Mutation.pdf pdf Indian students knowledgeable

Document

1. Mutations
MD MAHIDUL ISLAM
MSc, PGD

2. Whatisagenemutation?
Mutationsarechangesin geneticmaterial–changesin
DNAcode–thusachangeina gene(s)
Ingenemutations,theDNAcode willhaveabase(ormore)
missing,added,orexchangedin acodon.
2

3. Howcommonaremutations?
Mutationsoccursata frequencyofabout1inevery 1billionbase
pairs
Everybodyhasabout6 mutationsineachcellintheir body!

4. Classificationofmutation
A.Basedonthesurvivalofanindividual:
1.Lethalmutation–whenmutationcausesdeathofallindividuals
undergoingmutationareknownaslethal
2.Sublethalmutation-causesdeathof90%individuals
3.Vitalmutation-whenmutationdon’taffectthesurvivalofan individual are
knownasvital
4.Supervitalmutation–Thiskindofmutationenhancesthe
survivalofindividual

5. 5
B.Basedoncausesofmutation:
1.Spontaneousmutation-
Spontaneousmutationoccursnaturallywithoutanycause.Therateofspontaneous mutationisvery
sloweg-Methylationfollowedbydeaminationofcytosine.
Rateofspontaneousmutationishigherineukaryotesthanprokaryotes.
Eg.UVlightofsunlightcausingmutationinbacteria.
2.InducedMutation-
Mutationsproducedduetotreatmentwitheitherachemicalorphysicalagentare calledinduced
mutation.
Theagentscapableofinducingsuchmutationsareknownasmutagen.useof inducedmutationfor
cropimprovementprogramisknownasmutationbreeding.
Eg.X-rayscausingmutationincereals

6. C.Basedontissueoforigin
1.Somaticmutation-
A mutationoccurringinsomatic celliscalledsomatic mutation.
Inasexuallyreproducingspeciessomaticmutationstransmitsfrom one
progeny to thenextprogeny
2.GerminalMutation-
Whenmutationoccuringameticcellsor reproductivecellsare knownas
germinalmutation.
Insexuallyreproductivespeciesonlygerminalmutationare
transmittedtothenextgeneration

7. Mutationsareamajorsourceofgenetic
variationina populationincreasing
biodiversity.
Somevariationsmayhelpthemto
survivebetter.
Howdomutations affectapopulation?

8. TypesofMutations

9. TypesofChromosome Mutations
•MayInvolve:
–Changingthe structureofa
chromosome
–Thelossor gainofpart of a
chromosome

10. ChromosomeMutations
•Fivetypesexist:
–Deletion
–Inversion
–Translocation
–Nondisjunction
–Duplication

11. Deletion
•Duetobreakage
•Apieceof a chromosomeis
lost

12. Inversion
•Chromosomesegment
breaks off
•Segmentflipsaround
backwards
•Segmentreattaches

13. Duplication
•Occurswhena genesequenceis
repeated

14. Translocation
•Involvestwo chromosomesthat are
NOThomologous
•Partofone chromosomeis
transferredto another
chromosome

15. Nondisjunction
•Failureofchromosomesto separateduringmeiosis
•Causesgametetohavetoomany ortoofewchromosomes
•Disorders:
–DownSyndrome–three21
st
chromosomes
–TurnerSyndrome–singleXchromosome
–Klinefelter’sSyndrome–XXYchromosome

17. ChromosomeMutation
Animation

18. TypesofGeneMutations
Pointmutationoccurswhenthe basesequenceofacodonis
changed.(ex.GCAischangedto GAA)
Thereare3 types:
•Substitution
•Deletion
•Insertion
Alsocalled
frameshift
mutations

19. SubstitutionMutations
MutatedDNA:CGA–TGC–TTC
NormalDNA:CGA–TGC–ATC
Alanine–Threonine-stop
Alanine–Threonine-Lysine
What has happened to the DNA?

20. SubstitutionMutations
Alanine–Threonine-Lysine
MutatedDNA:CGA–TGC–TTC
Thisisasubstitutionmutation.
Asinglenitrogenbaseis substitutedfor
anotherinacodon.
Itmayormaynotaffecttheamino acidor
protein.
NormalDNA:CGA–TGC–ATC
Alanine–Threonine-stop
20

21. SubstitutionMutations
Basesubstitutionscanbedividedintotwo
subtype:
Transitionmutation
Atransversionistheoppositethereplacementofabaseofone
chemicalcategorybyabaseoftheother
Purine Purine
A>G,G>A
Pyrimidine Pyrimidine
T>C,C>T
Transversionmutation
Atransversionistheoppositethereplacementofabaseofone
chemicalcategorybyabaseoftheother.
Purine Pyrimidine
A>C,A>T,G>C ,G>T
Pyrimidine Purine
T>A,T>G,C>T,C21>G

22. InsertionMutations
NormalDNA:CGA–TGC–ATC
Alanine–Threonine–stop
MutatedDNA:CGA–TAG–CAT–C
Alanine–Isoleucine–Valine

23. InsertionMutations
MutatedDNA:CGA–TAG–CAT–C
Alanine23–Leucine-Valine
Thisisaninsertionmutation.
Anitrogenbaseisinserted/addedto
thesequence.
Itcausesthetriplet“framestoshift”.
Italwaysaffectstheaminoacidsand
consequentlytheprotein.
NormalDNA:CGA–TGC–ATC
Alanine–Threonine-stop

24. NormalDNA:CGA–TGC–ATC
Alanine–Threonine–stop
MutatedDNA:CGA–TCA-TC
Alanine–Serine
DeletionMutations

25. DeletionMutations
Thisisadeletionmutation.
Anitrogenbaseisdeleted/removed fromthesequence.
Itcausesthetriplet“framestoshift
Italwaysaffectstheaminoacidsand consequentlytheprotein.
NormalDNA:CGA–TGC–ATC
Alanine–Threonine–stop
MutatedDNA:CGA–TCA-TC
Alan2in5e–Serine

26. FrameshiftMutation
Insertingordeleting oneormore nucleotides
Changesthe“readingframe”like changingasentence
Proteinsbuiltincorrectly

27. CLASSIFICATIONOFPOINTMUTATIONS
DEPENDINGONEFFECTS
MUTATION:
•Missensemutation
•Silentmutation
•Non-sensemutation

28. MISSENSEMUTATION:
•Thenewcodoncausesan incorrectAMINOACIDtobe insertedinto
theprotein.
•Thiseffectonthefunctionofthe proteindepend onwhatis insertedin
placeofnormalamino acid.
28

30. NON-SENSEMUTATION:
Whenabasesubstitutionresultsina stopcodon
ultimatelytruncating translationandmostlikely
leadingtoanonfunctional protein.

32. SILENTMUTATION:
Silentmutationdoesnotcauses anychangeinaminoacid.
(Silentmutationcodesforsame amino acid)
DNA:
mRNA:
>TTC
AAG
TTT
AAA-
Lysine-Lysine

33. 33