the genetic code
DESCRIPTION
the Genetic Code. Shown as mRNA 5′ → 3′ 64 codons Redundant One “start” codon: AUG Three “stop” codons: UAG, UAA, UGA (don’t encode amino acids). template strand. mRNA. CUACGAGGAGGUGAAGCGAUGCCCCGUAGCCGAUAGUAGC. 3’. 5’. the Genetic Code. - PowerPoint PPT PresentationTRANSCRIPT
Shown as mRNA 5 ′ → 3′ 64 codons Redundant One “start” codon: AUG Three “stop” codons: UAG,
UAA, UGA (don’t encode amino acids)
the Genetic Code
templatestrand
For each gene, one DNA strand is transcribed Template strand “read” mRNA complementary to template
the Genetic Code
CTACGAGGAGGTGAAGCGATGCCCCGTAGCCGATAGTAGC 3’5’DNA GATGCTCCTCCACTTCGCTACGGGGCATCGGCTATCATCG 5’3’
CUACGAGGAGGUGAAGCGAUGCCCCGUAGCCGAUAGUAGC 3’5’ mRNA
Non-template strand looks like RNA (except T’s)also called the sense strand
non-templatestrand
the Genetic Code
CTACGAGGAGGTGAAGCGATGCCCCGTAGCCGATAGTAGC 3’5’DNA GATGCTCCTCCACTTCGCTACGGGGCATCGGCTATCATCG 5’3’
CUACGAGGAGGUGAAGCGAUGCCCCGUAGCCGAUAGUAGC 3’5’ mRNA
start codon:AUG
stop codon:UAG, UGA or UAA
Ribosome starts at 5’ end of mRNA (in eukaryotes) Protein synthesis begins at start codon, ends at stop codon
the Genetic Code
CUACGAGGAGGUGAAGCGAUGCCCCGUAGCCGAUAGUAGC 3’5’ mRNA
codons
this stop codonis not “in-frame”so it’s ignored!
MetProArgSerArg protein
Change in nucleotide sequence of DNA Caused by:
DNA polymerase mistake Chemical change within cell UV light or other radiation Mutagenic chemical
Mutation
Effects of mutations
ACGATCCTATGCCCCGCAGCCGATAGTCTCATTTGCTAGGATACGGGGCGTCGGCTATCAGAGTAA
DNA5’ 3’
5’3’
ACGAUCCUAUGCCCCGCAGCCGAUAGUCUCAUURNA
5’ 3’
Effects of mutations
ACGATCCTATGCCCCGCAGCCGATAGTCTCATTTGCTAGGATACGGGGCGTCGGCTATCAGAGTAA
DNA5’ 3’
5’3’
ACGAUCCUAUGCCCCGCAGCCGAUAGUCUCAUURNA
5’ 3’
MetProArgSerArg
Missense: single amino-acid changeEffects of mutations
ACGATCCTATGCCCCGCCGCCGATAGTCTCATTTGCTAGGATACGGGGCGGCGGCTATCAGAGTAA
DNA5’ 3’
5’3’
ACGAUCCUAUGCCCCGCCGCCGAUAGUCUCAUURNA
5’ 3’
MetProArg???Arg
Could this change have an effect on protein function?Could it affect the whole organism?
Missense: single amino-acid changeEffects of mutations
ACGATCCTATGCCCCGCCGCCGATAGTCTCATTTGCTAGGATACGGGGCGGCGGCTATCAGAGTAA
DNA5’ 3’
5’3’
ACGAUCCUAUGCCCCGCCGCCGAUAGUCUCAUURNA
5’ 3’
MetProArgArgArg
Could this change have an effect on protein function?Could it affect the whole organism?
Missense: single amino-acid changeEffects of mutations
ATGTCTATCCAGGTTGAGCATCCTGCTGGTGGTTACAAGAAACTGTTTGAAACTGTGGAGGAACTGTCCTCGCCGCTCACAGCTCATGTAACAGGCAGGATCCCCCTCTGGCTCACCGGCAGTCTCCTTCGATGTGGGCCAGGACTCTTTGAAGTTGGATCTGAGCCATTTTACCACCTGTTTGATGGGCAAGCCCTCCTGCACAAGTT…
Wild-type RPE65:
ATGTCTATCCAGGTTGAGCATCCTGCTGGTGGTTACAAGAAACTGTTTGAAACTGTGGAGGAACTGTCCTCGCCGCTCACAGCTCATGTAACAGGCAGGATCCCCCTCTGGCTCACCAGCAGTCTCCTTCGATGTGGGCCAGGACTCTTTGAAGTTGGATCTGAGCCATTTTACCACCTGTTTGATGGGCAAGCCCTCCTGCACAAGTT…
Mutant RPE65:
MetSerIleGlnValGluHisProAlaGlyGlyTyrLysLysLeuPheGluThrValGluGluLeuSerSerProLeuThrAlaHisValThrGlyArgIleProLeuTrpLeuThrGlySerLeuLeuArgCysGlyProGlyLeuPheGluValGlySerGluProPheTyrHisLeuPheAspGlyGlnAlaLeuLeuHisLysPheAspPheLysGlu…
MetSerIleGlnValGluHisProAlaGlyGlyTyrLysLysLeuPheGluThrValGluGluLeuSerSerProLeuThrAlaHisValThrGlyArgIleProLeuTrpLeuThrSerSerLeuLeuArgCysGlyProGlyLeuPheGluValGlySerGluProPheTyrHisLeuPheAspGlyGlnAlaLeuLeuHisLysPheAspPheLysGlu…
Missense: single amino-acid changeEffects of mutations
ATGGTGCATCTGACTCCTGAGGAG…MetValHisLeuThrProGluGlu
GTG Val
Hemoglobin → sickle-cell anemia:
Nonsense: creates stop codonEffects of mutations
AUGCCCCGCAGCCGAUAGMetProArgSerArg
AUGCCCCGCAGCUGAUAGMetProArgSerXXX
Deletion: creates frameshift, changes all following aa’sEffects of mutations
AUGCCCCGCAGCCGAUAGMetProArgSerArg
AUGCCCGCAGCUGAUAGMetProAlaAlaAsp…
Insertion: creates frameshift, changes all following aa’sEffects of mutations
AUGCCCCGCAGCCGAUAGMetProArgSerArg
AUGGCCCCGCAGCUGAUAGMetAlaProGlnProIle…
Silent: DNA changes, but protein doesn’tEffects of mutations
AUGCCCCGCAGCCGAUAGMetProArgSerArg
AUGCCCCGCAGUCGAUAGMetProArgSerArg