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Genetics > Lecture 5 - Monogenic Inheritance > Flashcards

Lecture 5 - Monogenic Inheritance Flashcards

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Biology 101 flashcards
1
Q

Monogenic

A
  • one gene governs a particular trait
  • discontinuous variation
  • high penetrance
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2
Q

Polygenic

A
  • many genes affect one trait
  • continuous variation
  • low penetrance
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3
Q

Monogenic Disorder

A
  • disorder caused by defect in one gene

- inherited by Mendilian Inheritance

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4
Q

Multiple Allealism/Alleilic Heterogenity

A
  • many different allelles on the same locus are capable of causing disease
  • example: CF
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5
Q

Locus Heterogenity

A
  • many different loci are capable producing the same disease

- example: Retinitis Pigmentosa

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6
Q

Genetic Hetereogenity

A

-single disease can be manifested by different genetic mechanisms/diff genes at diff loci

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7
Q

Pleiotrophy

A

-single gene capable of causing multiple traits

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8
Q

AD main features

A
  • expressed in both Hetero + homozygotes
  • on average -> half offspring affected (equally amongst men and women)
  • paternal age ->correlated with freq of new mutation
  • variable penetrance + expressivity
  • vertical degree pattern
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9
Q

What does AD usually affect

A
  • structural proteins
  • carriers
  • receptors
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10
Q

AD Diseases

A

1) Achondroplasia
2) Marfans
3) Osteogenesis Imperfecta
4) Familial Hypercholestremia
5) Huntington’s

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11
Q

Achondroplasia

A

-defect in FGFR-3

> normally has neg affect on bone growth –> makes it constinutively active

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12
Q

Marfan Syndrome

A

-FBN1 gene ->defect in Fibrillin 1 –>defective Microfibrils of ECM

-CT disorder affecting:
> Eye
> Skeletal
> CV

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13
Q

Familial Hypercholestremial

A

-defect in LDL-R –> high amount of LDL–> Xanthomas+ Arthemas

  • Multiple Allelism/Allelic Heterogenity
  • Locus Hetereogenity
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14
Q

Difference in Homo and Hetero in Familial Hypercholestremia

A

Homo -> die of MI at 30

Hetere -> Coronary A disease by 40

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15
Q

Osteogenesis Imperfecta

A
  • mut in COLIA (produces Collagen 1)
  • brittle bones + blue sclera + deafness

*PLEIOTROPHY -> variable expressivity

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16
Q

Huntington

A
  • CAG repeat in huntington gene –> Glu residues –> caspase cleaves that shit –> toxic
  • # of repeats = severity/onset
17
Q

AR Main features

A
  • only in Homo
  • Freq + Severity equal in each sex
  • Horizontal pedigree -> single generation is affect (parents no)
18
Q

What does AR affect

A

-enzymes

19
Q

Diseases that are AR

A

1) PKU
2) CF
3) CBAVD
4) AR Deafness
5) Xeroderma Pigmentosum
6) Albinism
7) Sickle Cell Anemia
8) Tay-Sachs

20
Q

Albinism

A
  • defect in Tyrosinase

- no tyrosine -> melanin

21
Q

PKU

A
  • defect in PAH
  • PA is an essential AA
  • no PAH -> excess PA + PA-ketones
22
Q

Problems with PKU

A 
Brain Damage:
 > inhibit NT synthesis
 > AA transport
 > lack of neuronal development
 > defective myelin synthesis

Decr Pigmentation

23
Q

How to detect PKU

A

Guthrie Test

24
Q

AR Deafness

A
  • defect in Connexin 26 (GJB2)

- Connexin imp in K+ Hemostasis in the Cochlea of the Inner Ear

25
Q

CF

A
  • 1/25 white people carry the mutated allele
  • abnormal Cl- channel
  • F508 -> deletion of PA 508)

*Allelic Heterogeneity/Multiple allelism

26
Q

CBAVD

A
  • occurs in many CF

- Non-coding region of CFTR (intron 8 with thymidine tracts- 5T/7T/9T)

27
Q

AR Diseases and Natural Selection

A

-certain monogenic AR diseases have been affected by selective pressures that favour their phenotype

CF Carrier -> CHolera
Sickle Cell -> Malaria
Tay-Sachs -> TB

28
Q

Tay-Sachs

A
  • also called Gangliosidosis (enzyme = hexoaminodase)

- > found in neurons + glial cells –> accumulation of Ganglioside GM2 in lysosomes –> Neurodegen

29
Q

Sickle Cell Anemia

A

Hb Beta chain affected
->point mutation from CAG -> CTG -> 6th aa from GLU to VAL

Pleiotrophy

30
Q

Disease that is AR + AD

A

POLYCYSTIC KIDNEY

AR: mutation of Fibrocystin (PKHD1)
AD: Mutation of Polycystin 1/2 (PKD1/2)

  • shows locus hetereogenity
  • mech same in AR/AD

Genetics (9 decks)

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