Exam Review 2020 Flashcards
(81 cards)
Characteristics of autosomal dominant inheritance (3)
1) variable expressivity
2) reduced penetrance
3) de novo mutations can occur and are associated with advanced paternal age
Concepts related to autosomal recessive inheritance (4)
1) 2 mutated copies are necessary
2) consanguinity may be present
3) ethnic predispositionmay be present
4) Less clinical variability than autosomal dominant disorders
Concepts related to X-linked recessive inheritance (3)
1) absence of male to male transmission
2) Males much more likely than females to be affected
3) All daughters of an affected male are carriers
Concepts related to X-linked dominant inheritance (3)
1) Females are much more likely than males to be affected
2) All daughters of an affected male are affected
3) Male to male transmission is not observed
reasons why females may show signs of an X-linked disorder
Skewed” X-inactivation (in some or all tissues) may lead to symptomatic “carriers”
MtDNA is only obtained from ____ (parent)
Mother
Heteroplasm vs homoplasmy (mitochondria)
Heteroplasmy: mixture of normal and abnormal mtDNA
Homoplasmy: all mtDNA is the same (normal or abnormal)
Treshold effect
A certain percentage of abnormal mtDNA is tolerated without symptoms
Random drift
The percentage of abnormal mtDNA can change over time, in different tissues
The increase in severity or earlier onset of a phenotype in successive generations
Anticipation
Can we predict when a trinucleotide repeat will expand?
No. They do not necessarily expand in every division
Gonadal mosaicism is important for recurrence risk assessment for apparently ________ disorders
de novo dominant
How does gonadal mosaicism affect individual?
It does not, only offspring
Gonadal Mosaicism mechanisms include (3)
- Uniparental disomy
- Heterozygous deletion
- Mutation
Prader-Willi Syndrome
1) Features: hypotonia, intellectual disability, hyperphagia (pathological overeating)
2) Caused by lack of expression from genes in the critical region that are normally only expressed from the paternal allele
Angelman Syndrome
Features: severe intellectual disability, movement disorder, seizures
Caused by lack of expression from genes in the critical region that are normally only expressed from the maternal allele.
______of newborns have a major anomaly
2-3%
______of newborns have a minor anomaly
15%
______% infant deaths & ______% deaths after neonatal period are attributed to major anomalies
20-30% infant deaths & 30-50% deaths after neonatal period
_____% newborns have single minor malformations, _____% of these have a major
13.4% newborns have single minor malformations, 3% of these have a major
_____% newborns have two minor ones, _____% of these have a major
0.8% newborns have two minor ones, 11% of these have a major
____% newborns have three or more w/___% chance of a major anomaly or intellectual disability
0.5% newborns have three or more w/ 20% chance of a major anomaly or intellectual disability
Cleft lip/ cleft palate
is a ____ anomaly.
Major
Congenital heart disease is a ____ anomaly
Major
