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Flashcards in Biochem15 Deck (25):
1

Down syndrome is trisomy ___.

21 (1:700)

Down's - Drinking age - 21

2

What are some characteristic findings in trisomy 21?

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

3

95% if trisomy cases are due to what?

Meiotic nondisjunction of homologous chromosomes

4

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

1:1500 45

5

4% of trisomy 21 cases are due to what?

Robertsonian translocation

6

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

DECREASED: alpha-fetoprotein & estriol

INCREASED: beta-hCG & inhibin A

7

What does ultrasound show in trisomy 21 cases?

INcreased nuchal in first trimester translcency

8

Edwards' syndrome is trisomy ___.

18 (1:8000)

Edwards - Election age - 18

9

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

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

10

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

DECREASED:
- alpha-fetoprotein
- beta-hCG
- estriol

NORMAL: inhibin A

11

Patau's syndrome is trisomy __.

13 (1:15,000)

"Patau - Puberty - 13"

12

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

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

Death usually occurs within 1 year of birth

13

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

DECREASED:
- beta-hCG
- PAPP-A

INCREASED:
- nuchal translucency

14

What is Robertsonian translocation?

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

One of the most common types of translocations

15

When do Robertsonian translocations occur?

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

16

What are an acrocentric chromosomes?

chromosomes with centromeres near their ends

17

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

Unbalanced

Balanced normally do not cause any abnormal phenotypes

18

What causes Cri-du-chat syndrome?

Congenital microdeletion of short arm of chromosome 5

(46,XX or XY, 5p-)

19

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

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

"Cri du chat = cry of the cat"

20

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

Williams syndrome

elastin gene

21

What are the findings in WIlliams syndrome?

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

22

What are the potential presentations of 22q11 deletion syndromes?

"CATCH-22"

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

d/t microdeletion at chromosome 22q11

23

22q11 deletion syndromes are due to what?

Aberrant development of 3rd & 4th branchial pouches

24

What defects are seen in DiGeorge syndrome?

Thymic, Parathyroid and Cardiac defects

25

What defects are seen in Velocardiofacial syndrome?

Palate, Facial, and Cardiac defects