DNA Chapter 12

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 containing virus for pneumonia Smooth colonies = have bacterial infection Rough colonies = harmless bacteria

Griffith and Transformation If the virulent colonies were killed with heat and mixed with harmless bacteria, then the harmless bacteria get transformed into virulent bacteria Some factor of the bacteria was transformed to harmless bacteria 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 One enzyme destroyed RNA and proteins Another enzyme destroyed ONLY DNA Lethal Virus

Avery and DNA Lethal Virus Results showed that bacteria treated with DNA destroying enzyme did not transform harmless bacteria into virulent bacteria It is the DNA that stores the genetic information from one generation to the next Lethal Lethal Non Lethal

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 for DNA and protein

Hershey Chase After infection, the bacteria that had radioactive marker on DNA showed that it is the DNA that is inserted into the bacteria Results: DNA from the virus is what causes infection Hershey-Chase Experiment

DNA Structure Monomer of DNA is a nucleotide 5-carbon sugar Phosphorous group Nitrogenous base 4 Nitrogenous bases in DNA Adenine Guanine Thymine Cytosine

DNA Structure Backbone of DNA is the sugar and phosphate Nitrogenous bases stick out of side to form ladder rungs These bases are repeated in a pattern that form our genetic code

DNA Structure Chargaff’s Rule Scientist that discovered a pattern between the 4 bases Same percentage of Adenine as Thymine Same percentage of Guanine as Cytosine Scientists still not sure how they match up though

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 understand Rosalind’s X-ray picture Result: DNA has a double helix pattern where the nitrogenous bases face each other

DNA Structure DNA has a double helix pattern Looks like a ladder twisted up The sides of the ladder are the sugar and phosphate and the rungs of the ladder are the nitrogenous bases paired up The adenine binds to thymine The guanine binds to cytosine This concluded Chargaffs’s rule  base pairing

DNA and Chromosomes Prokaryotes Eukaryotes Lack nucleus and organelles DNA floats as a circle in the cytoplasm Eukaryotes 1000 times more DNA than prokaryotes DNA is located in nucleus Specific number of chromosomes Ex: Humans have 46 chromosomes

DNA and Chromosomes DNA Length Chromosome Structure DNA is very long DNA is coiled up into a very small space because it is in chromatin form Chromosome Structure Tightly packed chromatin is wrapped around small proteins called histones When chromatin gets super coiled you create a chromosome

DNA Replication 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

Duplicating DNA Before mitosis occurs, DNA needs to be duplicated first during interphase When DNA duplicates, its called replication DNA molecules separates into two strands, then produces two new complementary strands following the rules of base pairing Each strand serves as a template for the new strand

How Replication Occurs Enzymes help make new strands of DNA One enzyme called 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? https://www.youtube.com/watch?v=zdDkiRw1PdU

RNA & Protein Synthesis Sections 3-4 RNA & Protein Synthesis

Structure of 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

Types of RNA Three types of RNA mRNA rRNA tRNA Messenger RNA Ribosomal RNA tRNA Transfer RNA

Types of RNA Messenger RNA This is a copy of complimentary strand of DNA Eventually will code for a protein to be made

Types of RNA Ribosomal RNA RNA found in ribosomes (organelles in the cell) Ribosomes are the factory for protein synthesis

Types of 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 Occurs in the cell’s nucleus RNA polymerase opens the DNA and adds RNA copy to the template Once this is made it is called pre-mRNA

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 protein These unnecessary parts are called introns Introns get cut out of pre-mRNA Before leaving the nucleus, mRNA needs to get a cap and tail to finalize the RNA strand

The Genetic Code Proteins are made of 20 possible 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 = AGCGTGCCA RNA = Codons = Amino acids =

The Genetic Code Each three letter codon represents an amino acid DNA = TACCGTCCGGTCATC RNA = Codons = Amino acids = DNA = AGCGTGCCAATT http://learn.genetics.utah.edu/content/molecules/transcribe/

The Genetic Code RNA knows when to start and stop based on the codons read There is ONE start codon: AUG There are THREE stop codons: UAA, UAG, UGA

Translation Taking mRNA and making a protein Occurs in the cytoplasm on a ribosome tRNA brings specific amino acids to ribosome If mRNA = AUG, then tRNA = UAC The tRNA has the anti-codon

Translation As new tRNA brings amino acids to the ribosome, past ones break off leaving just amino acids bonded to each other This continues until one of the three STOP codons is met Finished amino acid strand goes through protein folding

Mutations Changes in the DNA sequence that affect the cell Two types of mutations Gene mutation Chromosomal mutation

Gene Mutation Point mutation Frameshift mutation A change in one nucleotide in a DNA sequence Occur only in a single point of the DNA Can sometimes be a problem Frameshift mutation A change in the reading frame of DNA Since DNA is read in 3 letter codons, if there is an insertion, deletion, or large change in these codons the frame is changed

Chromosomal Mutation A change in the number of chrom0somes in the cell Four types Deletion Duplication Inversion Translocation