ABP Content Specs #2 D&E Biological Mechanisms in Dev & Beh Flashcards
Type of inheritance pattern for Huntington’s disease, NF-1, achondroplasia, familial hypercholesterolemia?
Autosomal dominant
each affected person usually has an affected parent; happens in every generation
Type of inheritance pattern for Tay-Sachs disease, sickle cell anemia, cystic fibrosis, phenylketonuria (PKU)?
Autosomal recessive
both parents of an affected person are carriers; not usually seen in every generation
Type of inheritance for Hypophosphatemic rickets (vitamin D resistant rickets), ornithine tanscarbamylase deficiency?
X-linked dominant
Females more frequently affected b/c all daughters and no sons of an affected man will be affected. Can have affected males and females in same generation if mom is affected.
Type of inheritance pattern for Hemophilia A, Duchenne muscular dystrophy?
X-linked recessive
Males more frequently affected. Affected males often present in each generation.
Genomic imprinting?
process by which maternally & paternally derived chromosomes are uniquely modified (usually by methylation) –> leading to different expression of a certain gene or genes on these chromosomes depending on their parental origin.
If genes are inactivated/silenced in the female line then it is maternally imprinted (ie. only the paternally derived allele is expressed/active).
If genes are inactivated/silence in the male line then it is paternally imprinted (ie. only the maternally derived allele is expressed/active).
Example of condition that is caused by loss of paternal copy of 15q11?
Prader-Willi syndrome (paternal copy loss or paternal imprinting).
Have loss of paternal copy of PWS critical region on ch 15q11.2-13
Example of condition that is caused by loss of maternal copy of 15q11?
Angelman syndrome due to loss of maternal copy of 15q11.2-13.3
Mitochondrial conditions are inherited maternally or paternally?
maternally b/c mitochondria are transmitted by ova and not sperm
Inheritance pattern of mutations in mitochondrial DNA?
- both males and females affected
- condition is transmitted through the female to her offspring
- if a male has the trait and his spouse doesn’t then their offspring won’t have the trait
I.e. an affected woman can pass the defective mitochondria ch to all of her children. But an affected man has little risk of passing the mutation to his child.
Tendency of certain genetic disorders for individuals in successive generations to present at an earlier age and/or with more severe manifestations?
Anticipation
Usually seen in conditions resulting from expression of a nucleotide repeat expansion that increases in size and have a more significant effect when passed from one generation to the next.
Most common X-linked disorder with triplet repeat instability and expansion?
Fragile X syndrome
Examples of diseases with anticipation?
Huntington’s disease
Myotonic dystrophy
Friedrich’s ataxia
Conditions that are contiguous gene disorders (i.e. clinical constellation of symptoms caused by deletion of a chromosome segment that has two or more adjacent genes)?
Williams syndrome
Smith-Magenis syndrome
22q11.2 deletion syndrome
Features of Williams syndrome?
-contiguous gene disorder that deletes gene for elastin & other neighboring genes on 7q11.23
-coarse, elf-like facies with upturned nose, full lips
-short stature
-congenital heart disease (supra-valvular aortic stenosis)
-hypercalcemia
-GDD, mostly have ID but STRONG language skills
-cocktail party personality/friendly
-attention problems
-anxiety
Features of Smith-Magenis syndrome?
-contiguous gene disorder with deletion on chromosome 17p11
-prominent forehead, deep-set eyes, cupid-shaped upper lip
-ID
-self-mutilating behaviors (head banging, wrist biting, onychotillomania - pulling out fingernails and toenails, polyembolokoilamania - inserting foreign body into orifices)
-sleep issues
Features of 22q11.2 deletion (Velocardiofacial syndrome or DiGeorge syndrome)?
-contiguous gene disorder
-hooded eyelids, ear anomalies, prominent nasal bridge, bulbous nose, micrognathia, asymmetric crying facies
-cleft palate
-heart defects (conotruncal cardiac defects like Tetralogy of Fallot)
-thymus hypoplasia leading to immune issues
-parathyroid hypoplasia leading to low calcium
What is Malformation?
morphological abnormality due to innate genetic defect (e.g. cleft lip)
What is Deformation?
distortion of bodily structures due to external physical force (e.g. oligohydramnios leading to micrognathia, talipes)
What is Disruption?
destruction of bodily structure due to external factor (e.g. amniotic bands leading to digit or limb amputation)
What is aneuploidy?
The occurrence of one or more extra or missing chromosomes in a cell or organism
ex. Trisomy 21/Down syndrome
What conditions are due to micro-deletion in chromosomes?
- prader-willi syndrome/Angelman syndrome in chromosome 15q11-13
- Smith-magenis syndrome (deletion of chromsome 17p11.2)
- DiGeorge/velo-cardio-facial syndrome: hemizygous deletion of chromosome 22q11.2
- Williams-Beuren syndrome: deletion of chromosomal region 7q11.2
- ATR-X syndrome: mutation in the ATR-X gene on the X-chromosome
What conditions are due to single gene defects?
- Barth syndrome (X-linked cardioskeletal myopathy and neutropenia): mitochondrial function impairments due to the TAZ gene on chromosome Xq28
- Fragile X syndrome: CCG repeat expanion on FMR1 gene
- ICF syndrome: mutation in the DNA methyltransferase 3B 9DNMT3B) gene on chromosome 20
- Neurofibromatosis: mutations or deletions in neurofibromin gene on ch 17q11.2
- Rett syndrome: mutations in the MECP2 gene on the X-chromosome
- Smith-Lemli-Opitz syndrome: mutations in the gene encoding sterol delta-7-reductase on chr 11q12-13
Trisomy 13 features?
-associated with advanced maternal age
-midline defects including cleft palate and holoprosencephaly
-cutis aplasia (don’t have extra layer of skin, just thin membrane esp scalp)
-microcephaly
-micro-opthalmia, ear anomalies
-IUGR/severe growth issues
-45% die in 1st month, 85% in first year
Trisomy 18 features?
-associated with AMA
-rocker bottom feet
-hypoplastic nails, clenched fists, overlap fingers
-microcephaly, prominent occiput
-micro-opthalmia, micrognathia, ear anomalies
-heart malformations
-horseshoe kidneys
-IUGR
-50% die in first week, 95% in first year