How Mutations Affect Health and Craniofacial Development Flashcards
How many de novo mutations are children normally born with that were not present in the parents?
100-200
Rate of children born with a diagnosable genetic condition that can be attributed to a single major mutation?
1 in 50
What is aneuploidy?
aberration in chromosome number caused by faulty segregation of chromosomes during mitosis or meiosis
Ratio of babies born with aneuploidy
1 in 400
Where does aneuploidy most commonly occur?
in female meiosis 1
-increased risk with maternal age
Examples of aneuploidy with oral manifestations:
-down syndrome
-edwards syndrome
-mosaic 22 trisomy
-turner syndrome
-etc
What is down syndrome?
trisomy 21
-full or partial extra chromosome 21
-in in 700 babies in the US
-most common chromosomal condition
What causes trisomy 21?
-nondisjunction >95% of cases
-mosaicism around 1% of cases: least common form
-translocation around 4% of cases
What is the only factor that has been associated with increased chance of having baby with Down syndrome?
maternal age
-however this is not always a good indicator
is heredity a factor in trisomy 21?
no not really
(1% of cases)
Signs of down syndrome:
-low muscle tone
-small stature
-cognitive delay
-transverse palmar crease
What are the three things you must ask being treating a patient with Down syndrome?
-do they have any heart defects
-do they have any spinal problems
-do they have seizures
Individuals with Down syndrome are at risk for:
-heart defects
-spinal problems atlantoaxial instability)
-GI defects
-immune disorders
-sleep apnea
-obesity
-leukemia
-dementia
-endocrine problems
-dental problems
-seizures
What causes chromosomal rearrangments?
chromosome breakage or by recombination between mispaired chromosomes during meiosis
What type of chromosomal rearrangements cause disease?
those that change copy number of genes or that break up an important gene
Examples of things caused by chromosomal rearrangement with oral manifestations:
-cri-du-chat
-prader-willi
-williams syndrome
-angelman syndrome
Signs for cri-du-chat:
-intellectual disability and delayed development
-small head size
-low birth weight
-weak muscle tone
-transverse palmar crease
-some have heart defects
-Cats cry
Facial features of cri-du-chat:
-widely set eyes
-low set ears
-small jaw
-rounded face
-epicanthal folds
-broad nasal bridge
-downward slanting palpebral fissues
What are single gene disorders?
mutations in single gene
-can be dominant or recessive
What are multifactorial genes?
caused not by a single major mutation but by interacting genetic and environmental risk factors
-most common forms of diseases are multifactorial
What does the median palatal plate form?
primary palate
What does nasal septum form from?
from the frontonasal prominence
What does palatal shelf form from?
maxillary process of the first pharyngeal arch
What does the secondary palate do?
separate the nasal cavity from the oral cavity
What is the secondary palate needed for?
swallowing, taste, vomiting, breathing, and speech
What is one of the most common birth defects in humans?
cleft lip/palate
What percent of cleft palate come form a syndromic cause?
30%
What percent of cleft palate come from a non-syndromic cause?
70%
What are some causes of cleft palate?
environmental: alcohol, phenytoin, retinoic acid, radiation
nutrutional/metabolic: low methionine, low folic acid, maternal DM
genetic: 350+ mendelian disorder, chromosomal aberrations
can cleft lip be caught early in development?
no- technology does not exist to easily detect facial abnormalities during prenatal screening
etiology of cleft palate is…
multifactorial
