DNA and RNA composition and structure Flashcards
Nucleic acids are biomolecules what does this mean?
They are used to store, transfer and express genetic information
Nucleic acids are polymetric what does this mean?
They are made up of small units (molecules)
Give two examples of nucleic acids?
* DNA- instructions that an organism needs to develop, live, and reproduce
* RNA- translates information from DNA into proteins (and many other functions)
History of DNA
*** 1869- **Friedrich Miescher discovered a microscopic substance isolated from the nuclei of white blood cells and called it ‘nuclein’
* 1953- James Watson, Francis Crick, Maurice Wilkins, and Rosalind Franklin proposed model of the structure of DNA- a double helix
* 1962- Watson, Crick and Wilkins were awarded the Nobel Prize in Medicine “for their discoveries concerning the molecular structure of nucleic acids and its significance for information transferrin living material”
What is the structure of DNA comprised of?
Tell me about the structure of the sugar group of DNA
-
Deoxyribose in DNA
* Pentose- monosaccharide (simple sugar) with a 5-carbon ring - the carbon atoms of the five-carbon sugar are numbered clockwise from the oxygen as 1’, 2’, 3’, 4’ and 5’
o 1’ is read as one prime
o Important for directionality
Tell me about the phosphate group of DNA
- Forms an ester bond with 5’-OH group of the deoxyribose sugar
- A functional group containing one atom of phosphorous covalently bound to four oxygen atoms (3 with a single bond and one which a double bond)
- Allows the formation of the sugar-phosphate
“backbone” - Makes DNA molecules **negatively charged **
What are the nitrogenous bases (nucleobases) in DNA?
How are they connected?
What determines the genetic code?
The order of nucleobases determines the DNAs instructions
What are the purines and pyrimidines and how many rings does each structure have?
what is the nomenclature of the following:
Sugar + Base =
Phosphate + Sugar + Base=
3x Phosphate + Sugar + Base=
What is the primary structureof DNA?
*** Primary structure **of DNA
* Phosphodiester bond forms between the 5’ carbon of one nucleotide and the 3’ carbon of the next to form a strand of nucleotides
* these sugar-phosphate groups line up to form the “backbone” for each strand of DNA
* the nucleotide bases stick out from this backbone
Tell me about the** secondary structure** of DNA
- Hydrogen bonding between bases
o A=T (2 H bonds) **
o G=C (3 H bonds)**
* Chargaff’s rule- complementarity of bases result in”
o 1:1 ratio between purines and pyrimidines
o Amount of adenine equal to thymine
o Amount of guanine equal to cytosine - Along with the stacking interactions between the nucleotides this determines the secondary structure of DNA
What orientation are the complimentary polynucleotide strands?
Oriented in opposite directions or antiparallel
One strand will have the 5’ carbon of the sugar in the “upward” positions, whereas the other strand will have the 3’ carbon in the upward position
Why is the diameter of the DNA double helix always constant?
As a purine (two rings) always pairs with a pyrimidine (one ring)- the combined length of the base pairs is always equal
The tertiary arrangement of the DNAs double helix in space can exist in what different forms?
How can these forms vary?
A-DNA
B-DNA
Z-DNA
The double helix structure in these forms can vary in:
o Handedness- right or left
o Length of the helix turn
o Number of bp per turn
o Size of major and minor grooves (thought to be binding sites for proteins)
What is the structure of RNA?
- Like DNA, RNA is a polymer of nucleotides
- Each nucleotide contains the same components as DNA, a phosphate group, a sugar group, and a nitrogenous base
- In RNA, the five-carbon sugar is ribose and not deoxyribose- has an additional hydroxyl group at 2’ carbon
- Does not contain thymine, this is replaced by uracil
