DNA & RNA Introduction to HE.5.B.2 Describe the Watson-Crick double helix model of DNA, using the base paring rule (adenine-thymine, cytosine-guanine)

Frederick Griffith

Frederick Griffith Birth date: 1879 Birth place:: England, UK Nationality: British Death date: 1941, London, UK Education: University of Liverpool Griffith experiment, 1928 that demonstrated bacterial transformation His discovery showed the central role of DNA in heredity. Discovered the existence of a “transforming factor”.

Griffith Experiment

Griffith Experiment – What is the big deal? TRANSFORMATION: one strand of bacteria had been changed permanently into another. The factor transferred must contain information and since it can be inherited the transforming factor might be a gene. This means: Genetic information could be transferred from one bacterium to another.

Oswald Avery

Oswald Avery Birth date: October 21, 1877 Birth place: Halifax, Nova Scotia Nationality: Canadian (and American citizenship) Death date: February 20, 1955. Nashville, Tennessee Education: Colgate University & Columbia College of Physics and Surgeons. Physician and medical researcher, was nominated for a Nobel multiple times but was never awarded. Questioned the controls used in Griffith experiment Identified DNA as the transforming factor.

Avery’s Experiment Used enzymes to break down proteins, lipids, carbohydrates and other molecules including RNA to find out if transformation would still occur. Transformation did not happen when enzymes destroyed DNA. Avery discovered that the nucleic acid DNA stores and transmits genetic information from one generation of an organism to the next.

Alfred Hershey

Alfred Hershey Birth date: December 4, 1908. Birth place: Owosso, MI Nationality: American Death date: May 22, 1997. New York Education: Michigan State University Bacteriologist and geneticist Received a Nobel prize for the discovery of virus replication His work with Martha Chase provided more evidence that DNA, not protein, was the genetic material of life

Martha Chase

Martha Chase Birth date: November 30, 1927 Birth place: Cleveland Heights, OH Nationality: American Death date: August 8, 2003. Ohio Education: The College of Wooster and PhD from Universidad de Puerto Rico Geneticist Her career was cut short because due to dementia Her work with Alfred Hershey provided more evidence that DNA, not protein, was the genetic material of life

Hershey-Chase Experiment The Hershey-Chase Experiment Alfred Hershey and Martha Chase used different radioactive markers to label the DNA and proteins of bacteriophages. The bacteriophages injected only DNA into the bacteria, not proteins. From these results, Hershey and Chase concluded that the genetic material of the bacteriophage was DNA.

Why was their experiment important? Their experiment concluded the genetic material was DNA not protein.

Erwin Chargaff

Erwin Chargaff Birth date: August 11, 1905 Birth place: Czernowitz, Austria-Hungary Nationality: Austrian (and American citizenship) Death date: June 20, 2002. New York, NY. Education: University of Vienna & Yale University Biochemist, received the Pasteur Medal and National Medal of Science Discovered the Chargaff’s rule that helped determine the structure of DNA.

Rosalind Franklin

Rosalind Franklin Birth date: July25, 1920 Birth place: Notting Hill, United Kingdom Nationality: British Death date: April 16, 1958. London, United Kingdom Education: University of Cambridge. Biophysicist and x-ray crystallographer. Her images were used by Watson and Crick without her permission Her x-ray crystallography images of DNA helped determine the molecular structure of DNA.

DNA X-ray Crystallography

Francis Crick

Francis Crick Birth date: June 8, 1916 Birth place: Northempton, United Kingdom Nationality: British Death date: July 28, 2004. San Diego, CA. Education: University College, London. Molecular biologist, biophysicist and neuroscientist. Received a Nobel prize in 1962. Co-discovered the structure of the DNA molecule with James Watson.

James Watson

James Watson Birth date: April 6, 1928 Birth place: Chicago, IL Nationality: American Death date: - Education: Indiana University, Bloomington Molecular biologist, geneticist and zoologist. Received a Nobel Prize in 1962. Co-discovered the structure of the DNA molecule with Francis Crick.

The component and Structure of DNA What we know at this point: Genes were made of DNA Genes are a set of instructions that determine what the organism is like, its appearance, how it survives, and how it behaves in its environment What are we going to find out: How DNA carry information, how they put the information to work, and how it can be easily copied.

3 Critical things genes can do: Carry information from one generation to the next. Have to put that information to work by determining the heritable characteristics of organisms. Easily copied, because all of a cell’s genetic information is replicated every time a cell divides.

What is DNA made of? NUCLEOTIDES Nucleotides have three parts: Phosphate, Deoxyribose sugar (5 carbon sugar) and Nitrogenous base.

So What is DNA? DNA is a long molecule made of units called nucleotides.

The 4 Nitrogenous Bases: There are four kinds of nitrogenous bases in DNA

Chargaff’s Rules Organism %A %G %C %T A/T G/C %GC %AT Maize 26.8 22.8 23.2 27.2 0.99 0.98 46.1 54.0 Octopus 33.2 17.6 31.6 1.05 1.00 35.2 64.8 Chicken 28.0 22.0 21.6 28.4 1.02 43.7 56.4 Rat 28.6 21.4 20.5 1.01 42.9 57.0 Human 29.3 20.7 20.0 30.0 1.04 40.7 59.3 Grasshopper 41.2 58.6 Sea Urchin 32.8 17.7 17.3 32.1 35.0 64.9 Wheat 27.3 22.7 27.1 45.5 54.4 Yeast 31.3 18.7 17.1 32.9 0.95 1.09 35.8 64.4 E. coli 24.7 26.0 25.7 23.6 51.7 48.3

Chargaff’s Rule The percentage of guanine (%G) and cytosine (%C) bases are almost equal in any sample of DNA. The same is true for adenine (%A) and thymine (%T). [A] = [T] and [G] = [C] Why is this important? It gave scientists clues on the structure of DNA.

X-Ray Evidence X-ray diffraction gave even more clues on the structure of DNA.

So what happens when you add the clues together? X-RAY CRYSTALLOGRAPHY NUCLEOTIDES Organism %A %G %C %T A/T G/C %GC %AT Maize 26.8 22.8 23.2 27.2 0.99 0.98 46.1 54.0 Octopus 33.2 17.6 31.6 1.05 1.00 35.2 64.8 Chicken 28.0 22.0 21.6 28.4 1.02 43.7 56.4 Rat 28.6 21.4 20.5 1.01 42.9 57.0 Human 29.3 20.7 20.0 30.0 1.04 40.7 59.3 CHARGAFF’S RULE

THE DOUBLE HELIX

DNA Summary

DNA Extraction Lab http://learn.genetics.utah.edu/content/labs/extraction/

Let’s build our own DNA model

DNA Replication

The Structure of RNA RNA, like DNA, is made of a long chain of nucleotides. Each nucleotide is made up of a 5-carbon sugar, a phosphate group, and a nitrogenous base.

Figure A represents an RNA nucleotide while figure B represents a DNA nucleotide. Compare both figures How are DNA and RNA nucleotides similar? How are DNA and RNA nucleotides different?

There are three main differences between RNA and DNA: 1) DNA has the sugar ___________________ and RNA has the ___________________ sugar. 2)? 3)?

Compare the RNA nucleotide strand to the DNA nucleotide strand. What are the nitrogenous bases found in RNA? What are the nitrogenous bases found in DNA? How does the RNA strand compares do the DNA strand?

There are three main differences between RNA and DNA: 1) DNA has the sugar ___________________ and RNA has the ___________________ sugar. 2) DNA is ___________ stranded and RNA is ________ stranded. 3)DNA has the base ____________ and RNA has the base ____________.

RNA VS DNA

What are the roles of RNA and DNA? Both molecules are needed in protein synthesis (making proteins). DNA stores and transmits genetic information. The main job of RNA is to transfer the genetic code needed for the creation of proteins from the nucleus to the ribosome. This process prevents the DNA from having to leave the nucleus, so it stays safe.

Types of RNA RNA molecules are involved in just one job – protein synthesis. RNA controls the assembly (putting together) of amino acids into proteins. There are 3 types of RNA molecules that work together to get the job done. Messenger RNA Transfer RNA Ribosomal RNA

Messenger RNA (mRNA)

Transfer RNA (tRNA)

Ribosomal RNA (rRNA)

What is a gene?

TRANSCRIPTION AND TRANSLATION How are proteins made? Proteins happen in 2 steps: TRANSCRIPTION AND TRANSLATION

TransCription TRANSCRIPTION: RNA molecules are made by copying part of the nucleotide sequence of DNA into a complementary sequence in RNA. This step happens in the nucleus and uses an enzyme, called RNA polymerase. During transcription, RNA polymerase binds to DNA and separates the DNA strands. RNA polymerase then uses one strand of DNA as a template (model) from which nucleotides are put together into a strand of RNA. Notice that in RNA the base Thymine is replaced by Uracil. Promoters are sequences in the DNA that tells the RNA polymerase where to bind (attach) to make RNA

TRANSCRIPTION

TransLation The decoding of an mRNA into a polypeptide (chain of amino acids), and it takes place in the ribosomes. During translation, the cells use information from messenger RNA to produce proteins. Translation begins when an mRNA molecule moves from the nucleus of the cell into the cytoplasm and attaches to a ribosome. The genetic code carried by the mRNA is read three letters (nucleotides) at a time. A codon consists of three nucleotides that specify a single amino acid that is to be added to the polypeptide chain. As each codon of the mRNA molecule moves through the ribosome, the proper amino acid is brought into the ribosome by tRNA. In the ribosome, the amino acid is transferred to the growing polypeptide chain. The anticodon is the name of the three unpaired bases on tRNA. The anticodon is complementary to one mRNA codon.

TRANSLATION

RNA molecules at work

How proteins are made: Proteins are made by joining amino acids into long chains called polypeptides. Each polypeptide contains a combination of any or all of the 20 different amino acids found in nature. The properties of proteins are determined by the order in which different amino acids are joined together to produce polypeptides.

How can the code with just four letters carry instructions for 20 different amino acids? This is possible because the genetic code is read three letters at a time. Because there are four different bases, there are 64 possible codons of the genetic code. As you can see on the image below, some amino acids can be specified by more than one codon.

Amino Acid Table

Protein Synthesis