Genetics and Chromosomal Flashcards
risk of autosomal dominant disease for child with 1 affected parent
50% risk
risk of autosomal recessive disease for child with 1 affected parent
25% risk
risk of X-linked recessive disease for child when mother is carrier
50% of her daughters can be carriers
50% of her sons can be affected
50% of her offspring can be normal
25% of her offspring will manifest the disease
Etiology of Down Syndrome
trisomy of chromosome 21; maternal non-disjunction; associated with advanced maternal age
Down Syndrome Prenatal Screening Tests
quad screen: alpha fetoprotein, estriol, Hcg and inhibin A
Down syndrome hands and feet
hand: clindoactyly, single flexion crease (Simian crease), short broad hands, shortened 5th phalynx
feet: wide spaced 1st/2nd toes (“sandle toes”)
Facial characteristics of Down Syndrome
flattened face, epicanthal folds, big tongue (macroglossia), small chin (micrognathia), low set ears
Newborn with possible Down Syndrome must have ______ done before discharge.
ECHO
Neuro effects of Downs
mental retardation (mild/mod), seizures (5-10%), early Alzheimer’s and dementia (30-40yo)
Results of prenatal quad screen in Downs
Low Alpha Feto Protein
Low Unconjugated estriol
Elevated hCG
Elevated Inhibin A
Cardiac effects of Downs
50% with cardiac anomalies (ASD most common); need ECHO!!!
HEENT effects of Downs
Hearing loss, ET dysfunction (recurrent otitis media, sinusitis), early cataracts and glaucoma, Brushfield spots
trisomy 18 is called __________ syndrome.
Edwards
Phenotypic features of trisomy 18
rocker-bottom feet, clenched hand w/ overlapping fingers, hypotonia, micropthalmia (small eyes), micrognathia
Prognosis of Edwards Syndrome
only 5% live past 1 year
Trisomy 13 is called _________ Syndrome
Patau
Features of Patau Syndrome
Polydactyly
Aplasia Cutis (missing patches of skin)
Cryptorchidism (no testes in scrotum)
Equinovarus deformities
Prognosis of trisomy 13
95% die by 6 months of age due to apneic spells
XXY (extra X chromosome) called _____.
Klinefelter Syndrome
Etiology of extra X chromosome
Non-disjunction in either the sperm or egg
Increased with advanced maternal age
Klinefelter most common genetic cause of _____ in men.
infertility
Signs of XXY
present as tall, thin, socially awkward adolescent male with mild mental delays
testosterone deficiency, small penis, hypogonadism, scant pubic hair, gynecomastia
Young female comes in with absence of menses. What to do?
Pregnancy test
r/o Turner Syndrome
Most common cause of inherited mental retardation in males is ______.
Fragile X syndrome