structures and bonding in DNA

how is a cell controlled by genes

nucleus contains DNA, DNA contains genes to provide info to make proteins

DNA cannot leave nucleus, mRNA is a copied section of DNA and leaves the nucleus and carries genetic information to the ribosomes

sequence of nucleotides in the mRNA used to make proteins at the ribosome

nucleotide is a group of molecules called…

made of monomers called…

nucleic acids

mononucleotide

nucleotide consists of…

phosphate group

pentose sugar (deoxyribose)

nitrogenous base - adenine, thymine, guanine or cytosine

polynucleotide formation

many nucleotides join together via condensation reactions

between phosphate group of the 5’ carbon of one nucleotide

and the hydroxyl group (on a pentose sugar) of the 3’ carbon of another nucleotide

forms phosphodiester bonds

forming sugar phosphate backbone

purine bases

have an N in their names

adenine

guanine

purines are large and double-ringed

pyrimidine bases

have a Y in their names

cytosine and thymine

are smaller and single-ringed

complementary base pairings + hydrogen bonds

adenine and thymine - 2 hydrogen bonds

cytosine and guanine - 3 hydrogen bonds

structure of DNA

double-helix structure

two strands of polynucleotides

very long and coiled up - can fit into the small space of the nucleus

two strands run in anti-parallel direction