Chemistry Of Nucleic Acids (week 11) Flashcards
What are the monomers hat make up DNA?
Nucleotides -
Nitrogenous base (4 types)
Phosphate group
Ribose sugar
What bonds join the nitrogenous bases to the ribose sugar?
Glycosidic bonds
What are the nitrogenous bases?
Purines -
Adenine (NH2 group)
Guanine (NH2 group and dbl bond O)
Pyrimidines -
Cytosine (NH2)
Thymine (CH3 - non-polar - and dbl bond O)
How do phosphates attach to the 5’ carbon?
Ester link
Why is DNA dissolved in water considered to be an acid?
Phosphate groups on the outside of the structure can ionise
Why does DNA have a major and minor group (grooves)?
To allow access for proteins to base pairs.
How is human DNA packaged?
It is wrapped around hisome octamers - 4 histones in each octamer, DNA is wrapped around twice
DNA gyrase role?
Topoisomerase that interchanges DNA coiling between relaxed and supercoiled
How is bacterial DNA packaged?
Supercoiling circles of DNA, DNA gyrase can change this to relaxed for replication
How do you differentiate between single and double stranded DNA?
UV absorbency at 260nm
Single = more
Double = less
How do you measure DNA hyperchronism (denaturation)?
Using UV at 260nm
An increase in dbl stranded DNA melting temp can be caused by what?
More guanine and cytosine base pairs due to there being more hydrogen bonds.
What do nucleases do to DNA?
Cleave DNA
Exo - cut ends
Endo - cut within, some random and some are sequence specific
What are palindromic sequences?
Sticky ends
What is the role of restriction endonuclease?
Protective immune role.
Cleaves foreign DNA
Recognises palindrome repeats
