Non-Mendelian Inheritance Flashcards

(19 cards)

1
Q

MELAS

A
  • Mitochondrial Inheritance
  • Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like episodes
  • Hearing loss, diabetes, seizures, intellectual disability, cardiomyopathy
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2
Q

Heteroplasmy

A

Mixture of normal and abnormal mitochondrial DNA

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3
Q

Homoplasmy

A

All mitochondrial DNA is the same

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4
Q

Threshold Effect

A

A certain percentage of abnormal mitochondrial DNA is tolerated without symptoms

  • Clinical phenotype may vary depending on the percentage of abnormal mtDNA
  • Threshold varies depending on individuals and tissue types
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5
Q

Trinucleotide Repeat Disorders

A
  • Present throughout the genome
  • Stable during mitosis and meiosis
  • Sequence copy number is transmitted as polymorphism from parent to child
  • Increase in severity or earlier onset of a phenotype over successive generations
  • Formation of hairpin loop is a possible explanation for the expanded DNA replication product
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6
Q

Myotonic Dystrophy

A

-CTG Repeat
-Affects skeletal and smooth muscle as well as eye, heart endocrine system, and CNS
-Myotonia: sustained muscle contraction (extended firm hand shake)
-3 phenotypes:
Mild (Cataract and mild myotonia; Normal lifespan)
Classic (Muscle weakness and wasting, cataract, myotonia; possible shortened life span)
Congenital (Severe congenital hypotonia)

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7
Q

Fragile X Syndrome

A
  • CGG Repeat in FMR1 gene on X chromosome
  • Most common inherited cause of intellectual disability
  • Long face, large ears
  • Full mutation occurs upon complete methylation of FMR1 gene
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8
Q

Mosaicism

A

Presence of more than one cell line in an individual; could be somatic or gonadal

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9
Q

Somatic Mosaicism

A
  • Usually caused by post-zygotic mutation

- Variable degree of disease severity

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10
Q

Mosaic Down Syndrome

A
  • May be less severely affected than with full trisomy 21

- Phenotype/severity depends on proportion of cells with trisomy 21 in each tissue type

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11
Q

Pallister-Killian Syndrome

A
  • Mosaic Tetrasomy 12p
  • Low muscle tone, characteristic facies, high arched palate, hypopigmentation, extra nipples, developmental delays, and diaphragmatic hernias
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12
Q

Gonadal Mosaicism

A
  • Individual unaffected w/ syndrome

- Mutation occurred in precursor sperm or egg

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13
Q

Imprinting

A

Different epigenetic modification of the maternal paternal genetic contributions to the zygote

  • Some genes are expressed preferentially from the maternal or paternal alleles
  • Differences in phenotype when; uniparental disomy, heterozygous deletion or mutation for an imprinted region of a chromosome or gene
  • ie. Triploidy
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14
Q

Cystic Fibrosis

A
  • Uniparental Disomy (UPD)
  • Explanations:
    • Non-paternity
    • De novo mutation
    • Large deletion on paternal chromosome
    • Maternal uniparental disomy
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15
Q

Russel-Silver Syndrome

A

-Growth disorder with prenatal onset
-small triangular face with distinctive facial features
~10% cases due to maternal UPD of chromosome 7

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16
Q

Prader-Willi Syndrome

A
  • UPD of chromosome 15 from the MOTHER
  • Hypotonia, Intellectual Disability, Hyperphagia (pathological overeating)
  • Lack of expression from chromosome 15 genes that are normally only expressed from the Paternal allele
17
Q

Angelman Syndrome

A
  • UPD of chromosome 15 from the FATHER
  • Severe intellectual disability, movement disorder, and seizures
  • Lack of expression from chromosome 15 genes that are normally only expressed from the MATERNAL allele
18
Q

Heterodisomy

A
  • Non-disjunction occurs in Meiosis I

- Gametes have a pair of homologous chromosomes

19
Q

Isodisomy

A
  • Non-disjunction occurs in Meiosis II

- The non-disjunction will produce a gamete with two identical copies of a homolog chromosome