DNAChapter 10 – Ms. Colabelli

DNA

Holds our genetic information Like a library

Important for mitosis to occur

Biologists had to discover the chemical nature of DNA to determine that it is responsible for our genetic information

Griffith and Transformation

Transformation: when a strain of bacteria is changed by a gene or genes from another bacteria

Experiment Inject mice with bacteria S.pneumoniae

Smooth colonies = virulent (disease causing) Rough colonies = harmless bacteria

Griffith and Transformation If the virulent colonies were killed with heat & mixed with

harmless bacteria, the harmless bacteria get transformed into virulent bacteria

Some factor of the harmless bacteria was transformed to become virulent

http://www.quia.com/files/quia/users/hlrbiology/Animations/08_DNA_and_Proteins/Griffith_Mouse_Experiment.swf

Avery and DNA

Wanted to repeat Griffith’s experiment

Treated heat killed virulent bacteria with enzymes Used two enzymes that destroyed proteins, and

RNA Another enzyme destroyed ONLY DNA (nucleic

acids) Lethal Virus

Avery and DNA Results

Results: bacteria treated with DNA destroying enzyme did not transform harmless bacteria into virulent bacteria

It must be the DNA that stores the genetic information from one generation to the next

Lethal Lethal Non Lethal

Lethal Virus

Hershey-Chase

Bacteriophage: a virus that infects bacteria ONLY

Scientists wanted to see what gets injected into a bacteria to cause infection Used a radioactive

marker DNA and protein

Hershey Chase Results After infection, the bacteria that had radioactive marker

on DNA showed that it is the DNA that is inserted into the bacteria

Results: genetic material of the bacteriophage was DNA and not protein

http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter14/animations.html#

DNA Structure

Rosalind Franklin Scientist that worked with X-ray diffraction Used X-rays on a portion of DNA and the results

showed an X pattern

DNA Structure

Watson & Crick Scientists that

were able to figure out what Rosalind’s X-ray pattern meant

Result: DNA has a double helix pattern where the nitrogenous bases face each other in the middle

DNA Structure

DNA has a double helix pattern The sides of the ladder are

the sugar and phosphate Rungs of the ladder are the

nitrogenous bases paired up The bond between two

nitrogenous bases is a hydrogen bond

DNA Structure

Backbone of DNA is the sugar and phosphate

Nitrogenous bases stick out of side to form latter rungs These bases are

repeated in a pattern that form our genetic code

DNA Structure

Monomer of DNA is a nucleotide Phosphorous group 5-carbon sugar Nitrogenous base

4 Nitrogenous bases in DNA Adenine Guanine Thymine Cytosine

DNA Structure

Chargaff’s Rule Scientist that discovered a peculiar trend between

the 4 bases Same percentage of Adenine as Thymine Same percentage of Guanine as Cytosine

Adenine binds to Thymine

Guanine binds to Cytosine

DNA Replication

Process by which DNA is copied in a cell before division

Each strand of DNA is needed to be a template for a new strand of DNA to be produced

Since you can use one strand to make the other side, they are said to be complementary

Replicating DNA

Step 1: DNA molecules separates into two strands with help from enzyme named helicase Breaks hydrogen bonds between bases Creates a replication fork

Replicating DNA

Step 2: Enzyme named DNA polymerase adds new nucleotides to other side of template strand This forms new hydrogen bonds

DNA Polymerase can only move in one direction (3’-5’) so you have one strand that leads and one that lags To join the gaps between lagging strands and enzyme (ligase) come and binds them

Replicating DNA

Step 3: Once the DNA is replicated, the DNA polymerase releases

http://www.youtube.com/watch?v=zdDkiRw1PdU

How Replication Occurs Enzymes help make new strands of DNA

Helicase “unzips” the DNA, separating the base pairs DNA polymerase adds new bases to pair up with the

template This enzyme also proofreads to make sure everything matches

What would be the matching bases to the part of DNA shown below?

Eukaryotes vs. Prokaryotes

Eukaryotes Long rod shaped chromosomes Replication starts in certain points on

the chromosome Try to be as effective and time efficient

Prokaryotes Circular chromosome Replication begins in one place Ends once the DNA polymerase meets

its starting point Very fast

Protein Synthesis

Two parts process to make a protein from a segment of DNA

Part one: Transcription DNA RNA

Part two: Translation RNA Protein

RNA

Made of nucleotides

Three differences between DNA & RNA Sugar

DNA = deoxyribose sugar

RNA = ribose sugar

RNA is single stranded RNA uses Uracil

instead of Thymine to bond with Adenine

RNA

Three types of RNA mRNA

Messenger RNA rRNA

Ribosomal RNA tRNA

Transfer RNA

RNA

Messenger RNA This is a copy of complimentary strand of

DNA Eventually will code for a protein to be

made

RNA

Ribosomal RNA RNA found in ribosomes (organelles in the

cell)

RNA

Transfer RNA Help produce a protein from mRNA Brings amino acids (monomer of protein) to

ribosome to bond them together and make a whole protein

Transcription Taking DNA and making an RNA copy

Step 1: RNA polymerase binds to a promoter and unwinds the strands

Step 2: RNA polymerase adds free RNA nucleotides that are complimentary to DNA strands

Once this is made it is called pre-mRNA

Step 3: RNA polymerase reaches a termination signal and releases

http://www.zerobio.com/drag_oa/protein/overview.htm

RNA Editing Pre-mRNA is a rough draft to the final copy of mRNA

Some parts of pre-mRNA are not needed to make a certain protein These unnecessary parts are called introns Introns get cut out of pre-mRNA

Before leaving the nucleus, mRNA needs to get a 5’ cap and poly A tail to finalize the RNA strand

The Genetic Code

Proteins are made of amino acids

There are 20 amino acids

In order to make a protein from a strand of mRNA, the mRNA is read in a 3 letter sequence called codons

The Genetic Code Each three letter codon represents an amino acid

DNA = AGCGTGCCAATT RNA = UCG-CAC-GGU-UAA Amino acids = Ser-His-Gly-STOP

The Genetic Code Each three letter codon represents an amino acid

DNA = TACCGTCCGGTCATC RNA = AUG-GCA-GGC-CAG-UAG Amino acids = Met-Ala-Gly-Gln-STOP

http://learn.genetics.utah.edu/content/molecules/transcribe/

Translation

Taking mRNA and making a protein

Occurs in the cytoplasm on a ribosome

Step 1: 2 ribosomal subunits bind to mRNA and a tRNA molecule. The tRNA molecule matches to the codon of the mRNA sequence

The first amino acid is always Methionine

If mRNA = AUG, then tRNA = UAC

The tRNA has the anti-codon

Translation

Step 2-3: As tRNA brings new amino acids to the ribosome, past ones break off leaving just amino acids bonded to each other

Step 4: This continues until one of the three STOP codons is met

Step 5: ribosomal units break down and the amino acid strand goes through protein folding

http://www.zerobio.com/drag_oa/protein/translation.htm

The Human Genome

The entire genome sequence of a human

3.2 billion base pairs in our 23 chromosomes

We now need to learn what each of these sequences code for

This will help with curing diseases and prevention of others

http://www.youtube.com/watch?v=TCsWBMMXewE http://www.youtube.com/watch?v=F5LzKupeHtw