When can amniocentesis be done?
16 weeks
What is used to track intrauterine growth over time?
Fetal US
When are structural anomalies (like myelomeningocele) best detected on US?
Between 12-24 weeks gestation
What maternal problem can be a complicating factor that blunts the accuracy of US findings?
Maternal obesity
What 3 hematologic diseases can be diagnosed prenatally?
Factor 8 deficiency, factor 9 deficiency, sickle cell disease
What is monogenic inheritance?
Genetic disorders caused by a mutation in one gene
What is multifactorial inheritance?
Genetic disorders caused by mutations in multiple genes
What is epigenetics?
Genetic disorders caused by a combination of gene mutations and environmental factors
In which inheritance pattern are males affected and females carriers?
X-linked recessive
If there are any female relatives with a disorder, which inheritance pattern is eliminated?
X-linked recessive
Is male-to-male transmission possible in X-linked recessive disorders?
No
If a question casually mentions a kid who had two uncles with a similar problem, what should you think?
You know that only males are affected…pointing towards an X-linked recessive disorder
Which type of inheritance disorders frequently involve an enzyme deficiency?
X-linked recessive
Name 8 frequently tested X-linked recessive conditions
When will you see a phenotypic female, but genetic male and what is the inheritance pattern of this disorder?
Androgen insensitivity (X-linked recessive)
Mom is known carrier of an X-linked recessive disorder…chances of affected male, female carrier, affected children?
Males: 50% affected, 50% not affected
Females: 50% carriers, 50% not carriers
Children: 25% carriers, 25% disease, 50% normal
For X-linked dominant disorder, Dad has gene on his X chromosome, which kids have disease?
For X-linked dominant disorder, Mom has gene on one of her X chromosomes, which kids affected?
50% of her kids will have it and 50% won’t
Are there carriers for an X-linked dominant disease?
No
Which other inheritance pattern is the same as X-linked dominant?
Autosomal dominant…makes it very difficult to distinguish
How are mitochondrial disorders transmitted?
Exclusively through mothers
*Mother and mitochondria both start with an M
Which disorders have no male to male transmission?
X-linked disorders (recessive or dominant)
Name 4 X-linked dominant conditions to consider (remember, not too many of them and they will most likely not ask you to pick this up from question)
What is the only way a disease can be transmitted from father to son?
Autosomal dominant inheritance