Patterns of Inheritance Flashcards

1
Q

What is Pleiotrophy?

A

A mutation that can produce multiple distinct phenotypes that may or may not appear in a particular individual

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2
Q

What is a kindred?

A

A group of human beings each of which is related, genetically or by marriage to ever other member of the group

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3
Q

What is the proband?

A

Family member who draws attention to a pedirgree

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4
Q

What is an index case?

A

the clinically affected family member through whom attention is first drawn to a pedigree of particular interest to human genetics

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5
Q

What is penetrance?

A

The probability that a gene will have any phenotypic expression at all

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6
Q

What is expressivity?

A

The severity of expression of the phenotype

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7
Q

What are the characteristics of Autosomal dominant inheritance?

A
  • Multiple generations affected
  • Males and females are affected in equal proportion
  • Male to male is possible
  • Each offspring of an affected parent has a 50% of being affected
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8
Q

Describe Polycystic Kidney disease.

A
  • Autosomal dominant
  • Renal cysts, progressive renal failure, extrarenal problems
  • Late onset
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9
Q

What are the characteristics of Autosomal recessive inheritance?

A
  • Males and females are equally likely to be affected
  • Both parents must be carriers to have an affected child
  • Recurrence risk is 25% for each offspring of carrier parents
  • Certain diseases are more common to certain ehtnicities
  • Inquire about consanguinity
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10
Q

Describe Tay-Sachs disease.

A

Autosomal recessive

Severe mental and physical deterioration and death by 2 or 3

Higher incidence in Ashkenazi Jews

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11
Q

Describe Phenylketonuria (PKU)

A

Autosomal recessive

Mental retardation, fair skin, eczema, epilepsy

Preventable if prompt dietary treatment

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12
Q

What is Consanguinity?

A

A genetic relationship where individuals have at least one common ancestor in the preceding few generations

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13
Q

What is an isonymous marriage?

A

Marriage between persons with the same surname

Not necessarily indicative of consanguinity

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14
Q

What are the characteristics of X-linked recessive inheritance?

A
  • Incidence much higher in males
  • All daughters of affected males will be carriers
  • Sons of females have a 50/50 chance
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15
Q

Lyonization may make symptoms milder in X-linked recessive disorders. What are some exceptions to this?

A
  • Turner Syndrome (XO)
  • Extreme lyonization
  • Patients carrying X:autosome translocations
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16
Q

Describe Hemophilia A.

A
  • X-linked recessive

- Coagulation disorder leading to hemorrhaging

17
Q

Describe Duchenne muscular dystrophy

A
  • X-linked recessive

- Progressive muscle weakness, pseudohypertrophy of calf muscles

18
Q

What are the characteristics of X-linked dominant inheritance?

A

Twice as many affected females as males in large population

Affected heterozygous females should transmit to half of offspring

All daughters of affected males will be affected

19
Q

Describe Rett syndrome

A

Rare mental retardation syndrome in females, lethal in males

Ataxia, dementa, seizures

X-linked dominant

20
Q

Describe Hypophosphatemic rickets (Vit D resistant rickets).

A

X-linked dominant

Ability of kidney to reabsorb phosphate is reduced leading to hypophosphatemia

21
Q

What are the characteristics of mitochondrial inheritance?

A

Maternal origin

All offspring of an affected or carrier female are at risk of becoming affected themselves

All daughters of an affected or carrier female are at risk of transmitting the disease

22
Q

Describe Lever’s hereditary optic neuropathy (LHON)

A

Rapid, bilateral loss of central vision do to optic nerve death

Affects males and females

Mitochondrial inheritance

23
Q

Describe Kearns-Sayre Syndrome

A

External ophthalmoplegia

Pigmentary degeneration of the retina and cardiomyopathy

Mitochondrial inheritance

24
Q

What are the characteristics of Y-linked (holandric) inheritance?

A

Only males are affected

Only father to son transmission

25
Q

What are is pseudoautosomal inheritance?

A

Pertains to set of genes carried by both the X and Y chromosome, involved with a disorder known as sex reversal

26
Q

What are the clues to a translocation in a pedigree?

A

Recurrent miscarriages

Unexplained infertility

Mental handicap associated with unusual or dysmorphic appearance in more tha one individual related through phenotypically normal parents

Child or stillbirth with multiple malformation

27
Q

What are the 5 drivers for variation from Hardy-Weinberg equilibrium?

A

Mutation

Gene flow

Selective mating

Genetic drift

Selection