Genetics Flashcards
trinucleotide expansion: friedrich ataxia
GAA
ataxic GAAit
Angelman
MAMA
- maternal deleted (dad silenced)
- laughter
- ataxia
repair damaged strand by using a complementary strand from intact homologus
homologus recombination
anticipation
increased severity or earlier onset of disease in later generations
trinucletodie expansion: fragile x
CGG
chin
giant
gonads
pleiotrophy
1 gene contributes to MANY phoenotypes
e.g. PKU, homocysterinuria
splice site mutation
alters intron removal from pre-mrna
nonsense mutation
codes for premature stop codon
loss of heterozygosity
2 hit hypothesis of tumour spressors
dominant negative mutation
nonfuncitonal altered protein also prevents normal gene product from funcitonin
base excision repair (non bulky)
GEL PLease
- glycosylase
- endonucleause (5’ end)
- lyase (3’ end)
- DNA polymerase B
- ligase
spontaineous, toxic deamination
variable expressivity
patients with same genotype with DIFFERENT phenotypes
e.g. NF1
uniparental disomy
offspring gets 2 copies of chromomse from 1 parents (and none from the other –> can cause problems due to imprinting)
heterodIsomy (heterozygous): meiosis I error
IsodIsomy (homozygous): meiosis II error
nonhomologous end joining
ataxia telangiectasia
- blanching nests of distended capillaries
- recurrent sinupulmonary infections
ataxia telangiectasia
nonhomologous end joining
gonadal mosaicism
mutation only in egg or sperm
-suspect if parents and relatives do not have disease
nonstop mutation
base subsitution within stop codon results in continued translation
trasversion mutation
purine to pyrimidine
pyrimidine to purine
Lynch
mismatch repair
homologous recombination
BRCA
Fanconi anemia
trinucleotide expansion: myotonic dystrophy
CTG
cataracts
toupee (bald)
gonadal atrophy
conservative mutation
base codes for different a.a. with similar structure
mosaicism
present of genetically distinct cell lines in same individual
allelic heterogeneity
DIFFERENT mutations in SAME locus produce SAME phenotype
b-thalassemia
somatic mosaicism
mutation arises from mitotic errors AFTER fertilization, propgates through multiple tissues or organs
BRCA
Fanconi anemia
homologus recombination
spontaneous toxic deamination
base excision repair
locus heterogeneity
mutations at DIFFERENT loci can produce SIMILAR phenotype
albinism, marfanoid, familial hypercholesterolemia
mismatch repair (wrong base)
Lynch syndrome
transition mutation
purine to purine
pyrimidine to pyrimidne
Prader Willi
POP
- paternal deleted (mom silenced)
- over eating
- hypotonia
- intellectual disability
nucleotide excision repair (bulky)
xeroderma pigmentosum
frameshift mutation
deleting or adding a number of bases that is NOT divisible by 3
base-specific glycosylase removes the bad base
non-bulky
base excision repair
a new strand is made, then mismatched nucleotides are removed
mismatch repair
heteroplasmy
presence of both normal + mutated mtDNA –> get variable expression in mito-inherited diseases
endonuclease release oligonucleotides with damaged bases
bulky
nucleotide excision repair
join 2 ends of DNA fragments to repair DS breaks
nonhomologous end joining
incomplete penetrance
risk of expressing phenotype = % penetrance x prob of inheriting genotype
xeroderma pigmentosum
nucleotide excision repair
linkage disequilibrium
tendency for certain alleles at 2 linked loci to occur toether more or less often than expected by chance
trinucleotide expansion: Huntington
CAG
caudate, Ach, Gaba
