Transcript DNA Structure - Cloudfront.net

DNA Structure
How it was discovered
Friedrich Miescher 1869 (Germany)
• Isolated
deoxyribonucleic acid
from nucleus of cells
– Called this white,
slightly acidic
chemical “nuclein”
– Didn’t know it was
genetic material
Frederick Griffith 1928 (England)
• Working on vaccine for pneumonia bacteria
• Discovered that by killing inside of bacteria, it
wouldn’t give disease to mice
Many Scientists 1940
• By this time, many scientists isolated
all of the chemicals found in DNA
– Phosphate (PO4)
– Sugar (deoxyribose)
– Four nitrogen bases (adenine, thymine,
cytosine, guanine)
• Now called “deoxyribose nucleic acid”
or DNA
Oswald Avery 1944 (USA)
• Worked with bacteria that
causes pneumonia
• Used DNA-destroying
enzyme to kill DNA inside
bacteria before inserting it
into animal
– Animal didn’t get
pneumonia
– DNA is genetic material
Structure
• … was still unknown
– How did the phosphate, deoxyribose, and
4 bases fit together?
• Knew that amount of adenine ALWAYS
equaled amount of thymine
• Knew that amount of cytosine
ALWAYS equaled amount of guanine
Rosalind Franklin 1951 (England)
• Worked on x-ray crystal diffraction
photographs (how light bounced off
crystals) of DNA structure
• Worked in same area as Maurice
Wilkins who tended to treat her as
his assistant
– Wilkins was working on separate
DNA projects
James Watson and Francis Crick, 1953
(England)
• Wilkins showed Watson Franklin’s x-ray
photograph
• Watson said "The instant I saw the picture, my
mouth fell open and my pulse began to race.”
– Showed photo to Crick who
instantly began work with
Watson on DNA model using
balls and sticks
• 1953 scientific paper
published called “A Structure
for Deoxyribose Nucleic Acid’
Nobel Prize 1962
• Maurice Wilkins, Francis Crick, and James Watson
received Nobel Prizes for Physiology or Medicine for
work on DNA structure
– Rosalind Franklin was not honored
– She died 4 yrs earlier in 1958 at age 37 of ovarian
cancer