DNA structure and chromosomes Flashcards
what is the function of DNA?
transmits all the cell’s genetic information.
every time a cell divides, it must pass on an exact copy of all its DNA to each daughter
describe the structure of DNA
DNA is made up of multiple nucleotides, linked together by a sugar-phosphate backbone.
the 2 polynucleotides run anti-parallel to each other, held by hydrogen bonds between the bases of different strands. the two strands are wound up to make a double helix
what are polynucleotides?
polynucleotides are formed via phosphodiester bonds.
one nucleotide attaches to another covalently by phosphodiester bonds, between the OH group of one sugar and the phosphate group of the next sugar.
how do DNA strands pair up?
dan strands pair up by complementary base pairing.
2 H bonds between A and T
3 H bonds between C and G
what are major and minor grooves in the DNA helix?
Major grooves occur where the backbones are far apart
minor grooves occur where they are close together.
what are major and minor grooves in the DNA helix?
Major grooves occur where the backbones are far apart
minor grooves occur where they are close together.
prokaryotic chromosomes and how do we package them?
most prokaryotic chromosomes contain one double-stranded circular chromosome.
they are packaged by forming loops and being supercoiled.
eukaryotic chromosomes and how do we package them?
proteins called histones are needed to bind and fold the DNA into coils and loops.
what are histones?
histones are highly conserved, small, basic proteins with a positive charge that bind to the negatively charged DNA.
DNA packaging: how is DNA packed up to fit into the nucleus of every cell.
first DNA is wrapped around a special protein molecules called hsitones.
the combined loop of DNA and proteins is called nucleosome
next the nucleosome are packaged into a thread ‘beads on the string’
the end result is called a chromatin.
