module 2: nucleotides and nucleic acids Flashcards
what is a nucleotide
used to make nucleic acids
a pentose sugar, a nitrogenous base, a phosphate group
e.g. ATP and ADP
what sugar is in DNA
deoxyribose
what are the 4 DNA bases
purine- adenine, guanine
pyrimidine- cytosine, thymie
what is the difference between purine and pyrimidine bases
purine- 2 carbon nitrogen rings
pyrimidine- one carbon nitrogen ring so smaller
what sugar is in RNA
ribose
what bases are in RNA
adenine, guanine, cytosine, uracil
what bond joins nucleotides
phosphodiester
what do 2 polynucleotide strands form
double helix
held together by hydrogen bonds
run anti parallel
how do the bases pair
a to t with 2 hydrogen bonds
g to c with 3 hydrogen bonds
what is used to purify DNA
solution of detergent, salt and distilled water
cells that have been broken up
how does DNA self-replicate
-DNA helicase breaks H bonds between strands causing them to unzip and unwind
-each strand template strands that free floating nucleotides join to by complementary base pairs
-nucleotides joined by DNA polymerase to form sugar-phosphate backbone
-hydrogen bonds from between bases and form double helix
-this is semiconservative replication
what is a gene
sequence of DNA that codes for a polypeptide
what do base sequences code for
amino acids
why is DNA made into mRNA
it is too large to leave the nucleus
3 factors of the genetic code
non over-lapping
degenerate
universal
what is the genetic code
sequence of base triplets in DNA or mRNA that codes for amino acids
describe transcription
1- RNA polymerase unzips and unwinds DNA breaking hydrogen bonds
2- free floating RNA nucleotides line up along template strand and joined by phosphodiester bonds by RNA polymerase creating mRNA
3- orinal 2 strands re-form with hydrogen bonds
4- RNA polymerase reaches stop codon
5- mRNA moves out of nucleus through pore and attaches to ribosome in cytoplasm
describe translation
1- mRNA attaches to ribosome and tRNA carry amino acids to ribosome
2- tRNA molecule has complementary anti-codon to start codon on mRNA to binds
3- second tRNA binds to next codon on mRNA
4-rRNA in ribosome catalyses peptide bond between the two amino acids attached to tRNA, first tRNA moves leaving amino acid behind
5- 3rd tRNA brings amino acid that binds to others and second tRNA moves away
6- process continues until polypeptide chain formed and stop codon reached
