DNA replication Flashcards
Describe a nuccleotide and what it contains
a nucleotide is the basic structural unit of a nucleic acids such as dna. nucleotides consist of a pentose sugar, a nitrogenous bas and a phosphate group
describe the structure of DNA
DNA is a nucleic acid/maromolecule made up of subunits called nucleotides. DNA molecules are made uo of two strands that run in opposite directions and thus are said to be antiparallel. Each dna molecule is made up of alternating pentose sugars and phosphate heads that form the sugar-phosphate backbone- bonds that hold them together are called covalent/phosphodiester bonds. the phosphodiester bonds links the 5-carbon of one deoxyribose sugar to the phosphate group from the same nucleotide whch is itself linked to a 3-carbon of the deoxyribose sugar of the next nucleotide strand.Each DNA polynucleotide strand is said to have a 5’ to 3’ end. one strand is known as the 5’ to 3’ end and the other is a 3’ to 5’ end
the nitrogenous bases in the nucleotide project out from the backbone towards the interior of the double stranded dna molecule. the nucleotides contain nitrogenous bases which are as follows: adenine which is complemetary to thymine (or uracil in rna) and cytosine which is complemantary to guanine. these bases are linked together by hydrogen bonds. there are 2 hydrogen bonds between A and T and 3 hydrogen bonds between G and C
list the purine bases and how to tell difference in their structure
adenine and guanine
they are double ringed and adenine has 4 double rings whereas guanine has 3 double rings
list the pyrimdine bases and how to tell the difference in their atructures
thymine, uracil and cytosine
they are single ringed and thymine has a CH3 and cytosine has an NH2 uracil doesn’t have any distince feature that i can use
state the differences between dna and rna
dna is double stranded, contains a deooxyribose sugar, bases are ATGC whereas rna is single stranded, containes a ribose sugar and bases are ATUG
explain semi-conservation of dna
as dna replication occurs the hydrogen bonds between bases are broken and the polynucleotide strand unwinds forming 2 single polynucleotide strands. Each of these strand acts as a tempate for a new dna molecule and this method of conservation is known as semi conservation repliation because the original dna molecule is kept
explain the role of dna polymerase
dna polymerase synthesises new dna dna strands from the template strands by catalysinng condensation reactions between the deoxyribose sugar and the phosphate groups of adjacent nucleotides within the new strands creating the sugar phosphate backbone of the new dna strands, dna polymerae breaks off the two extra phosphate and uses the energy released to create phosphodiester bonds between adjacent nucleotides
