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G and H > X linked and Mitochondrial > Flashcards

X linked and Mitochondrial Flashcards

Week 7

1
Q

Sex-linked vs sex-limited inheritance

A

Sex-linked traits
-Only on sex chromosomes
-Dominant or recessive

Sex-limited
-Phenotype observed in 1 sex
-X-linked or autosomal

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2
Q

How do males and females express X-linked traits

A

M= Always express the trait (single X)

F= Can show dominant or recessive phenotype

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3
Q

X-linked dominant features

A

Affected father passes onto all daughters but no sons

50% chance that affected female (hetero) passes on

2:1 female: male

Severity (largest –> smallest) : homozygous female –> hemizygous male –> heterozygous females

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4
Q

X-linked recessive features

A

Knight’s move

Parents and children usually healthy

Affects mostly males as females have 2 X

½ chance subsequent brother impacted

½ chance sisters if affected boy impacted

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5
Q

What gene is involved in colour blindess?

A

Gene
-OPN1LW (yellow/orange)
-OPN1MW (yellow/green)

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6
Q

Is colour blindness X-linked recessive or dominant?

A

recessive

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7
Q

Is Hypophosphatemic rickets X-linked recessive or dominant?

A

dominant

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7
Q

gene affected in hypophosphatemic rickets

A

PHEX gene

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8
Q

incidence of rickets

A

1/ 20 000 newborns

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9
Q

colour blindness incidence

A

1/2 males
1/200 females

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10
Q

What is the normal gene and gene products of Duchenne Muscular Dystrophy?

A

DMD gene

produces dystrophin (under sarcolemma, critical structural protein)

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11
Q

Is Duchene Muscular Dystrophy recessive or dominant?

A

recessive

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11
Q

Who does DM dystrophy mainly affect and why?

A

Affects mainly males
(females protected by second X but still vulnerable to cardiac muscle weakness)

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12
Q

Clinical features of Dm Dystrophy

A

Gower’s maneuverer to raise

Pseudohypertrophy of calf muscles

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13
Q

Progression of DM Dystrophy

A

normal 1-3yrs
-wheelcahirs 10-12
-death 20

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14
Q

What is the most common cause of death for patients with DM dystrophy?

A

cardiac muscle/ respiratory failure

15
Q

potential therapies for DM dystrophy

A

Exon skipping

Reading through STOP codon

16
Q

What are the two type of haemophilia and what genes impact them?

A

A= F8 gene (clotting factor VIII deficiency)

B= F9 gene (clotting factor IX deficiency)

17
Q

Old and new treatments of Haemophlia

A

Old
-blood trans
-infuse anti-haemophilic factor

New
-recombinant clotting factors

18
Q

Why is haemophilia A more serious?

A

A is more serious
-clotting factor VII affects both intrinsic and extrinsic pathways

19
Q

Affected gene and mutation of Kennedy’s disease

A

Gene
AR
Mutation
CAG repeats greater than 35 in AR protein

20
Q

Clinical features of Kennedy’s disease

A

Toxic motor neurons
-spinal and bulbar muscle atrophy

Progressive muscular atrophy of motor neurons in spinal cord

21
Q

What group of those with Kennedy’s Diseases is usually asymptomatic?

A

Heterozygous females

protected by X

22
Q

What does mitochondrial encode for and how is it stored?

A

Store
-As a single circular chromosome

Encode
-Ribosomes and OXPHCS proteins

23
Q

heteroplasmy

A

cell or organism in which ALL copies of mitochondiral DNA are NOT the same

24
Q

homoplasmy

A

mitochondrial genome are EXACTLY the same

25
Q

How does heteroplasmy relate to disease penetrance?

A

proportion of mutant disease copies determines penetrance and expressivity

26
Q

What is the gene affected in Leigh Disease and what does it cause?

A

Gene
MTATP6
(encodes ATP synthase 6)

Deficiencies in ATP production and oxidative phosphorylation
27
Q

what are the X-linked recessive diseases?

A

Kennedy’s Disease
Haemophilia
DM Dystrophy
Colour blindness

28
Q

Compare mutations on X chromsomes for males vs females.

A

Expression
-male always

Severity
-male more as females may mask

carrier
-only females

compensation
-females have x-inactivation

inheritance
-X from mother, passes to daughter (male)

29
Q

Describe the inheritance of X-linked mutations for females vs males

A

females
-one X from each parent

males
-X from mother
-passes onto daughter

30
Q

Compare mitochondrial and autosomal inheritance.

A

Location
M= mitochondira
A= Autosomes

Inheritance pattern
M= maternal
A= both

Penetrance and expression
M= maternal lineage, varies in severity
A= more varible as more genes present

31
Q

Examples of mitochondrial inheritance

A

Leber’s Hereditary Optic Neuropathy, MELAS syndrome

32
Q

What types of disorders can mitochondrial inheritance lead to?

A

affect energy production

G and H (16 decks)

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