Chromosomal Abnormalities

Question 1

Fragile X Syndrome

Answer 1

XL defect of methylation (trinucleotide repeat CGG) of FMR1 gene - codes for FMRp involved in mRNA translation for axons of brain and testes. 2nd most common genetic cause of ID after Down. eXtra large testes, jaw, ears

Question 2

Down Syndrome 6 Associated Diseases

Answer 2

Duodenal atresia
Hirschsprung ds
ASD
AD (Chr 21 codes for amyloid precursor prot)
Increased risk of ALL and AML

Question 3

Down Syndrome 3 Genetic Causes

Answer 3

95% meiotic nondisjunction
4% Robertsonian translocation
1% mosaicism (no maternal association)

Question 4

Down Syndrome 1st Trimester US and 2nd Trimester Quad Screen

Answer 4

US: Nuchal translucency

Quad Screen: Decreased AFP, Increased hCG, Decreased Estriol, Increased inhibin A

Question 5

Edwards Syndrome (what it is, findings, and quad screen + another)

Answer 5

Trisomy 18
Severe ID, rocker bottom feet, micrognathia, low set ears, clenched hands, prominent occiput, death usually within 1 year
Decreased AFP, hCG, Estriol, and normal (maybe decreased) inhibin A
PAPP-A also decreased along with hCG in 1st trimester

Question 6

Patau Syndrome (what it is and 1st trimester screen)

Answer 6

Trisomy 13, had severe ID and small stuff/rocker bottom, but also cleft liP/Palate and holoProsencephaly and Polydactyly. Death usually within 1 year
Decreased hCG, PAPP-A and increased nuchal translucency

Question 7

Cri-du-chat syndrome

Answer 7

Congenital microdeletion of short arm of chromsome 5 (46 chromosomes but 5p-)
Severe ID but high pitched crying/mewing

Question 8

Williams Syndrome

Answer 8

Microdeletion of long arm of chromosome 7

Will Ferrell in Elf - “Elfin” facies, ID, well-developed verbal and EXTREME friendliness with strangers

Question 9

22q11 Deletion Syndromes

Answer 9

Aberrant development of 3rd and 4th branchial pouches, so Cleft palate, Thymic aplasia, cardiac defects, and hypocalcemia (from parathyroid aplasia)
DiGeorge syndrome - thymic, parathyroid, and cardiac defects
Velocardiofacial - palate, facial, cardiac defects

Question 10

Klinefelter Syndrome

Answer 10

47XXY - basically a male with lots of feminine features, testicular atrophy, gyncomastia, female hair distribution. Has Barr body. Often comes up in infertility. Decreased inhibin so increased FSH. Decreased T and increased LH and E

Question 11

Turner Syndrome

Answer 11

45XO so female. Have super short stature, streak ovary, and webbed neck. Common cause of primary amenorrhea and no Barr body. Decreased E leads to increased LH and FSH

Question 12

Double Y Male

Answer 12

XYY, generally pretty normal and normal fertility. May be tall, have bad acne, and be associated with learning disability/antisocial/autism spectrum