x-linked pattern Flashcards
What is the manifestation of Duchenne Muscular Dystrophy?
Enlarged calves and wasting of the thigh muscle
For men, tends to be lethal before age of 30
Duchenne muscular dystrophy has high or low reproductive fitness
Low
Difference between Duchenne and Becker muscular dystrophy
Less severe mutation in DMD leads to Becker
More severe mutation in DMD leads to Duchenne
When a child is affected, look for the disorder in maternal relatives. Which mode of transmission is this?
X-linked recessive
What is manefestation of hemophilia A
inherent deficiency of clotting factor 8, resulting in increased tendency to bleed
Relationship between hemophilia A and allelic heterogeneity
Inversion of intron lead to incorrect splicing
while other mutation leads to hemophilia A
How is Duchenne muscular dystrophy transmitted?
X-linked recessive
How is Hemophilia A transmitted?
X-linked recessive
What causes X-linked SCID and what is the manifestation?
Due to defect in SCIDX1 gene, it leads to defect in gamma chain of receptor for several interleukins(IL2RG), which result into immature T-cell. This results in a deficiency of normal B-cell function.
What happens if a woman who is carrier of Duchenne have a symptoms? How can it be explained?
It is due to skewed X-inactivation. The number of cells that contain the active X chromosome with the mutation in DMD are larger than cells that contain the active X with functional DMD gene.
How is red/green color deficiency transmitted?
X-linked recessive
How is Rett syndrome transmitted?
X-linked dominant
What mostly happens to males who have X-linked dominant disorder?
Die in utero
What is Rett syndrome?
Genetic brain disorder
Manifestation of incontinentia pigmenti
rashes and blisters in early life and later, patches of hyperpigmentation
How is incontinentia pigmenti trasmitted?
X-linked dominant
Transmission of vitamin D resistant Rickets
X-linked dominant
How can it be explained if a person who have inherited the mutant allele of autosomal dominant disorder does not display the disease phenotype?
A disorder is non-penetrance
What incomplete penetrance?
Penetrance may be dependent on age, (adult onset disease),
How do we calculate recurrence risk based on penetrance of 80% for autosomal dominant disease?
recurrence risk normal is 50%, so 50*80 / 100 = 40%.
So recurrence risk is 40% when penetrance is 80%
What does variable expression mean?
severity of genetic disease is different due to some factors
What are 3 factors affecting variable expression
- Random chance
- Other genetic factors or sex influence
- Environmental exposure
How is variable expression related to Hemochromatosis?
It is more severe in male , and premenapausal females will menstruate and lose iron.
What is hemochromatosis and mode of transmission?
an iron overload disorder (autosomal recessive)
