edu.au or dnai.org) (Youtube has a music version)Overall 3D view (wehi.edu.au or dnai.org) (Youtube has a music version)wehi.edu.au

Telomeres (Ch.16) Telomeres (Ch.16) Unfilled gap left at the ends of the DNA strands due to the use of RNA primers Eventual shortening of DNA over time Dolly, cancer, HeLa cells (telomerase fig16.19)

Enzyme: Telomerase extends the (3’) long strand so the 5’ strand can finish. WOW! ? ? ? Where is telomerase naturally found?

DNA from a single skin cell, if straightened out, would be about six feet long but invisible. Half a gram of DNA, uncoiled, would stretch to the sun. Again, you couldn't see it.

Story Time!! (Due Tuesday Nov. 6) Select a figure, process, topic, or high level vocabulary word from chapter 16 or 17. Your job is to make a poster of your selected topic. -The poster should be kid-friendly as to say an intelligent 8-10 year old would be able to understand it yet make sure that all information communicated is true to the text. - Finally, you may not use English, do the best you can, ask friends, relatives, teachers, etc for help if necessary. Potential topics include but are not limited to the following….. Experiments that identified DNA as the “genetic material”, DNA Structure, DNA Replication, Telomers and telomerase, Transcription, Modification of RNA, Translation, Mutations.

Ch.17 One gene/One polypeptide

Define transcription and translation Compare Prokaryotic and Eukaryotic cells video video

(21 different AA’s)(21 different AA’s) mRNA codemRNA code Ave. protein is 400AA longAve. protein is 400AA long Titin is 30,000AA long! (this is _____ nucleotides?)Titin is 30,000AA long! (this is _____ nucleotides?)

DNA= tripletsDNA= triplets RNA= codonsRNA= codons 5’ to 3’5’ to 3’ Pre- mRNA (primar y transcri pt)Pre- mRNA (primar y transcri pt)

Promoter: TATA BoxPromoter: TATA Box Transcription factorsTranscription factors RNA poly- meraseRNA poly- merase Transcription initiation complexTranscription initiation complex MovieMovieMovie

Finishing the pre- mRNA Introns: (intruding) spliced out Exons: kept, will be Expressed in the cell

snRNP’s identify intronssnRNP’s identify introns Introns are cut out at a SpliceosomeIntrons are cut out at a Spliceosome Final mRNA has only genes that will be tran- scribed in cell no “junk genes”Final mRNA has only genes that will be tran- scribed in cell no “junk genes” videovideovideo

TranslationTranslation The production of polypeptidesThe production of polypeptides On a RibosomeOn a Ribosome tRNA, transfer RNA carries in the amino acids to the ribosome (transfers the A.A)tRNA, transfer RNA carries in the amino acids to the ribosome (transfers the A.A) Read 5’ to 3’

A P E:A P E: Aminoacyl- tRNA synthetaseAminoacyl- tRNA synthetase Peptidyl tRNA binding sitePeptidyl tRNA binding site ExitExit VideoVideoVideo MovieMovieMovie

Termination of the translation

Translation of many polypeptide chains at once

The signal mechanism: signal peptides Free or bound ribosomes?

Coupled transcrip tion and translati onCoupled transcrip tion and translati on

One base difference out of 574 Amino acids (1722 bases)

Nothing formed The wrong protein

Happy Homecoming (again!)Happy Homecoming (again!) Have fun, be safeHave fun, be safe

Repairing mistakes