Genetics

Question 1

trinucleotide expansion: friedrich ataxia

Answer 1

GAA

ataxic GAAit

Question 2

Angelman

Answer 2

MAMA

• maternal deleted (dad silenced)
• laughter
• ataxia

Question 3

repair damaged strand by using a complementary strand from intact homologus

Answer 3

homologus recombination

Question 4

anticipation

Answer 4

increased severity or earlier onset of disease in later generations

Question 5

trinucletodie expansion: fragile x

Answer 5

CGG

chin
giant
gonads

Question 6

pleiotrophy

Answer 6

1 gene contributes to MANY phoenotypes

e.g. PKU, homocysterinuria

Question 7

splice site mutation

Answer 7

alters intron removal from pre-mrna

Question 8

nonsense mutation

Answer 8

codes for premature stop codon

Question 9

loss of heterozygosity

Answer 9

2 hit hypothesis of tumour spressors

Question 10

dominant negative mutation

Answer 10

nonfuncitonal altered protein also prevents normal gene product from funcitonin

Question 11

base excision repair (non bulky)

Answer 11

GEL PLease

• glycosylase
• endonucleause (5’ end)
• lyase (3’ end)
• DNA polymerase B
• ligase

spontaineous, toxic deamination

Question 12

variable expressivity

Answer 12

patients with same genotype with DIFFERENT phenotypes

e.g. NF1

Question 13

uniparental disomy

Answer 13

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

Question 14

nonhomologous end joining

Answer 14

ataxia telangiectasia

• blanching nests of distended capillaries
• recurrent sinupulmonary infections

Question 15

ataxia telangiectasia

Answer 15

nonhomologous end joining

Question 16

gonadal mosaicism

Answer 16

mutation only in egg or sperm

-suspect if parents and relatives do not have disease

Question 17

nonstop mutation

Answer 17

base subsitution within stop codon results in continued translation

Question 18

trasversion mutation

Answer 18

purine to pyrimidine

pyrimidine to purine

Question 19

Lynch

Answer 19

mismatch repair

Question 20

homologous recombination

Answer 20

BRCA

Fanconi anemia

Question 21

trinucleotide expansion: myotonic dystrophy

Answer 21

CTG

cataracts
toupee (bald)
gonadal atrophy

Question 22

conservative mutation

Answer 22

base codes for different a.a. with similar structure

Question 23

mosaicism

Answer 23

present of genetically distinct cell lines in same individual

Question 24

allelic heterogeneity

Answer 24

DIFFERENT mutations in SAME locus produce SAME phenotype

b-thalassemia

Question 25

somatic mosaicism

Answer 25

mutation arises from mitotic errors AFTER fertilization, propgates through multiple tissues or organs

Question 26

BRCA | Fanconi anemia

Answer 26

homologus recombination

Question 27

spontaneous toxic deamination

Answer 27

base excision repair

Question 28

locus heterogeneity

Answer 28

mutations at DIFFERENT loci can produce SIMILAR phenotype | albinism, marfanoid, familial hypercholesterolemia

Question 29

mismatch repair (wrong base)

Answer 29

Lynch syndrome

Question 30

transition mutation

Answer 30

purine to purine | pyrimidine to pyrimidne

Question 31

Prader Willi

Answer 31

POP - paternal deleted (mom silenced) - over eating - hypotonia - intellectual disability

Question 32

nucleotide excision repair (bulky)

Answer 32

xeroderma pigmentosum

Question 33

frameshift mutation

Answer 33

deleting or adding a number of bases that is NOT divisible by 3

Question 34

base-specific glycosylase removes the bad base | non-bulky

Answer 34

base excision repair

Question 35

a new strand is made, then mismatched nucleotides are removed

Answer 35

mismatch repair

Question 36

heteroplasmy

Answer 36

presence of both normal + mutated mtDNA --> get variable expression in mito-inherited diseases

Question 37

endonuclease release oligonucleotides with damaged bases | bulky

Answer 37

nucleotide excision repair

Question 38

join 2 ends of DNA fragments to repair DS breaks

Answer 38

nonhomologous end joining

Question 39

incomplete penetrance

Answer 39

risk of expressing phenotype = % penetrance x prob of inheriting genotype

Question 40

xeroderma pigmentosum

Answer 40

nucleotide excision repair

Question 41

linkage disequilibrium

Answer 41

tendency for certain alleles at 2 linked loci to occur toether more or less often than expected by chance

Question 42

trinucleotide expansion: Huntington

Answer 42

CAG | caudate, Ach, Gaba