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DNA "The Blueprint of Life".

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Presentation on theme: "DNA "The Blueprint of Life"."— Presentation transcript:

1 DNA "The Blueprint of Life"


3 DNA stands for... DeoxyriboNucleic Acid

4 Important Scientists that determined DNA’s Importance
Frederick Griffith – bacterial transformation Oswald Avery – DNA = key to transformation Alfred Hershey & Martha Chase Bacteriophage transformation experiment Erwin Chargaff – base-pairing rules

5 Discovering DNA: A Team Effort
Frederick Griffith (1928) Question: How do bacteria make people sick? Answer: Transformation

6 Transformation Process in which one strain of bacteria is changed by a gene(s) from another strain of bacteria

7 Oswald Avery (1944) Question: Which molecule is important for transformation? Answer: DNA stores & transmits genetic info from 1 generation to the next

8 Hershey & Chase (1952) Question: Are genes made of DNA or protein?
Experiment: Which part of a bacteriophage enters the bacterium? Answer: DNA

9 Hershey/Chase Experiment

10 Important Scientists in the “Race for the Double Helix”
Maurice Wilkins & Rosalind Franklin X-ray diffraction DNA must be a some type of spiral (helix) DNA’s diameter is constant and stable

11 DNA FACTS established by James Watson and Francis Crick
Shape of a double helix

12 What is a Gene? A length of DNA on a chromosome
May be in several parts Exon – the expressed parts of the DNA sequence Intron – the intervening, “junk DNA”, not expressed Parts are cut, put together and then used to make RNA and proteins

13 DNA: codes for your genes  (traits) made of repeating subunits called nucleotides

14 What is a nucleotide? Has three parts: PHOSPHATE DEOXYRIBOSE (sugar)

15 Base-Pair Rule Adenine <==> Thymine Guanine <==> Cytosine
The sides of the DNA ladder are phosphate & sugar held together by  hydrogen bonds

16 Base Pair Rule One side:     A   T   A      T   C   A      T   G   C      G   G   G Other side:


18 How the Code Works The combination of A,T,G,C determines what traits you might have, for ex. C A T C A T   =  purple hair T A C T A C  =  yellow hair

19 Think of the bases of DNA like letters. Letters form words
Think of the bases of DNA like letters. Letters form words.... Words form sentences....                 *endless                combinations

20 Let's Review What We Know About DNA
1.  DNA stands for:   De _____ ribo ______  acid 2.  What is the shape of DNA? _______________ 3.  Who established the structure of DNA?  ____________ 4.  Adenine always pairs with _______________ 5.  The sides of the DNA ladder are deoxyribose and _____ 6.  Guanine always pairs with _____________ 7.  What is the complimentary sequence:   A A T  G  C A 8.  The two sides of DNA are held together by _______ bonds. 9.  DNA is composed of repeating subunits called ______________________ 10.  What are the 4 bases that make up the rungs of the DNA ladder? _______________________________________

21 DNA Replication

22 Replication Facts DNA has to be copied before a cell divides
DNA is copied during the S or synthesis phase of interphase New cells will need identical DNA strands

23 Synthesis Phase (S phase)
S phase during interphase of the cell cycle Nucleus of eukaryotes Mitosis -prophase -metaphase -anaphase -telophase G1 G2 S phase interphase DNA replication takes place in the S phase.

24 DNA Replication Begins at Origins of Replication
Two strands open forming Replication Forks (Y-shaped region) New strands grow at the forks Replication Fork Parental DNA Molecule 3’ 5’

25 DNA Replication Enzyme Helicase unwinds and separates the 2 DNA strands by breaking the weak hydrogen bonds Single-Strand Binding Proteins attach and keep the 2 DNA strands separated and untwisted

26 DNA Replication Before new DNA strands can form, there must be RNA primers present to start the addition of new nucleotides Primase is the enzyme that synthesizes the RNA Primer DNA polymerase can then add the new nucleotides

27 DNA REPLICATION the process by which DNA makes a copy of itself (cell division) SEMI-CONSERVATIVE - half of the old strand is saved

28 DNA Replication Replication = Duplication
Happens in the S phase of Interphase Must replicate before mitosis or meiosis I Part of the double helix is unwound Replication in small pieces (Okazaki fragments) Enzyme stitches pieces together later

29 RNA and Protein Synthesis

30 Structure of RNA Genes – are coded DNA instructions that control production of proteins. 1. consists of a long chain of nucleotides (single strand)) 2. contains sugar ribose 3. contains nitrogenous base Uracil

31 Types of RNA Messenger RNA  mRNA  carries copies of instructions
Ribosomal RNA  rRNA  found in ribosomes where proteins are made. Transfer RNA  tRNA  brings in amino acids to make a protein.

32 Transcription Process in which a sequence of DNA is copied into a complementary sequence of RNA RNA polymerase – enzyme used to open DNA strand and assemble a strand of RNA from DNA template. Promoters –regions of DNA that tells RNA polymerase where to start and stop.


34 Genetic Code Proteins are made by joining AA. (20AA)
Type of protein made is determined by sequence of AA. Code is read three letters at a time 3 Letters in called a codon  codes for an AA.

35 Genetic Code

36 Translation Ribosomes – read instructions from mRNA and makes proteins (Decoding of mRNA) Translation begins when mRNA attaches to ribosome mRNA moves through ribosome 1 codon at a time. Codon is read and tRNA brings in the amino acid that is coded by that codon. *each tRNA carries only one kind of amino acid. *tRNA carries an anticodon that is complimentary to one mRNA codon. Another tRNA comes in with the next amino acid and then the ribosomes bind the AA with a peptide bond. The polypeptide chain grows until the ribosome reaches a stop codon. Then it releases the protein.


38 Review

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