Molecular Basis Of Inheritance

1. Molecular Basis Of Inheritance Timothy G. Standish, Ph. D.

2. 1999 Ig Nobel Prizes • Science Education. The Kansas Board of Education and the Colorado State Board of Education, for mandating that children should not believe in Darwin's theory of evolution. • Medicine. Arvid Vatle of Norway, for carefully collecting, classifying, and contemplating which kinds of containers his patients chose when submitting urine samples. • Chemistry. Takeshi Makino, of the Safety Detective Agency in Japan, for his involvement with an infidelity detection spray that wives can apply to their husbands' underwear. • Biology. Paul Bosland, of the New Mexico State University's Chile Pepper Institute, for breeding a spiceless jalapeno chile pepper. • Managed Health Care. The late George and Charlotte Blonsky of New York City and San Jose, California, for inventing a childbirth device in which the woman is strapped to a circular table that is then rotated at high speed.

3. Capsules Transformation Of BacteriaTwo Strains Of Streptococcus Rough Strain (Harmless) Smooth Strain (Virulent)

4. + Control - Control - Control Experimental Transformation Of BacteriaThe Griffith Experiment OUCH!

5. H H O O OH H2N C C H2N C C NH2 Methionine Cysteine OH OH P O HO CH2 CH2 O Some amino acids contain sulfur, thus proteins contain sulfur, but not phosphorous. SH CH2 Nucleotides contain phosphorous, thus DNA contains phosphorous, but not sulfur. S CH3 H OH The Hershey-Chase Experiement • The Hershey-Chase experiment showed definitively that DNA is the genetic material • Hershey and Chase took advantage of the fact that T2 phage is made of only two things: Protein and DNA

6. T2 grown in S35 containing media incorporate S35 into their proteins Bacteria grown in normal non-radioactive media T2 attach to bacteria and inject genetic material Mix-O-Matic Blending causes phage protein coat to fall off Using S35 When centrifuged, phage protein coats remain in the supernatant while bacteria form a pellet The supernatant is radioactive, but the pellet is not. Did protein enter the bacteria? Is protein the genetic material?

7. T2 grown in P32 containing media incorporate P32 into their DNA Bacteria grown in normal non-radioactive media T2 attach to bacteria and inject genetic material Mix-O-Matic Blending causes phage protein coat to fall off Using P32 When centrifuged, phage protein coats remain in the supernatant while bacteria form a pellet The pellet is radioactive, but the supernatant is not. Did DNA enter the bacteria? Is DNA the genetic material?

8. When DNA Replication Occurs • Typically DNA replication only occurs when cells are preparing to divide (there are some exceptions) • The cell life cycle is well defined and can be divided into four stages: • Gap 1 (G1) - The growth phase in which most cells are found most of the time • Synthesis (S) - During which new DNA is synthesized • Gap 2 (G2) - The period during which no transcription or translation occurs and final preparations for division are made • Mitosis - Cell division

9. Gap 1 - Doubling of cell size. Regular cellular activities. transcription and translation etc. Synthesis of DNA - Regular cell activities cease and a copy of all nuclear DNA is made S Gap 2 - Final preparation for division G1 G2 M Mitosis - Cell division The Cell Life Cycle

10. Old New Old New Conservative - The old double stranded DNA serves as a template for two new strands that are then joined together, thus giving two old strands together and two new strands together Old Old Old New Semi-conservative - In which old strands serve as templates for new strands resulting in double stranded DNA made up of an old and new strand + + Old + New Old + New Old Dispersive - In which sections of the old strands are dispersed in the new strands + DNA Replication:How We Know • There are three ways in which DNA could be replicated:

11. OH NH2 O P HO O N N N N H OH The Meselson-Stahl Experiment • The Meselson-Stahl experiment demonstrated that replication is semiconservative • This experiment took advantage of the fact that nucleotide bases contain nitrogen • Thus DNA contains nitrogen • The most common form of Nitrogen is N14 with 7 protons and 7 neutrons • N15 is called “heavy nitrogen” as it has 8 neutrons thus increasing its mass by 1 atomic mass unit

12. Transfer to normal N14 media Conservative model prediction Dispersive model prediction Semi-conservative model prediction After 20 min. (1 replication) transfer DNA to centrifuge tube and centrifuge Bacteria grown in N15 media for several replications The Meselson-Stahl Experiment X The conservative and dispersive models make predictions that do not come true thus, buy deduction, the semi-conservative model must be true. Prediction after 2 or more replications X X

13. Stages of Replicaton • Replication can be divided into three stages: • Initiation - When DNA is initially split into two strands and polymerization of new DNA is started • Elongation - When DNA is polymerized • Termination - When the new strands of DNA are completed and some finishing touches may be put on the DNA • Both elongation and termination may involve some proof reading of the DNA to ensure that mutations are not incorporated into the newly formed strands of DNA

14. Tools of Replication • There are three major enzymes involved in replication: • DNA Polymerase - Matches the correct nucleotides then joins adjacent nucleotides to each other • Primase - Provides an RNA primer to start polymerization • Ligase - Joins adjacent DNA strands together (fixes “nicks”)

15. More Tools of Replication • Helicase - Unwinds the DNA and melts it • Single Strand Binding Proteins - Keep the DNA single stranded after it has been melted by helicase

16. Initiation • Initiation starts at specific DNA sequences called origins (Ori C = origin in E. coli chromosomes) • Large linear chromosomes may have many origins • First the origin melts (splits into two single strands of DNA) • Next primers are added • Finally DNA polymerase recognizes the primers and starts to polymerize DNA 5’ to 3’ away from the primers

17. Origin of Replication 5’ 3’ 3’ 5’ 3’ 5’ 5’ 3’ 3’ 5’ 5’ 3’ 3’ 5’ 5’ 3’ 3’ 5’ 3’ 5’ Initiation - Forming the Replication Eye

18. Origins of Replication 5’ 3’ 5’ 3’ 3’ 5’ 5’ 3’ 3’ 5’ 5’ 3’ 5’ 3’ 5’ 3’ 5’ 3’ 5’ 3’ Large Linear Chromosomes Have Many Origins Of Replication

19. 3’ 5’ 5’ 3’ 3’ 5’ 3’ Primase - Makes RNA primers 5’ Single strand binding proteins - Prevent DNA from re-anealing Laging Strand 5’ 5’ 3’ 5’ RNA Primers DNA Polymerase 5’ 3’ Helicase - Melts DNA Leading Strand 5’ 3’ Extension - The Replication Fork Okazaki fragment

20. DNA Pol. 5’ 3’ 3’ 5’ Okazaki Fragment RNA Primer DNA Pol. 5’ 3’ 3’ 5’ RNA Primer RNA and DNA Fragments 5’ 3’ 3’ 5’ RNA Primer Nick Extension - Okazaki Fragments DNA Polymerase has 5’ to 3’ exonuclease activity. When it sees an RNA/DNA hybrid, it chops out the RNA and some DNA in the 5’ to 3’ direction. DNA Polymerase falls off leaving a nick. Ligase The nick is removed when DNA ligase joins (ligates) the DNA fragments.

21. DNA Pol. 5’ 3’ 5’ DNA Pol. 5’ 3’ 5’ 5’ DNA Pol. 5’ 3’ MutationWhen Mistakes Are Made Mismatch 3’ to 5’ Exonuclease activity

22. 3’ 5’ 3’ 5’ DNA Pol. Nicks 3’ 5’ DNA Pol. 5’ 5’ 5’ 3’ 3’ 3’ Ligase MutationExcision Repair Endo- Nuclease Thimine Dimer Ligase

23. The End

24. Problem 1 • Question: • If an organisms DNA is 32 % adenine, what percent guanine, thymine, and cytosine are found in the DNA? • Answer: • As adenine always pairs with thymine, there must be 32 % thymine • % GC = 100 % - (T% + A%) = 100 % - (32 % + 32 %) = 36 % • The proportion of guanine to cytosine has to be equal as they pair with one another thus G and C % = 36 % / 2 = 18 % • G = 18 %, T = 32 % and C = 18 %

25. Problem 2 • Question: • Given the following sequence of one strand of DNA, write out the complimentary strand. • 5’AATACGCGATGCTGGTATC3’ • Answer: • 5’AATACGCGATGCTGGTATC3’ • 3’TTATGCGCTACGACCATAG5’