Download lecture 6 genetic languages and mutations_RECAP

Genetic
Languagesand
Mutations
YouShouldBeAbleTo…
1. AnalyzeapieceofDNAanddeterminethe
aminoacidsequencethatisultimately
produced.
2. Compareandcontrastthreedifferenttypes
ofmutation,andthethreepotential
implicationsofmutation.
3. Describethedifferencebetweenaheritable
mutationandasomaticmutation.
CentralDogmaOverview
CentralDogmaOverview
DNA
Transcription
mRNA
ribosome
mRNA
Translation
protein
Languages…
DNALanguagevs.ProteinLanguage
DNALanguage
3’ – GTGCA – 5’
5’ – CACGT – 3’
ThelanguageofDNAiswritteninnucleotides.
ProteinLanguage
Thelanguageofproteiniswritteninaminoacids
CentralDogma
DNA
Transcription
mRNA
ribosome
mRNA
Translation
protein
AnAcademicTranscript:
Acopyofyourgrades
ConnectingtheLanguages
TranscribingversusTranslating
- Transcribemeans:torewrite
- Translatingmeans:tochangelanguage
TranslationExample:
3partsgravel,2partssand,1partcement.
à
3 partes de grava, 2 partes de arena, 1 parte de cemento.
à
三石 二砂 一水泥
TheLanguageofGenetics
DNALanguagevs.ProteinLanguage
• DNAiswritteninthelanguageofnucleotides.
• AmessageonDNAcanbetranscribed (copied)
ontoapieceofmRNA.
• AmessageonmRNAcanbetranslated intoa
chainofaminoacids.
• Proteinsarewritteninthelanguageofamino
acids.
DNAà mRNAà AminoAcids
5’– CCACTGATAGACCTT –3’
3’– GGTGACTATCTGGAA –5’
non-TemplateStrand
TemplateStrand
ThepieceofmRNAthatismadefromathis
pieceofDNAisnearlyidenticaltothe
non-templatestrand.
mRNA:5’– CCACUGAUAGACCUU –3’
DNAà mRNAà AminoAcids
Template:
5’–CCACTGATAGACCTT–3’
3’–GGTGACTATCTGGAA–5’
mRNA:
5’–CCACUGAUAGACCUU–3’
Non-Templ:
non-Template
Strand
Template
Strand
HowdoweTRANSLATEthismRNAmoleculeintoaproteinmolecule?
TheTranslationKey:
© 2011 Pearson Education, Inc.
ImportantPropertiesoftheCode
• Itisredundant:Allaminoacidsexcepttwoare
encodedbymorethanonecodon.
• Itisunambiguous:Onecodonnevercodesformore
thanoneaminoacid.
• Itisnearlyuniversal:Withafewminorexceptions,all
codonsspecifythesameaminoacidsinallorganisms.
• Itisconservative:Thefirsttwobasesareusuallyidentical
whenmultiplecodonsspecifythesameaminoacid.
AllaminoacidsSTARTwithan H3N+ andENDwithaCOO-
AllaminoacidsSTARTwithan H3N+ andENDwithaCOO-
AllaminoacidsSTARTwithan H3N+ andENDwithaCOO-
GeneticLanguages
and
Mutations
GeneticLanguages
and
Mutations
TwoTypesofMutations
Asomaticmutationisnotpassedonto
offspring.
Aheritablemutationoccursduringmeiosisand
affectssexcells.Itresultsinnewalleles!
What isaMutation?
AnerrorintranscriptiondoesNOTresultina
changetotheDNA.
AnerrorintranslationdoesNOTresultina
changetotheDNA.
OnlyanerrorinDNAreplicationwillleadtoa
changeinDNA.
What isaMutation?
…and,onlyanerrorinmeioticDNA
AnerrorintranscriptiondoesNOTresultina
replicationwillresultinaheritablemutation.
changetotheDNA.
AnerrorintranslationdoesNOTresultina
changetotheDNA.
OnlyanerrorinDNAreplicationwillleadtoa
changeinDNA.
Cancer…
…istheresultofatypeofsomaticmutation
thatoccursduringmitosisandisnotpassedon
tooffspring.
(Notallsomaticmutationsleadtocancer.)
TypesofHeritableMutations…
PointMutations
• PointmutationsoccurwhentheDNA
polymeraseinsertsthewrongbaseintothe
newlysynthesizedstrandofDNA.
PointMutations
• Pointmutationsmaybeasaresultofa
substitution oraninsertion/deletionandmaybe:
– Silentmutations.
• Doesnotchangetheaminoacidsequenceofthegene
product.
– Missense mutations.
• Resultinchangesintheaminoacidsequenceofthe
encodedprotein.
– Nonsensemutations.
• Resultsinastopcodon.
Mutationsandtheirimpacts
Mutationsandtheirimpacts
Mutationsandtheirimpacts
Mutationsandtheirimpacts
Mutationsandtheirimpacts
DescribingaHeritableMutation:
ThreeCategories:
1. Whathappened?
– Insertion,deletion,substitution.
2. Whatwastheimpactontheprotein?
– Missense,nonsense,silent
3. Whatwasthereadingframe?
– Frameshift
YouShouldBeAbleTo…
1. AnalyzeapieceofDNAanddeterminethe
aminoacidsequencethatisultimately
produced.
2. Compareandcontrastthreedifferenttypes
ofmutation,andthethreepotential
implicationsofmutation.
3. Describethedifferencebetweenaheritable
mutationandasomaticmutation.
GeneticLanguages
and
Mutations