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11 Structure & Function of DNA Understanding Growth & Development.

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Presentation on theme: "11 Structure & Function of DNA Understanding Growth & Development."— Presentation transcript:

1 11 Structure & Function of DNA Understanding Growth & Development

2 The Structure of DNA DNA stands for: deoxyribonucleic acid DNA is: the molecule of life and is found in every organism DNA stores: information for proper cellular function 22

3 The Structure of DNA, cont. The complete DNA molecule is arranged in a structure called a double helix Double helix – 2 coiled strands; twisted ladder 3

4 The Structure of DNA, cont. DNA is: a large polymer that contains the elements C,H,O,N & P Polymer structure is made of single units (monomers) called nucleotides 3 components of a nucleotide: 5-carbon sugar Phosphate group Nitrogen-containing base 4

5 The Structure of DNA, cont. Sides of ladder: Deoxyribose a 5-carbon (pentose) sugar Phosphate group Rungs of ladder: 2 nitrogen-containing bases joined with a hydrogen bond 5

6 The Structure of DNA, cont. Nitrogen Bases: Cytosine - C Guanine - G Adenine - A Thymine - T 6

7 77 DNA Nucleotide O=P-O O Phosphate Phosphate Group Group N Nitrogenous base (A, G, C, or T) (A, G, C, or T) CH2 O C1C1 C4C4 C3C3 C2C2 5 5-Carbon Sugar 5-Carbon Sugar (deoxyribose) (deoxyribose) O

8 8 8 Nitrogen-containing Bases Double ring PURINESDouble ring PURINES Adenine (A) Guanine (G) Single ring PYRIMIDINESSingle ring PYRIMIDINES Thymine (T) Cytosine (C) T or C A or G

9 Base-Pairings The DNA of all organisms follows the rule of base-pairing: Cytosine always bonds with Guanine and Adenine always bonds with Thymine 9

10 10 Base-Pairings Three hydrogen bonds required to bond Guanine & Cytosine CG 3 H-bonds

11 11 T A Two hydrogen bonds are required to bond Adenine & Thymine

12 12 DNA P P P O O O 1 2 3 4 5 5 3 3 5 P P P O O O 1 2 3 4 5 5 3 5 3 G C TA

13 13 Historical Landmarks in the Discovery of DNA Historical Landmarks in the Discovery of DNA 13

14 14 1868-Switzerland Johann Friedrich Miescher Found it when working with white blood cells that he took from pus drained out of a surgical wound.

15 1920-London Frederick Griffith Found that bacteria could acquire something from each other to turn harmless bacteria into deadly bacteria, though he wasn't sure what. 15

16 1944-New York Oswald Avery Led a team that assessed Griffith’s work Discovered the molecule DNA was what had caused the change. 16

17 1950-New York Edwin Chargaff Found that the amount of adenine was almost equal to the amount of thymine, and that the amount of guanine was almost equal to the amount of cytosine. Thus you could say: A=T, and G=C. This discovery later became Chargaff’s Rule. 17

18 1952-London Rosalind Franklin and Maurice Wilkins Were able to obtain an x-ray image of crystalized DNA It showed a ladder with rungs twisted in an “X” shape indicating DNA had a helix shape. 18

19 19

20 1953-London James Watson and Francis Crick Published their findings about the structure of DNA Watson, Crick and Wilkins received a Nobel Prize for their work in 1962 20

21 All about you and your chromosomes Humans- 46 chromosomes-23 pairs 22 autosomal pairs or 44 chromosomes 1 pair of sex chromosomes-2 sex chromosomes Xx-girl xy- boys X in eggs only Sperm will have either an X or a Y 21

22 DNA Replication DNA structure in : Prokaryotes - single, circular piece; found in cytoplasm Eukaryotes - arranged in multiple threads called chromosomes; found in nucleus 22

23 DNA Replication, cont. Number of chromosomes varies depending on organism: Fruit Fly - 8 Humans – 46 Chimpanzees - 48 Aquatic Rat - 92 23

24 DNA Replication, cont. Genes: sections of DNA on the chromosomes Genes: code for certain proteins that provide instructions for cellular activity 24

25 DNA Replication, cont. Each cell of any type of organism must be able to make copies of its DNA to pass on to daughter cells Replication – when DNA makes a copy of itself Both strands of DNA are complementary to each other Each serve as a template to make a new strand 25

26 DNA Replication, cont. DNA replication follows base-pairing rules and is carried out by a group of enzymes: a.Some unwind DNA b.Some break hydrogen bonds between bases c.Some (DNA polymerase) add new bases to make new DNA strands 26

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