DNA
description
Transcript of DNA
![Page 1: DNA](https://reader036.fdocuments.us/reader036/viewer/2022062521/56813e6a550346895da87e6a/html5/thumbnails/1.jpg)
DNADNA
HistoryStructureReplication
![Page 2: DNA](https://reader036.fdocuments.us/reader036/viewer/2022062521/56813e6a550346895da87e6a/html5/thumbnails/2.jpg)
History of DNAHistory of DNA
Scientists thought protein was the heredity material
Several Scientists disproved this and proved it was DNA:
![Page 3: DNA](https://reader036.fdocuments.us/reader036/viewer/2022062521/56813e6a550346895da87e6a/html5/thumbnails/3.jpg)
GriffithGriffith Worked with virulent S and nonvirulent R strain of
pneumococcus bacteria Made the harmless R strain transform into S strain
when it took in DNA from the killed S strain.
![Page 4: DNA](https://reader036.fdocuments.us/reader036/viewer/2022062521/56813e6a550346895da87e6a/html5/thumbnails/4.jpg)
Hershey & ChaseHershey & Chase
Worked with radioactively traced bacteriophages (viruses that attack bacteria).
Further proof that DNA was the cell’s genetic material.Radioactive 32P was injected into bacteria!
![Page 5: DNA](https://reader036.fdocuments.us/reader036/viewer/2022062521/56813e6a550346895da87e6a/html5/thumbnails/5.jpg)
ChargaffChargaff
Developed the base pairing rule by comparing the amounts of A, T, C, G in the cell.
Nucleotide pairing:– Adenine Thymine– Guanine Cytosine
![Page 6: DNA](https://reader036.fdocuments.us/reader036/viewer/2022062521/56813e6a550346895da87e6a/html5/thumbnails/6.jpg)
FranklinFranklin
Took x-ray photographs of DNA
Determined double-helix structure
![Page 7: DNA](https://reader036.fdocuments.us/reader036/viewer/2022062521/56813e6a550346895da87e6a/html5/thumbnails/7.jpg)
Watson & CrickWatson & Crick
Watson and Crick used Franklin’s x-rays, Chargraff’s rule and developed their model of the DNA molecule (for which they won a Nobel Prize).
![Page 8: DNA](https://reader036.fdocuments.us/reader036/viewer/2022062521/56813e6a550346895da87e6a/html5/thumbnails/8.jpg)
Structure of DNAStructure of DNA
![Page 9: DNA](https://reader036.fdocuments.us/reader036/viewer/2022062521/56813e6a550346895da87e6a/html5/thumbnails/9.jpg)
Shape of DNAShape of DNA
Double stranded, twisted helix, called a double helix
Shape similar to a twisted ladder
![Page 10: DNA](https://reader036.fdocuments.us/reader036/viewer/2022062521/56813e6a550346895da87e6a/html5/thumbnails/10.jpg)
Nucleotide MonomersNucleotide Monomers
DNA Nucleotide is the basic unit (monomer)
Made of:Sugar – DeoxyribosePhosphate group (PO4)Base – A T C G (Adenine, Thymine,
Cytosine, Guanine)
![Page 11: DNA](https://reader036.fdocuments.us/reader036/viewer/2022062521/56813e6a550346895da87e6a/html5/thumbnails/11.jpg)
DNA NucleotideDNA Nucleotide((glue picture provided in NB)glue picture provided in NB)
N
OO=P-O O
PhosphatePhosphate GroupGroup
Nitrogenous baseNitrogenous base (A, G, C, or T)(A, G, C, or T)
CH2
O
C1C4
C3 C2
5
SugarSugar(deoxyribose)(deoxyribose)
![Page 12: DNA](https://reader036.fdocuments.us/reader036/viewer/2022062521/56813e6a550346895da87e6a/html5/thumbnails/12.jpg)
Polymer StructurePolymer Structure
Sides made of phosphate group and deoxyribose sugar
Center (rungs) made of nitrogen bases bonded by hydrogen bonds (A = T and C = G)
![Page 13: DNA](https://reader036.fdocuments.us/reader036/viewer/2022062521/56813e6a550346895da87e6a/html5/thumbnails/13.jpg)
Direction of NucleotidesDirection of NucleotidesEach carbon in the sugar is given a
number 1’ – 5’
Sides are antiparallel – one side goes 5’ to 3’ and the other 3’ to 5’
This determines the direction that it is “read” by enzymes
![Page 14: DNA](https://reader036.fdocuments.us/reader036/viewer/2022062521/56813e6a550346895da87e6a/html5/thumbnails/14.jpg)
DNA StructureDNA Structure(glue picture provided in NB)(glue picture provided in NB)
P
P
P
O
O
O
1
23
4
5
5
3
3
5
P
P
PO
O
O
1
2 3
4
5
5
3
5
3
G C
T A
![Page 15: DNA](https://reader036.fdocuments.us/reader036/viewer/2022062521/56813e6a550346895da87e6a/html5/thumbnails/15.jpg)
Location of DNALocation of DNA
DNA is a large (macro) molecule, and stays in the nucleus
![Page 16: DNA](https://reader036.fdocuments.us/reader036/viewer/2022062521/56813e6a550346895da87e6a/html5/thumbnails/16.jpg)
DNA ReplicationDNA Replication
![Page 17: DNA](https://reader036.fdocuments.us/reader036/viewer/2022062521/56813e6a550346895da87e6a/html5/thumbnails/17.jpg)
S Phase of Cell CycleS Phase of Cell Cycle
DNA must be copied before the cell can divide
Occurs during the synthesis (S) part of cell cycle (before mitosis). Mitosis
-prophase-metaphase-anaphase-telophase
G1 G2
Sphase
interphase
![Page 18: DNA](https://reader036.fdocuments.us/reader036/viewer/2022062521/56813e6a550346895da87e6a/html5/thumbnails/18.jpg)
Helicase enzymeHelicase enzyme DNA unwinds and unzips with help of DNA helicases These enzymes break the hydrogen bonds between
base pairs. This point is called the replication fork.
ReplicationReplicationForkFork
Parental DNA MoleculeParental DNA Molecule
3’
5’
3’
5’
![Page 19: DNA](https://reader036.fdocuments.us/reader036/viewer/2022062521/56813e6a550346895da87e6a/html5/thumbnails/19.jpg)
Polymerase EnzymePolymerase Enzyme
DNA polymerase moves in new nucleotides Can only add to 3’ end of nucleotide Follows the base-pairing rule Two identical DNA strands are formed
RNARNAPrimerPrimerDNA PolymeraseDNA PolymeraseNucleotideNucleotide
5’
5’ 3’
Direction of ReplicationDirection of Replication
![Page 20: DNA](https://reader036.fdocuments.us/reader036/viewer/2022062521/56813e6a550346895da87e6a/html5/thumbnails/20.jpg)
Proofreading enzymesProofreading enzymes
Other enzymes “proofread” the replicated strand looking for errors (mutations).
Incorrect nucleotides are removed and replaced