PCOL 838 GENETIC DISEASES II PART 2
EXAM 2025 QUESTIONS AND ANSWERS
Osteogenesis imperfecta is a _____ (homogeneous/heterogenous) disease caused by mutation
to genes involving type 1 collagen formation
Heterogenous
Osteogenesis imperfecta is an autosomal _____ (recessive/dominant) inheritance due to
haploinsuffieciency or dominant negative mutants
Dominant
Type 1 OI is a mild autosomal dominant mutation that is ______ (amorphic, antimorphic, etc)
that leads to short stature, postnatal fractures, bleu scleras, and hearing loss
Amorphic-> normal but reduced collagen (haploinsufficiency)
Type 2 OI is a perinatal lethal sporadic autosomal dominant mutation that is _____ (amorphic,
antimorphic, etc) that leads to sever prenatal fracture, abnormal bone formation, severe
deformities, blue scleras, connective tissue fragility)
Antimorphic -> abnormal collagen
Type 3 OI is a progressive deforming autosomal dominant mutation that is (amorphic,
antimorphic, etc) that leads to prenatal fractures, deformities usually present at birth, very
short stature, usually nonambulatory, blue scleras, hearing loss
Mild antimorphic
Type 4 OI is a deforming with normal scleras autosomal dominant mutation that is
___(amorphic, antimorphic, etc) that leads to postnatal fractures, mild-moderate deformities,
premature hearing loss, normal or gray scleras, dental abnormalities
Mild antimorphic
Type 1 OI has a ___% decrease in type 1 collagen formed
50
1 @COPYRIGHT THESTAR 2025/2026
, Type 2 OI has a ___% decrease in type 1 collagen formed
75
Type 2 OI is ___ (more/less) severe than type 1
More
Type 1 OI is an amorphic mutation to the ___ gene and in the ____ region
COL1A1; promoter
Nonsense (stop-gain) mutation in type 1 OI causes _____ decay of transcription
Nonsense mediated
The phenotype of type 1 OI is caused by insufficient amount of ____
Protein
Type 2 OI antimorphic mutation to either ___ or ___ gene
COL1A1 or COL1A2
Type 2 OI is ___ (always/never) inherited
Never, its often embryonic lethal
Type 2 OI may appear to be autosomal recessive due to _____
Gonadal mosaicism
What is phenylketonuria (PKU)? Is it recessive or dominant?
-An inborn error of metabolism with elevated levels of urinary phenylpyruvate and
phenylacetate
-Loss of function mutation to the phenylalanine hydroxylase (PAH) gene
-Circulatory Phe concentration of 0.06 mM to 0.1 mM
-Autosomal recessive
What is hyperphenylalaninemia in terms of circulatory phenylalanine concentration?
>1.2 mM
PKU means that your body cannot convert phenylalanine to what?
Tyrosine
What is the dietary restriction treatment for PKU?
-Low Phe formula mixed with breast milk to maintain [Phe] below 1 mM (benign
hyperphenylalaninemia)
-Dietary restriction should be continued indefinitely
2 @COPYRIGHT THESTAR 2025/2026
EXAM 2025 QUESTIONS AND ANSWERS
Osteogenesis imperfecta is a _____ (homogeneous/heterogenous) disease caused by mutation
to genes involving type 1 collagen formation
Heterogenous
Osteogenesis imperfecta is an autosomal _____ (recessive/dominant) inheritance due to
haploinsuffieciency or dominant negative mutants
Dominant
Type 1 OI is a mild autosomal dominant mutation that is ______ (amorphic, antimorphic, etc)
that leads to short stature, postnatal fractures, bleu scleras, and hearing loss
Amorphic-> normal but reduced collagen (haploinsufficiency)
Type 2 OI is a perinatal lethal sporadic autosomal dominant mutation that is _____ (amorphic,
antimorphic, etc) that leads to sever prenatal fracture, abnormal bone formation, severe
deformities, blue scleras, connective tissue fragility)
Antimorphic -> abnormal collagen
Type 3 OI is a progressive deforming autosomal dominant mutation that is (amorphic,
antimorphic, etc) that leads to prenatal fractures, deformities usually present at birth, very
short stature, usually nonambulatory, blue scleras, hearing loss
Mild antimorphic
Type 4 OI is a deforming with normal scleras autosomal dominant mutation that is
___(amorphic, antimorphic, etc) that leads to postnatal fractures, mild-moderate deformities,
premature hearing loss, normal or gray scleras, dental abnormalities
Mild antimorphic
Type 1 OI has a ___% decrease in type 1 collagen formed
50
1 @COPYRIGHT THESTAR 2025/2026
, Type 2 OI has a ___% decrease in type 1 collagen formed
75
Type 2 OI is ___ (more/less) severe than type 1
More
Type 1 OI is an amorphic mutation to the ___ gene and in the ____ region
COL1A1; promoter
Nonsense (stop-gain) mutation in type 1 OI causes _____ decay of transcription
Nonsense mediated
The phenotype of type 1 OI is caused by insufficient amount of ____
Protein
Type 2 OI antimorphic mutation to either ___ or ___ gene
COL1A1 or COL1A2
Type 2 OI is ___ (always/never) inherited
Never, its often embryonic lethal
Type 2 OI may appear to be autosomal recessive due to _____
Gonadal mosaicism
What is phenylketonuria (PKU)? Is it recessive or dominant?
-An inborn error of metabolism with elevated levels of urinary phenylpyruvate and
phenylacetate
-Loss of function mutation to the phenylalanine hydroxylase (PAH) gene
-Circulatory Phe concentration of 0.06 mM to 0.1 mM
-Autosomal recessive
What is hyperphenylalaninemia in terms of circulatory phenylalanine concentration?
>1.2 mM
PKU means that your body cannot convert phenylalanine to what?
Tyrosine
What is the dietary restriction treatment for PKU?
-Low Phe formula mixed with breast milk to maintain [Phe] below 1 mM (benign
hyperphenylalaninemia)
-Dietary restriction should be continued indefinitely
2 @COPYRIGHT THESTAR 2025/2026
