chp. 16 Flashcards
claims that each gene contains the information needed to make an enzyme
One gene one enzyme-
N. crassa cells exposed to radiation, examine mutant cells, found mutants that could make specific compounds, demonstrated the inability to synthesize pyridoxine was due to a defect in a single gene and inability to synthesize other molecules was due to defects n other genes.
Beadle and Tatum studies
central dogma
DNA (information storage((→transcription)mRNA(information carrier) ( → translation)proteins(active cell machinery)
Rules that specify the relationship between a sequence of nucleotides in DNA or RNA and the sequence of amino acids in a protein
genetic code
Genes with three deletion mutations were able to produce a functioning
protein
all amino acids except for Met and tryptophan are coded by more than one codon.
redundant
single codon never codes more than one amino acid.
Unambiguous
once the ribosome locks onto the first codon it then reads each separate codon one after another.
Non-overlapping
with a few minor exceptions, all codons specify the same amino acids in all organisms.
Nearly universal
when several codons specify the same amino acid, the first two bases in those codons are almost always identical.
Conservative
single base change. Results in coat color change in populations of mice.
Point mutation
does not change amino acid sequence of the gene product.
Silent mutation
different color coats.
Missense mutation
throws sequence of codons out of register and alters the meaning of all subsequent codons
Frame shift mutation
causes early termination of the poly-peptide chain and often results in a non-functional protein.
Nonsense mutation
