DNA Flashcards
What is DNA? Draw it.
• Polymer containing similar monomers linked by covalent bonds. • A monomer contains: o Deoxyribose (5C) o Basic group at C 1 o Phosphate residue. .
What are The bases? Purine/pyramidine?
o Adenine – Purine – (dAMP) deoxyadenosine 5’-monophosphate.
o Guanine - Purine – (dGMP) deoxyguanosine 5’- monophosphate.
o Cytosine - Pyrimidine – (dCMP) deoxycytidine 5’-monophophate.
o Thymine – Pyrimidine – (dTMP) deoxythymidine 5’-monophosphate.
o Very rarely in 1:1:1:1 ratio (humans AT higher than CG)
..
What Direction is DNA read?
o Phosphate residue links each monomer between 3’hydroxyl of one with 5’hydroxyl of the next. Giving the chain a sense of direction.
What links 2 nucleotides in DNA?
o The link is a phosphodiester bond.
Where is the acid in the nucleic acid?
o The acidity of the phosphate group = nucleic acid.
Describe the Structure of DNA, including the planes, what determines this structure?
o Bases are on the inside and the sugar and phosphate residues are on the outside.
o Sugar-phosphate back bone is very regular.
o The plane of the bases is almost perpendicular to the backbone.
o The planes of the sugar is at right angles to the bases.
o Structural stability due to Van de Walls between bases on same strand and hydrogen bonds between opposing bases.
Describe Base pairing, what bonds?
o 2 chains interact vi hydrogen binds between pairs of bases.
o A-T C-G therefore these bases are always found in equal amounts.
o C-1’ are found the same distance apart but don’t lie directly opposite each other.
What forms the grooves?
o Therefore 2 backbones are not equally spaced along the helix = major and minor groove.
o Sequence of bases along the chain is not restricted.
What is DNA Melting? What can make this higher?
o 2dry structure of DNA = v. stable – however “melts” if heated. (65-80celcius)
o if cooled slowly it repairs (hybridises) but if cooled rapidly bases are unable to find complementary pair.
o If there is a high G-C count – 3 h-bonds have to be broken therefore higher temp for melting needed.
What are the Dimensions of DNA? Helix diameter? Adjacent bases? When does helical structure repeat? Draw a DNA with measurements on it (this is a good thing to add even if they don’t ask for the numbers)..
o Helix diameter – 2nm
o Adjacent bases – 0.34nm + 36 rotation.
o Helical structure repeats after 10 residues = 3.4nm..
How big the human genome?
o Genome huge – human =3x109bp.
How is DNA packaged?
o DNA folds into Chromatin 30nm – this is regulated by altering histone tails via gene activation. (epigenetics = inherited)
o Packaged into chromatid = 700nm replicated chromosome = 1400nm.
