Genetics final #2
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25 terms
Terms | Definitions |
|---|---|
 Common themes of aneuploidy (imbalance of chromosomal material) syndromes include: | -growth retardation: SGA, failure to thrive -neurologic impairment: MR, LD, sz's, microcephaly, hypotonia, psycho-emotional dysfunction -distinctive/dysmorphic features -CV malformations and other congenital anomalies -family hx of infertility or frequent miscarriage |
| What is array genomic hybridization? | -also called comparative genomic hybridization (CGH) -a method of examining multiple loci simultaneously to identify genetic imbalance |
| What is Down syndrome? | -trisomy 21, translocation involving long arm of chromosome -most frequently occurring chromosomal disorder in living humans -usually caused by an error in cell division called non-disjunction -incidence increases w/advancing maternal age |
| How does Down syndrome present? | -most commonly diagnosed at birth -also ascertained prenatally by amniocentesis when the pregnancy is felt to be "at risk" (AMA, ultrasound features, failed serum screen) |
| How is the diagnosis made for down syndrome? | -clinically usually by facial gestalt -karyotype analysis is not typically used to make or confirm the diagnosis, but to "rule out" inherited forms which carry a significantly higher recurrence risk |
| How do you manage down syndrome? | -make the diagnosis and provide counseling prior to nursery discharge -identify congenital heart dz -provide education on neonatal feeding and nutrition -identify down syndrome caused by a translocation |
| What is turner syndrome? | -affects approx 1 out of every 2500 female live births -gonadal dysgenesis and short stature |
| What causes turner syndrome? | -loss of part or all of the second gender determining chromosome -genes found on X and Y are key to normal linear growth and development of the gonads |
| How does Turner syndrome present? | -in the neonatal period with the findings of coarctation of the aorta or peripheral lymphadema |
| How is turner syndrome diagnosed? | -through clinical features initiate suspicion -diagnosis made on a cytogentic basis |
| What are the managment issues with turner syndrome? | -echo to screen for left sided heart defects, including progressive aortic root dilation -maintain a low threshold to screen for Y chromosome mosaicism (SRY-FISH) -treatment for estrogen and growth hormone deficiency |
| What is klinefelter syndrome? | -males have an extra X chromosome (47 total chromosomes) Principal effects are hypogonadism and impaired fertility -other physical characteristics vary widely: little to no signs, to lanky, youthful build and facial appearance, rounded body type gynecomastia |
| What is the biologic basis of klinefelter syndrome? | -like females, only one X chromosome is fully functional in any given cell- the rest are inactivated at the DNA level. Even inactive X chromosomes have gene expression occurring at the top and bottom ends of the chromosomes. Because of this, those 2 regions are known as the pseudo-autosomal regions. |
| What are the most common presentations of klinefelter syndrome? | -47 XXY can be found in boys being worked up for fragile X syndrome -male infertility, delayed pubertal development |
| How do you diagnose klinefelter syndrome? | -cytogentic basis |
| What are the important management issues with klinefelter syndrome? | -treatment and counseling for infertility -treatment for testosterone deficiency -monitor for leg ulcers, breast ca, mitral valve prolapse -neurobehavioral/cognitive assessment/intervention when appropriate |
| What is thought to cause the conditions of partial chromosome imbalances? | -mechanism underlying the deletion is thought to be unequal meiotic recombination |
| What is velocardiofacial syndrome? | -chromosome 22q11 deletion syndrome, because of the wide variety of presentations, this condition has been called by many different names including shprintzen and digeorge syndrome |
| How does velocardiofacial syndrome present? | -by karyotype (FISH) from amniocentesis when a fetal heart defect is ascertained -newborns with the presentation of the DiGeorge or Robin anomaly -present with typical facial features, speech delays or nasal speech -in adulthood, after an affected child is diagnosed |
| How do you diagnose velocardiofacial syndrome? | -FISH probe of chromosome 22q11.2 |
| How do you manage velocardiofacial syndrome? | -identify cognitive heart disease -determine if either parent is affected |
| What is williams syndrome? | -neurodevelopmental disorder with a distinctive "elfin" facial appearance and personality, cardiovascular anomalies and hypercalcemia -deletion 7q11.2 |
| How does Williams syndrome present? | -infants and children with supravalvar aortic stenosis -children with typical facial features and the classic neurocognitive phenotype |
| How do you diagnose Williams syndrome? | -clinical features raise suspicion -FISH probe of chromosome 7q11.23 is utilized |
| How do you manage Williams syndrome? | -identify congenital heart disease -identify hypercalcemia -identify renal calcinosis |
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