Nucleic acids Flashcards
what is a nucleotide made from
a pentose sugar, a nitrogenous base, a phosphate group
what are the differences between RNA and DNA nucleotides
the pentose sugar in DNA is deoxyribose whereas in RNA it is ribose, also in RNA instead of thymine there is uracil, and RNA is made of a single polynucleotide chain and DNA is made of two
what does a purine contain
two carbon-nitrogen rings joined together, A and G
what does a pyrimidine base contain
one carbon nitrogen ring, the base is smaller than a purine base, C, T and U
how do you join nucleotides and what does this form
join the phosphate of one to the sugar of another via a condensation reaction which forms a phosphodiester bond, forms a polynucleotide which can be broken by hydrolysis
what bonds the bases together
hydrogen bonds
what does ATP do
provides energy for chemical reactions in the cell,
where does ATP come from
synthesised from ADP
how to do you purify DNA
using a precipitation reaction
what does DNA helicase do in self replication
breaks the hydrogen bonds between the polynucleotide DNA strands
what does DNA polymerase do in self replication
joins the nucleotides of new strands
why is the copying referred to as semi conservative
because half of the strands in each new DNA molecule are from the original piece of DNA
what is a mutation
any change to the DNA base sequence
what are the three main types of RNA
mRNA, tRNA and rRNA
what is mRNA
made in the nucleus, carries the genetic code from the DNA in the nucleus to the cytoplasm, where its used to make a protein during translation
what is tRNA
found in the cytoplasm, has a amino acid binding site, and a sequence of three bases called an anticodon, carries the amino acids that are used to make proteins to the ribosomes during translation
what is rRNA
forms the two subunits in a ribosome which moves along the mRNA strand during protein synthesis, rRNA in the ribosome helps to catalyse the formation of peptide bonds between the amino acids
describe the kiwi experiment
mix sample (kiwi) with detergent, which breaks down the cell membrane and releases the contents, add salt to break down the hydrogen bonds between DNA and water molecule, add protease enzyme which breaks down the proteins associated with the DNA in the nuclei, add alcohol to make the DNA precipitate out of the solution
what are the first steps of transcription
RNA polymerase attaches to the DNA double helix, the hydrogen bonds between the two DNA strands in the gene break and the molecule uncoils. on of the strands is used as a template to make an mRNA copy
what is are the second steps transcription
RNA polymerase lines up free RNA nucleotides alongside the template strand, complementary pairing makes it a complementary copy apart from thymine which is uracil, then the bases join together and form an mRNA molecule
what are the fourth steps of transcription
RNA polymerase moves along separating the strands and assembling the mRNA strand, once it passes by them the strands coil back into a double helix
what are the last steps of transcription
once the RNA polymerase reaches a stop codon it detaches from the DNA, mRNA moves out the nucleus through a nuclear pore and attaches to a ribosome in the cytoplasm
what are the first steps of transcription
tRNA carry amino acids to the ribosome, the starting tRNA has a anticodon thats complementary to the start codon, then the next and so on
what are the second steps of transcription
rRNA in the ribosome catalyses the formation of a peptide bond between the two amino acids attached to the tRNA molecule and the tRNA molecule moves away and this forms a polypeptide chain
