Genetics Flashcards

1
Q

Incomplete penetrance example

A

BRCA gene mutations do not always result in breast or ovarian cancer

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2
Q

Loss of heterozygosity

A
Tumor suppressor genes require one mutation and deletion/mutation of second gene before cancer develops
NOT TRUE OF ONCOGENES 
Rb and two hit hypothesis 
Lynch syndrome 
Li-Fraumeni syndrome
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3
Q

Linkage disequilibrium

A

Tendency for alleles at 2 linked loci to occur together more or less often than expected by chance. Measured in a population and varies with different populations.

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4
Q

Mosaicism

A

Genetically distinct cell lines in the same individual
McCune-Albright syndrome: mutation in G protein signaling
–unilateral cafe-au-lair spots, precocious puberty, multiple endocrine abnormalities,

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5
Q

McCune-Albright Syndrome

A

Mosaicism -only survivable in patients with Mosaicism
Mutation affecting G protein signaling
Unilateral cafe au lait spots
Polyostotic fibrous dysplasia, precocious puberty, multiple endocrine abnormalities
LETHAL if mutation is prior to fertilization

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6
Q

Locus heterogeneity

A

Mutations at different loci can produce a similar phenotype

Ex: albinism

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7
Q

Allelic heterogeneity

A

Different mutations in the same locus produce the same phenotype
Ex: beta thalassemia

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8
Q

Heteroplasmy

A

Presence of both normal and mutated mtDNA

Variable expression in mitochondrially inherited disease

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9
Q

Uniparental disomy

A

Consider in an individual manifesting with a recessive disorder when only one parent is a carrier

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10
Q

Hardy Weinberg population

A
  1. No mutation occurring at the locus
  2. Natural selection not occurring
  3. Completely random mating
  4. No net migration
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11
Q

Imprinting

A

Only one allele is active and the other one is inactive

Ex: angelman and prader-willi

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12
Q

Prader-Willi syndrome

A

Paternal is mutated
Maternal imprinting–mother’s gene is usually silent (child may also receive two “silent” genes from the mother)
Child has hyperphagia, obesity, intellectual disability, hypogonadism and hypotonia
Will used to eat his feelings and was not aroused.

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13
Q

Angelman syndrome

A

Maternal deleted/mutated
Paternal imprinting
“Happy puppet” – It’s all in their head (seeing Angels)
Seizures, ataxia, severe MR

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14
Q

Pleiotropy

A

One gene contributes to multiple phenotypic effects

PKU-musty odor, light skin and intellectual disability

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15
Q

Hypophosphatemic Rickets

A

X linked dominant
Vit D resistant Rickets
Increased phosphate wasting at proximal tubule

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16
Q

Mitochondrial Inheritance

A

Mitochondrial myopathies
Lactic acidosis, CNS disease, myopathy
Ex: MELAS–failure in oxidative phosphorylation
“ragged red fibers” on muscle biopsy