GENETICS - Inheritance types Flashcards

1
Q

What are the X-linked dominant conditions? (3)

A
  1. Aicardi syndrome
  2. Incontinentia pigmentii
  3. Alport’s syndrome
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2
Q

Which chromosome defect is associated with retinoblastoma?

A

Rb gene located on long arm chromosome 13

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3
Q

What diseases are examples of mitrochondrial inheritance? (6)

A
  1. Lebers hereditary optic atrophy
  2. Mitochondrial encephalopathy, lactic acidosis and stroke (MELAS)
  3. Myoclonus epilepsy associated with ragged-red fibres (MERRF)
  4. Kearns-Sayre syndrome (KSS)
  5. Pearson syndrome
  6. Diabetes/Deafness
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4
Q

Consanguinity is more likely to have which type of inheritance?

A

Recessive

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5
Q

What is X-linked inheritance?

A

mode of inheritance in which a mutation in a gene on the X chromosome causes the phenotype to be always expressed in males
and in females who are homozygous for the gene mutation

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6
Q

What are the patterns of inheritance in X-linked? (3)

A
  1. Father cannot pass X-linked disease to son as father always passes Y chromosome –> means mother of X-linked male always is responsible.
  2. More commonly expressed in males than females.
  3. Skips generations - affected grandfather will not have an affected son, but could have an affected grandson through his daughter
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7
Q

How can some female heterozygotes be affected in X-linked inheritance?

A

Lyonisation - inactivation of one of the two X chromosomes in every somatic cell.

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8
Q

What is the inactived X chromosome known as in lyonisation?

A

The Barr Body

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9
Q

What are the most common X-linked ocular diseases (8)

A
  1. Red-Green colour blindness
  2. Duchennes muscular dystrophy
  3. Fabry Disease
  4. Lowe Syndrome
  5. Ocular albinism
  6. Retinitis pigmentosa
  7. Choroideraemia
  8. Retinoschisis
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10
Q

What does mitochondrial DNA encode for?

A

Encodes for tRNA and ribosome RNA for mitochondrial protein synthesis

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11
Q

Why does mitochondrial DNA have a higher mutation rate than nuclear DNA? (5)

A
  1. DNA polymerases are more inaccurate
  2. mtDNA more suspectible to oxidative damage.
  3. Alkylating agents affect mtDNA more
  4. repair mechanisms underdeveloped
  5. No introns - likely impact a coding sequence if mutation arises.
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12
Q

What are the main inheritance patterns for mitochondrial inheritance? (3)

A
  1. Males cannot transmit
  2. Both males/females affected if mother has defective gene
  3. An affected mother passes defect to all children but only daughters will trasmit.
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13
Q

What is the mode of inheritance of chromatopsia?

A

X-linked recessive.

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14
Q
A
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