Biochem15

Question 1

Down syndrome is trisomy ___.

Answer 1

21 (1:700)

Down’s - Drinking age - 21

Question 2

What are some characteristic findings in trisomy 21?

Answer 2

Simian crease
Duodenal atresia
Congenital heart dz
INcreased risk for ALL & Alzheimer's (>35 y/o)
Prominent epicanthal folds
Gap btwn 1st 2 toes

Question 3

95% if trisomy cases are due to what?

Answer 3

Meiotic nondisjunction of homologous chromosomes

Question 4

Trisomy 21 is associated with advanced maternal age. 1:___ in women 45.

Answer 4

1:1500 45

Question 5

4% of trisomy 21 cases are due to what?

Answer 5

Robertsonian translocation

Question 6

In trisomy 21 cases what are the results of the pregnancy quad screen?

Answer 6

DECREASED: alpha-fetoprotein & estriol

INCREASED: beta-hCG & inhibin A

Question 7

What does ultrasound show in trisomy 21 cases?

Answer 7

INcreased nuchal in first trimester translcency

Question 8

Edwards’ syndrome is trisomy ___.

Answer 8

18 (1:8000)

Edwards - Election age - 18

Question 9

What are the findings in Edwards’ syndrome (trisomy 18)?

Answer 9

Severe mental retardation
rocker-bottom feet
Micrognathia (small jaw)
Low-set Ears
Clenched hands
Prominent occiput
congenital heart dz

Death usually occurs within 1 year of birth

Question 10

In trisomy 18 cases what are the results of the pregnancy quad screen?

Answer 10

DECREASED:

• alpha-fetoprotein
• beta-hCG
• estriol

NORMAL: inhibin A

Question 11

Patau’s syndrome is trisomy __.

Answer 11

13 (1:15,000)

“Patau - Puberty - 13”

Question 12

What are the findings in Patau’s syndrome (trisomy 13)?

Answer 12

Severe mental retardation
rocker-bottom feet
micropthalmia
microcephaly
cleft liP/Palate
holoProsencephaly
Polydactyly
congenital heart disease

Death usually occurs within 1 year of birth

Question 13

What are the results of first-trimester pregnancy screen in Patau’s syndrome cases?

Answer 13

DECREASED:

• beta-hCG
• PAPP-A

INCREASED:
- nuchal translucency

Question 14

What is Robertsonian translocation?

Answer 14

Nonreciprocal chromosomal translocation that commonly involves chromosome pairs 13,14,15,21,22

One of the most common types of translocations

Question 15

When do Robertsonian translocations occur?

Answer 15

When long arms of 2 acrocentric chromosomes fuse at the centromere and the 2 short arms are lost

Question 16

What are an acrocentric chromosomes?

Answer 16

chromosomes with centromeres near their ends

Question 17

In Robertsonian translocations, do balanced or unbalanced translocations result in miscarriage, stillbirth, and trisomies?

Answer 17

Unbalanced

Balanced normally do not cause any abnormal phenotypes

Question 18

What causes Cri-du-chat syndrome?

Answer 18

Congenital microdeletion of short arm of chromosome 5

46,XX or XY, 5p-

Question 19

What are the findings in Cri-du-chat syndrome?

Answer 19

Microcephaly
mod-severe retardation
High pitched crying/mewing
epicanthal folds
cardaic abnormalities (VSD)

“Cri du chat = cry of the cat”

Question 20

What syndrome is associated with a congenital microdeletion of long arm of chromosome 7?
What gene is in the deleted region?

Answer 20

Williams syndrome

elastin gene

Question 21

What are the findings in WIlliams syndrome?

Answer 21

"Elfin" facies
Intellectual disability
hypercalcemia (INcreased sensitivity to Vit. D)
Well-developed verbal skills
Extreme friendliness w/ strangers
cardiac abnormalities

Question 22

What are the potential presentations of 22q11 deletion syndromes?

Answer 22

“CATCH-22”

Cleft palate
Abnormal facies
Thymic aplasia --> T-cell deficiency
Cardiac defects
Hypocalcemia 2dary to parathyroid aplasia

d/t microdeletion at chromosome 22q11

Question 23

22q11 deletion syndromes are due to what?

Answer 23

Aberrant development of 3rd & 4th branchial pouches

Question 24

What defects are seen in DiGeorge syndrome?

Answer 24

Thymic, Parathyroid and Cardiac defects

Question 25

What defects are seen in Velocardiofacial syndrome?

Answer 25

Palate, Facial, and Cardiac defects