nucleotides and nucleic acids Flashcards
What are nucleic acids, what are their functions and give some examples.
Nucleic acids are large polymers formed from nucleotides in the cell nuclei which have roles in the storage and transfer of genetic information and the synthesis of polypeptides proteins.
For example DNA and RNA
What does an individual nucleotide consist of?
A nucleotide is made up of a pentose monosaccharide, a phosphate group and a nitrogenous base
How do nucleotides link together?
Nucleotides link together via condensation reactions between a phosphate group (5C) and a hydroxyl group (3C) both found on the pentose sugar.
These are called phosphodiester bonds and forms a long, strong sugar-phosphate backbone.
What are pyrimidines and purines?
Pyrimidines: Smaller bases which contain single carbon ring structures, for example thymine, cytosine and uracil
Purines: Larger bases containing double carbon ring structures such as adenine and guanine.
What is complimentary base pairing?
Refers to how specifically the bases bind together. Adenine and thymine will always form two hydrogen bonds and cytosine and guanine will always form three hydrogen bonds together.
Purines will always bind to a complimentary purine base
This also means there are equal amounts of the base pairing, there will be equal amounts of cytosine = guanine etc..
What is the structure of the double helix?
The DNA is made up of two strands of polynucleotides coiled into a helix known as the DNA double helix.
They are held together by hydrogen bonds between the bases. Each strand has a phosphate group (5”) at one end and group (3’) at the other end.
The two parallel strands are arranged so they run anti parallel.
What is the difference between the structure of DNA and RNA?
DNA has the base thymine binded to adenine instead of uracil
DNA has deoxyribose instead of ribose
DNA is a long molecule which cannot leave the nucleus whereas RNA is much shorter than DNA and can leave the nucleus.
How can DNA be extracted and what precautions must you take?
Grind sample to break cell wall
Mix sample with detergent to break down cell membrane, release cell contents into solution [Detergent will break down cell membrane as it disrupts phospholipid bilayer]
Add salt to break down hydrogen bonds between bases and water molecules
Add protease enzymes to break down proteins associated with DNA in the nuclei [Temperature should be kept constant or enzymes will denature]
Add alcohol on top of sample to allow DNA to precipitate at the top
