Mutations And Repair

Front 1

Mutation types

Back 1

-Point:change in 1 bp
-Deletions/Duplications: bases are added or removed from the normal sequence
-Translocations:transfer of genes from 1 chromo location to another

Front 2

Types of point mutations

Back 2

-transitions:purine to purine,or pyrim to pyrim
-transversions:purine to pyrimadine (A,G->C,U,T)or vice versa

Front 3

Results of point mutations

Back 3

silent-trasnition,asymptomatic,codesfor same protein
nonsense-transversion,creates a stop codon,premature termination of translation, complete loss of protein function
missense-transition,changes code to a diff protein
frameshift-insertions & del of anyting other than 3bp's =shift in reading frame,premature stop codon & loss of protein function

Front 4

Spontaneous point mutations

Back 4

hydrolysis rxns:
-hydrolysis of glycosidic bond b/t purine and deoxyribose=no base just OH on C#1
-hydrolysis of amino grp on cytosine=uracil
tautomeric shifts:shifts durng replication
-imino form of A pairs w/C
-enol form of T pairs w/G
-rare

Front 5

Deamination of methyl cytosine & deaminating agents

Back 5

Both = errors in replication
-C is methylated = T
-asymptomatic
-common
Agents:
nitrous acid turns A to hypoxanthene & C to uracil

Front 6

Pyrimadine dimers

Back 6

-UV radiation i.e. sunlight, causes 2 T dimers to occur in the same strand of a dbl helix

Front 7

Intercalating agents

Back 7

-agents insert themselves b/t bases
-mutations occur as frameshifts
i.e. ethidium bromide,aflotoxin-
causes G to T =transverion=liver CA

Front 8

Postreplication mismatch repair

Back 8

-removes mismatches,ins & del from replication errors
-enzymes can tell old strand from new b/c old strand is methylated

Front 9

2 main repair principles

Back 9

-base excision=single base repair
-nucleotide excision=bulky modification

Front 10

Repair mechanisms

Back 10

-3'exonuclease activity=replication errors
-post replication mismatch=replication errors
-direct repair=methylated bases, pyrim dimers in bact.
-base excision=breaks bond b/t sugar & nonstandard base
-AP endonuclease= takes out empty sugar
-nucleotide excision=bulky lesions

Front 11

TT dimer repair

Back 11

-scan for distortion i.e. abn width of helix
-excise region
-fill in
-ligate

Front 12

Problems w/ repair rxns

Back 12

-99% succsessful
-repair DNA pols are sloppy than in replication
-no post replication repair after a repair DNA pol

Front 13

Cocayne syndrome

Back 13

-defect of nucleotide excision repair for transcribed genes
-poor growth
-neuro probs
-early senility
-AR
-2 types

Front 14

Xeroderma pigmentosum

Back 14

-defect of genome wide nucleotide excision repair
-hyper sensitive to sun
-neuro probs
-30 yr.dec in life expectancy
-inc risk of skin CA
-AR
-7 types

Front 15

Complementation

Back 15

XP is present if both copies of an XP gene is mutated=
1 cell provides a protein that the other cell needs & vice versa
-if no complementation then both cells are mutated in the same gene

Front 16

Hereditary non-polyposis colon CA

Back 16

-defect in post replication mismatch repair
-80% risk of dev colon CA
-dominant inheritance