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1. What structure carries genetic information from generation to
generation?2. Which organelle is this
structure located in? 3. How long do you think it has taken to discover DNA and its structure? Do you think one person is responsible for the
discovery?
DNA is the GENETIC or HEREDITARY material.
In other words, DNA is what gets “passed down” to future
generations that causes us to have many of the traits we have.
Gregor Mendel
• “Father of Genetics” (1822-1884)
• Famous experiments with pea plants that explained patterns of inheritance
• Two “units” of information- one from each parent
• First scientist to acknowledge material for heredity
Frederick Griffith 1928
Fred was trying to find a vaccine against pneumonia, but instead made a breakthrough in world of heredity.
Frederick experimented with pneumonia in mice and found that a hereditary material caused pneumonia.
Determined which molecules in cells caused pneumonia to occur.
He separated all organic compounds inside of the cells and found only the DNA caused
the disease.
*******Conclusion: DNA must be the hereditary material
Oswald Avery, 1944
Alfred Hershey &Martha Chase,1952
• Skeptical of other scientists’ experiments
• Wanted to be sure DNA was hereditary material
Rosalind Franklin,1952
• Studied structure of many microscopic viruses and cellular structures
• Researched DNA – used X-RAY Diffraction to show shape of DNA= helical w/ 2 strands.
• Rosalind’s lab work was stolen
Watson and Crick’s model of DNA was a DOUBLE HELIX,
in which two strands were wound around each other.
The sides of the DNA “ladder” are
made ofSUGARS and
PHOSPHATES.
So, DNA is said to have a
SUGAR-PHOSPHATE BACKBONE.
Erwin Chargaff,in the early
1900s,discovered that
certain chemicals in all DNA seemed to be present in almost EQUAL
amounts.
ADENINE and THYMINE were
always present in equal amounts.
GUANINE and CYTOSINE were
always present in equal amounts.
THE BASE PAIRING RULE:Adenine [A] always pairs with
Thymine [T]Guanine [G] always pairs with
Cytosine [C]
THE BIG PICTUREDNA is composed of a deoxyribose
sugars, phosphates, and paired nitrogenous bases...
Sugar-phosphate backbone
Nitrogenous base pairs