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DNA Chapter 10 – Ms. Colabelli. DNA  Holds our genetic information  Like a library  Important for mitosis to occur  Biologists had to discover the.

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Presentation on theme: "DNA Chapter 10 – Ms. Colabelli. DNA  Holds our genetic information  Like a library  Important for mitosis to occur  Biologists had to discover the."— Presentation transcript:

1 DNA Chapter 10 – Ms. Colabelli

2 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

3 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

4 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

5 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

6 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

7 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

8 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

9 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

10 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

11 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

12 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

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

14 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

15 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

16 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

17 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

18 Replicating DNA  Step 3: Once the DNA is replicated, the DNA polymerase releases

19 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?

20 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

21 Protein Synthesis  Two parts process to make a protein from a segment of DNA  Part one: Transcription  DNA  RNA  Part two: Translation  RNA  Protein

22 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

23 RNA  Three types of RNA  mRNA  Messenger RNA  rRNA  Ribosomal RNA  tRNA  Transfer RNA

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

25 RNA  Ribosomal RNA  RNA found in ribosomes (organelles in the cell)

26 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

27 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

28 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

29 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

30 The Genetic Code  Each three letter codon represents an amino acid  DNA = AGCGTGCCAATT  RNA = UCG-CAC-GGU-UAA  Amino acids = Ser-His-Gly-STOP

31 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

32 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

33 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

34 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


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