Chapter 10 The Molecular Basis of Inheritance The Molecular Basis of Inheritance

codes for the Specific Sequence of Amino Acids in a Amino Acids determine the Protein’s Shape, which determine its Function. Proteins function as Biological Reactions Enzymes.

The double helix

Evidence of DNA Transformation - the process of transferring an inherited trait by an extract of DNA (Griffith) Mouse A is injected with live smooth pneumococcus He dies.

Mouse B is injected with live rough pneumococcus. He lives. The smooth pneumococcus are heat-killed and injected into Mouse C. He lives

Mouse D was injected with the mixture of heat-killed smooth pneumococcus and live rough pneumococcus. WHY? Transformation - transfer of genes from smooth to rough pneumonococcus

Smooth pneumoncoccus are virulent. Hard to kill by immune response Presence of slime capsule Rough pneumococcus are nonvirulent. Can be destroyed by immune response No slime capsule Transformation

Bacterial Transformation

5th Hour’s Incredible Work!!! Class of 2003!

5th Hour 2014

STRUCTURE OF A VIRUS *Nucleic acid core of DNA or RNA *Capsid *Envelope *Extensions, filaments, or tail fibers *Bacteriophage

Hershey and Chase used radioactive markers to label the protein and DNA in a bacteriophage. = protein = DNA Phages infect the bacteria

Intracellular Extracellular

Viruses infecting a bacterial cell Phage head Tail Tail fiber DNA Bacterial cell 100 nm

Watson & Crick

Base pairing in DNA H N H O CH 3 N N O N N N NH Sugar Adenine (A) Thymine (T) N N N N Sugar O H N H N H N O H H N Guanine (G) Cytosine (C)

Using Franklin’s Data Purine + Purine: too wide Pyrimidine + pyrimidine: too narrow Purine + pyrimidine: width Consistent with X-ray data

Rosalind Franklin and her X-ray diffraction photo of DNA (a) Rosalind Franklin Franklin’s X-ray diffraction Photograph of DNA (b)

Complementary Base Pairing: Chargaff’s Rule AT C G A particular organism is 20% adenine then how much: T= C= G= 20% 30%

The double helix

A model for DNA replication: the basic concept (layer 4) (a) The parent molecule has two complementary strands of DNA. Each base is paired by hydrogen bonding with its specific partner, A with T and G with C. (b) The first step in replication is separation of the two DNA strands. (c) Each parental strand now serves as a template that determines the order of nucleotides along a new, complementary strand. (d) The nucleotides are connected to form the sugar-phosphate backbones of the new strands. Each “daughter” DNA molecule consists of one parental strand and one new strand. A C T A G A C T A G A C T A G A C T A G T G A T C T G A T C A C T A G A C T A G T G A T C T G A T C T G A T C T G A T C

Helicase Single binding protein Replication Fork Topoisomerase

Helicase RNA primer Polymerase III 3’ 5’ 3’ Polymerase I 5’ 3’ 5’ RNA Primase 5’ 3’ DNA Polymerase III attaches the nucleotides in a 5’ to 3’ direction only.

3’ 5’3’ 5’ Polymerase III Okazaki Fragment Polymerase III DNA Ligase 3’ 5’ Polymerase I

Which Model of Replication????

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Nucleotide excision repair of DNA damage Nuclease DNA polymerase DNA ligase A thymine dimer distorts the DNA molecule. 1 Repair synthesis by a DNA polymerase fills in the missing nucleotides. 3 DNA ligase seals the Free end of the new DNA To the old DNA, making the strand complete. 4 A nuclease enzyme cuts the damaged DNA strand at two points and the damaged section is removed. 2

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Telomeres 1 µm

Enzymes Involved in DNA Replication Helicase - separates the two DNA strands by making a replication fork. DNA Polymerases (III and I) - binds the free nucleotides to the unzipped strand; replaces the RNA Primer with DNA nucleotides Single Binding Proteins – keeps the unzipped strands from tangling Topoisomerase – helps relive strain in helix RNA Primase – lays down the RNA primer Ligase – bonds Okazaki fragments after primer is removed

Enzymes Involved in DNA Replication

Blueprint for Proteins Proteins Function as Enzymes Enzymes make Chemical Rxns Go Thus! DNA is the Blueprint for life!!

Avery’s Discovery of what molecule is responsible for Transformation

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Incorporation of a nucleotide into a DNA strand New strandTemplate strand 5’ end 3’ end Sugar A T Base C G G C A C T P P P OH P P 5’ end 3’ end 5’ end A T C G G C A C T 3’ end Nucleoside triphosphate Pyrophosphate 2 P OH Phosphate

DNA NUCLEOTIDE = Phosphate = Deoxyribose = Adenine = Guanine = Thymine = Cytosine PurinesPyrimidines