nucleotides are the monomers from which nucleic acids like DNA and RNA are formed
nucleic acids contain nitrogenous bases , phosphate group and a pentose sugar
the nitrogenous bases are categorised by their ring structures and organised into purines and pyrimidines
purines have a 2 carbon ring structure and are adenine and guanine
pyrimidines have a single carbon ring structure and are cytosine, thymine and uracil
guanine is always paired with cytosine
adenine is always paired with thymine or uracil
uracil is only found in RNA
deoxyribose sugar is found in DNA
ribose sugar in RNA
purines and pyrimidines bases are always opposite each other in dna maintaining order
both RNA and DNA undergo condensation reaction forming phosphodiester bonds
the phosphodiester bond between adjacent nucleotides form the polymer polynucluotides
phosphodiester bonds are very strong covalent bonds
DNA codes for the sequence of amino acids in primary structure of protein which determines the 3d shape of tertiary structure
polymer forms a double helix made of two antiparelel strands joined together by hydrogen bonds
DNA has a stable structure due to the phosphodiester bonds that form between nucleotides
weak hydrogen bonds between bases makes it easier for strands to separate for DNA replication
DNA is a large molecule so can carry a lot of information
DNA can be extracted out of cell using the method of precipitation
RNA is single-stranded, whereas DNA is double-stranded.
three types of RNA are tRNArRNA and mRNA
rRNA forms part of the ribosome which is where proteins are made
mRNA leaves the nucleus via nuclear pores and carries genetic code to ribosomes in cytoplasm
mRNA is single stranded and every 3 bases in the sequence codes for a specific amino acid these are called codons
tRNA has an anticodon that matches with the codon on mRNA so it brings the correct amino acid to the ribosome
tRNA is single stranded but folds into clove leaf like structure held in place by hydrogen bonds
tRNA carries specific amino acids to ribosomes this is determined by the 3 bases on tRNA called anticodons
DNA replication is described as semi conservative as one single strand of DNA is conserved and one entire new strand is created from new nucleotides
copying errors can occur but they are random and they result in the change in DNA sequence this is called a mutation
DNA replication occurs in s phase in interphase of cell cycle
the genetic code has 3 features which are that it is degenerateuniversal and nonoverlapping
degenerate means that the amino acids are coded for by more that one triplet of bases of DNA
the genetic code being degenerate is an advantage as even if a mutation occurs changing a base in triplets still codes for the same amino acid meaning no impact on final sequence of amino acids
universal means the triplet of bases codes for same amino acids in all organisms
the genetic code being universal is an advantage as it means we are able to remove a human gene and insert into the plasmids of a bacterium
on overlapping means each base in a gene is only part of one triplet base that codes for one amino acids
the genetic code being non overlapping is an advanatage as if there was a mutation the mutation will only affect one codon
protein synthesis is when proteins are being created on ribosomes on RER
protein synthesis occurs in two stages translation and transcription