01/23 DNA and RNA structure Flashcards
what is the repeating structural unit of RNA and DNA
a nucleotide
what are the components of a nucleotide
a phosphate group
a pentose sugar
a nitrogenous base
how do the nucleotides of DNA and RNA differ
they differ in their pentose sugars and nitrogenous bases
DNA has deoxyribose, meaning it is missing a hydroxyl group while RNA has ribose, meaning it has a hydroxyl group where the deoxyribose does not
DNA has thymine while RNA has Uracil
why are the 5’ and 3’ carbons important in a nucleotide
the 5’ is where the phosphate head is attached and the 3’ is where the new nucleotide is connected through a phosphodiester bond
what is the 5’ carbon connected to
the 5’ carbon is connected to a phosphate group which is connected to the 3’ of another pentose sugar
what are the purines?
adenine and guanine; double ring nitrogenous bases
what are the pyrimadines
cytosine, thymine, and uracil; single ring nitrogenous bases
what gives DNA it’s negative charge
the phosphate groups
what links nucleotides together
phosphodiester bonds connect the 5’ carbon to the 3’ carbon of another, we always add to the 3’ end and connect it to a 5
what forms the backbone of DNA and where are the bases?
phosphates and sugars form the backbone and the bases project outward from like backbone
who discovered the double helical structure of DNA
James Watson and Francis Crick
who provided the scientfic framework for Watson and Crick’s discovery
Rosalind Franklin (X-ray Diffraction)
Erwin Chargaff (chemical composition)
how did Rosalind franklin discovery the helical structure of DNA
she used X-ray diffraction iwth wet DNA fibers, this revealed a dark pattern that showed a helical, double-stranded formation with 10 base pairs per turn
why was Rosalind franklin not awarded the noble prize for the discovery of DNA
she died after her contributions were discovered, instead they awarded watson and crick with discovering the structure of nucleic acids
how did Chargoff contribute to the discovery of DNA
he helped figure out that A complemented T and that G complemented C
what methodology did Chargoff use to make his discovery
he extracted the chromosomal material and removed protein using a protease, then he hydrolyzed the DNA with a strong acid treatment to remove the bases,
then he used paper chromatography to separate the bases by speed
then he extracted the bands and determined the amounts of each by spectroscopy
what did Chargoff find with his paper chromatography method
the results werent exactly quantitative but he found that the percentage of adenine roughly matched the amount of thymine (30% each) and that thymine roughly matched cytosine
