L3: Modes of Inheritance Flashcards

1
Q

Modes of Inheritance

A
  • Mendelian inheritance (single gene traits)
  • Multi-factorial inheritance
  • Non-traditional inheritance
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2
Q

Def of Mendelian Inheritance (Single Gene Traits)

A
  • The inheritance of single-gene disorders
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3
Q

Def of Locus

A

Specific position of gene on the chromosome

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4
Q

Def of Alleles

A
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5
Q

Introduction to Genetic Pedigree

A
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6
Q

Types of Mendelian Inheritance

A
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7
Q

Def of AD Inheritance

A
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8
Q

Risk of Transmission in AD Inheritance

A
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9
Q

Rules of AD Inheritance

A

โ€ฆ

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10
Q

Sex affected in AD Inheritance

A

Male & Female are affected in equal proportion

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11
Q

Generations affected in AD Inheritance

A
  • Transmitted from one generation to the next
  • Sporadic cases with high paternal age suggest new mutation
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12
Q

Transmission between sexes in AD Inheritance

A
  • All forms of transmission between sexes are observed (male to male - male to female // female to female - female to male)
  • Male to male transmission exclude the gene on X chrom
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13
Q

Examples of AD Inheritance

A
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14
Q

Sporadic cases with AD disorders suggest โ€ฆโ€ฆ..

A

New Mutation

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15
Q

Male to Male transmission exclude โ€ฆโ€ฆ..

A

X-Linked Inheritance

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16
Q

Def of AR Inheritance

A
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17
Q

Risk of Transmission in AR Inheritance

A
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18
Q

Sex affected in AR Inheritance

A

Male & Female are affected in equal proportion

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19
Q

Generations affected in AR Inheritance

A

Affected individual usually only in a single generation

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20
Q

Consanguinity supports โ€ฆโ€ฆ.

A

AR Inheritance

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21
Q

Examples of AR Inheritance

A
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22
Q

Factors affecting AD Gene Expression

A
  • Pleiotropy
  • variable Expressivity
  • Reduced penetrance
  • New Mutations
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23
Q

Def of Pleiotropy

A

A single gene (AD) that may give rise to two or more apparently unrelated effects.

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24
Q

Etiology of Pleiotropy

A
  • Different mutations in the same gene
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25
Q

Examples of Pleiotropy

A

In tuberous sclerosis, some affected individuals may have all features (learning difficulties, epilepsy, facial rashes,โ€ฆ)

26
Q

Def of Variable Expressivity

A
  • Striking variation in the clinical features of AD disorders from person to person, even in the same family.
27
Q

Examples of Variable Expressivity

A

PCKD

28
Q

Def of Reduced penetrance

A

Penetrance describes the frequency with which phenotypic manifestation of a gene are expressed.

29
Q

Examples of Reduced penetrance

A
30
Q

Def of New Mutations

A
  • AD disorders sometimes appear in a child of unaffected parents because of a spontaneous mutation
31
Q

Etiology of New Mutations

A
  • May be associated with advanced paternal age
32
Q

Examples of New Mutations

A
  • About 80% of patients with achondroplasia have experienced a mutation in (FGFR3) gene.
33
Q

Difference between penetrance & Expressivity

A
34
Q

Pseudodominance Inheritance

A
35
Q

Co-dominance Inheritance

A
36
Q

Incomplete Dominance

A
37
Q

Types of Sex Chromosome Inheritance

A
  • X Linked Inheritance
  • Y Linked Inheritance
38
Q

Types of X-Linked inheritance

A
  • XL Dominant
  • XL Recesive
  • Sex Controlled
  • Sex Limited
39
Q

X-Linked Dominant Inheritance

  • Whci sex is more affected?
A
  • Females are affected more frequently than males
  • Females are affected less severely than males
40
Q

X-Linked Dominant Inheritance

  • Transmission between sexes
A
  • Affected female can transmit the disorder to both male and female offspring
  • Affected males can only transmit the disorder to their daughters but not sons.
41
Q

In X-Linked Dominant Inheritance

  • Affected males can only transmit the disorder to โ€ฆ..
A

their daughters but not sons.

42
Q

Examples of X-Linked Dominant Inheritance

A
  • Hypophosphatemic rickets
  • Incontinentia pigmenti
43
Q

Def of X-Linked Recessive Inheritance

A
  • An x-linked recessive trait is one determined by a gene carried on the X chromosome and usually only manifest in males
44
Q

Risk of Transmission in X-Linked Recessive Inheritance

A
45
Q

Risk of Transmission in X-Linked Recessive Inheritance

  • Male affected married normal female (Hemophilia)
A
  • All daughters obligate carriers
  • All sons normal
46
Q

Risk of Transmission in X-Linked Recessive Inheritance

  • Carrier female (X-LR married normal male
A
  • Sons: 50% chance affected
  • Daughters: 50% chance carrier
47
Q

X-Linked Recessive Inheritance

  • Which sex is more affected?
A
  • Males usually only affected.
48
Q

A male with mutant allele on his single x chromosome is said to be โ€ฆ. for that allele.

A

hemizygous

49
Q

X-Linked Recessive Inheritance

  • Transmission Between Sexes
A
  • Transmitted through unaffected carrier females to their sons
  • Males cannot transmit the disorder to their sons i.e. no male to male transmission.
  • A male transmits his x chromosome to each of his daughters and his Y chromosome to each of his sons.
50
Q

X-Linked Recessive Inheritance

  • Examples
A
  • Hemophilia A
  • G6PD deficiency
  • Muscular dystrophy
  • Color blindness
51
Q

Explain Sex controlled inheritance

A
  • Some genes gives an effect in male different from that in female
52
Q

Examples of Sex controlled inheritance

A

Tone of voice (High pitch in male and vice versa)

53
Q

Explain Sex limited inheritance

A

Gene expresses itself in only one sex and not the other

54
Q

Example of Sex limited inheritance

PLUS Y-Linked Inheritance

A

Gene determining a heavy beard in male

55
Q

Def of Multi-Factorial Inheritance

A
56
Q

In Multi-Factorial Inheritance

  • The magnitude of the trait is determined by:
A
57
Q

Normal traits inherited by Multifactorial Inheritance

A
58
Q

Abnormal traits inherited by Multifactorial Inheritance

A
59
Q

Def of Non-Traditional Inheritance

A
  • Inheritance patterns which do not fall into the chromosomal, single gene, or multifactorial categories
60
Q

Examples of Non-Traditional Inheritance

A
  • Cytoplasmic inheritance
  • Mosaicism
  • Uniparental disomy