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Block 3 Genetic Disorders - Coggle Diagram
Block 3 Genetic Disorders
Autosomal Dominant
Marfan Syndrome
Clinical Signs
Cardiovascular lesions (aortic root valvular disease)
Ocular defects
MSK Abnormalities
tall slender, long arms
Disease Class: FBN1 = Fibrillinopathy
Neurofibromatosis
Clinical Signs
Iris Hamartomas (Lisch nodules)
Peripheral Neurofibromas
Optic pathway glioma
Multiple cafe-au-lait spots
Tibial hypoplasia
Plexiform Neurofibroma
Autosomal Dominant Polycystic Kidney Disease
Bilateral Retinoblastoma
Autosomal Recessive
SMA
Type 1 SMA
presents in early life as a floppy infant (death before 24 Mo)
X-linked
X-linked recessive inheritance
Conditions
DMD
Clinical Characteristics
Progressive Muscle Weakness
pseudohypertrophy of calves
Cardiomyopathy
Inheritance
Familial: mother is carrier
Sporadic: 2/3 females are carriers & 2/3 of these women have elevated CK levels (Creatinine Kinase)
General Guidlines:
In almost all instances, only males are affected
Risk for an affected male is 50% if mother is a carrier
Similar risk for having a carrier female offspring (50%) if mother is a carrier
Dominant
lethal gene is frequently in male so usually only females live to be affected
Offspring risk to an affected female is 1/3 since only females survive
Epigenetic disorders
Maternal/ Paternal
imprinting
on chromosome with paternal/ maternal deletion.
DNA methylation is involved in imprinting!
P
rader Willi
paternal deletion
, maternal imprinting w/ defect
Mechanisms of Prader-Willi Syndrome:
Paternal Deletion (70-75%) – A deletion of the paternal copy of the 15q11-q13 region.
Maternal Uniparental Disomy (UPD) (20-25%) – The child inherits two copies of chromosome 15 from the mother and none from the father.
Imprinting Defect (1-3%) – An error in imprinting that silences the paternal genes in this region.
Clinical Characteristics
Excessive eating & obesity, diffuse reduction in muscle tone, hypoplastic genitalia, poor feeding/ feeding through a tube, difficulty holding head-upright
Angel
m
an Syndrome
Clinical Characteristics
laughter
maternal deletion
, paternal imprinting w/ defect
Loss of function of meCP2 --> Reader of DNA methylation patterns
