The Genetic Basis of Complex Inheritance Flashcards

1
Q

What are the 3 laws that fall under medelian inheritance?

A
  • The law of dominance
  • The law of segregation
  • The law of independent assortment
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2
Q

What is included in non-mendelian inheritance?

A
  • gene conversion

- intermediate phenotype

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3
Q

What inheritance patterns are seen in non-mendelian inheritance and what mechanism brings them about?

A
  • Incomplete penetrance: environemental factors and genetic modifiers
  • Genomic imprinting: variants from parents
  • Extranuclear Inheritance: mitochondria mutations
  • Anticipation: triple repeat expansion
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4
Q

What is penetrance?

A

the frequency with which a trait is manifested by individuals carrying the gene

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5
Q

What is the risk calculation?

A

Penetrance of mutant over penetrance of wild type

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6
Q

How can the CF phenotype vary?

A

In severity and organs affected

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7
Q

What are genetic modifiers?

A

Genes that have small quantitative effects on the level of expression of another gene

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8
Q

What are environmental factors?

A
  • lifestyle
  • diet
  • smoke
  • alcohol
  • drugs
  • stress
  • air pollution
  • chemicals
  • infection
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9
Q

How can genetic diseases be described?

A
  • rare
  • genetics simple
  • uni-factorial
  • high recurrence rate
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10
Q

How can environmental diseases be described?

A
  • common
  • genetics complex
  • multi-factorial
  • low recurrence rate
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11
Q

What is genomic imprinting?

A

Genes expressed from only one chromosome and is parent of origin dependent

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12
Q

What are epigenetic modifications?

A

Heritable changes in gene function that cannot be explained by changes in DNA sequences

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13
Q

What genetic mechanisms can be involved in inheritance?

A
  • deletions
  • point mutations
  • imprinting errors
  • uniparental disomy
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14
Q

What are the 2 different types of uniparental diploidy?

A
  • gynogenic

- androgenic

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15
Q

Describe gynogenic uniparental diploidy.

A
  • 2 maternal genomes
  • mass of embryo
  • ovarian teratoma
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16
Q

Describe androgenic uniparental diploidy.

A
  • 2 paternal genomes
  • mass of placenta
  • hydatidiform mole
17
Q

What are 2 examples of imprinting disorders?

A
  • Angelman syndrome

- Prader Willi syndrome

18
Q

Describe Angelman syndrome.

A
  • epilepsy
  • severe mental retardation
  • awkward gait
  • inappropriate laughter
19
Q

Describe Prader-Willi syndrome.

A
  • hyptonia
  • mild-moderate mental retardation
  • short stature
  • marked obesity
20
Q

What chromosomal region do AS and PWS occur in?

A

15q11-13

21
Q

What are the characteristics of a mutation hotspot?

A
  • lack of efficient DNA repair system
  • lack of protective proteins such as histones
  • damaged by reactive oxygen species such as free radicals
22
Q

What is polyploidy?

A

Up to thousands of mitochondria per cell,

23
Q

What is homoplasmy

A

A cell that has uniform collection of mtDNA and presents no disease

24
Q

What is heteroplasmy?

A

When a cell has some mitochondria that have a mutation in the mtDNA and some that do not. If there is ahigh percentage of mutation disease can occur.

25
Q

What does mitochondrial disease do?

A

affects tissue with high metabolic demand

26
Q

What are the 3 major myopathies of mitochondrial disease?

A
  • Myoclonic epilepsy with ragged red fibres(MERRF)
  • Mitochondrial myopathy, encephalopathy, lactic acidosis, stroke-like symptoms (MELAS)
  • Chronic progressive external opthalmoplegia (CPEO)
27
Q

What other mitochondrial disease are there?

A
  • Leber’s hereditary optic neuropathy (LHON) causes loss of central vision
  • Leigh’s syndrome causes encephalopathy
  • Diabetes meliituse and deafness (DAD)
28
Q

What is anticipation?

A

The disease presents at earlier age and/ or increasing severity in succeeding generations

29
Q

What are 3 examples of diseases which exhibit anticipation?

A
  • Huntington’s
  • Myotonic dystrophy
  • Fragile X syndrome