Molecular Biochemistry Flashcards
Sickle Cell disease mutations in DNA
Missense - Nucleotide substitution resulting in changed amino acid
Silent Mutations in DNA
Nucleotide substtions but codes for the same amino acid; often base changed in 3rd position of codon
Nonsense Mutations in DNA
nucleotide substition in early stop codon. Stop the nonsense!
Duchenne muscular atrophy DNA mutation type
Frameshift - deletion or insertion of a number of nucleotides not divisible by 3, resulting in mistreading of all nucleotides downstream, usually resulting in a truncated, nonfunctional protein
Order of severity of DNA mutations
Silent «_space;missense < nonsense < frameshift
Why is nucleotide exicision repair defective in xeroderma pigmentosum?
Prevents repair of pyrimidine dinners because of ultraviolet light exposure
Nucleotide excision repair
specific endonucleases releasethe oligonucleotide-containing damage bases; DNA polymerase and ligase fill and reseak the gap, respecitively. Repairs bulky helix-distorting lesions
Base excision repair
Base-specfic glycosylase recognizes altered base and creates AP sites (apurinic/apyrimidinic). One or more nucleotides are removed by AP-endonuclease, which cleaves the 5’ end. Lyase cleaves the 3’ end. DNA polymerase-betafills the gap and DNA ligase seals it
Nonhomologous end joining - double strand
Brings tighter 2 ends of DNA fragments to repair double-stranded breaks
Chain Terminator
3’ OH
DNA/RNA synthesis direction
5’ to 3’
Triphosphate bone end
5’
mRNA start codons
AUG (rarely GUG)
Eukaryotes code for…
methionine
Prokaryotes code for…
formylmethionine (f-met)
