12.2 Flashcards
What is DNA?
DNA is a nucleic acid made up of nucleotides joined into
long strands or chains by covalent bonds.
What is nucleotide made up of?
Nucleotide is made up of three components:
a base, a deoxyribose sugar, and a phosphate group
What are are four different nitrogenous bases found in
DNA nucleotides:
adenine, guanine, cytosine, and
thymine
What’s Chargaff’s rule
the percentages of adenine [A]
and thymine [T] bases are almost equal in any sample of DNA. The
same thing is true for the other two nucleotides, guanine [G] and
cytosine [C].
How did Rosalind Franklin study the structure of DNA
Rosalind Franklin used a technique called X-ray diffraction
to study the structure of DNA
What are her three clues
1 DNA is a helix. 2. Likely two strands to the molecule 3. Nitrogenous bases near the center of the molecule
What did Watson and crick Say
Watson and crick said that the DNA is a double helix
How is the arrangement of strands described as?
The two strands in a DNA molecule run in opposite
directions. This arrangement of strands is described as
“antiparallel.
What holds bases together?
Hydrogen bonds
The two strands of DNA are held together by hydrogen
bonds between the nitrogenous bases adenine and …..
and between guanine and…..
Thymine, cytosine
Watson and Crick had realized that hydrogen bonds would
form only between A and T and between C and G. This fit
between bases is called
Base pairing
