Lecture 26 Flashcards Preview

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Flashcards in Lecture 26 Deck (16):
1

what is the cause of a miscarriage 50% of the time?

chromosomal abnormalities

2

when should you order a chromosome test?

- prenatal findings: fetus has a growth retardation, multiple congenital anomilies, or edema in the ultrasound.
- Infancy and childhood: multiple congenital anomalies, unusual facial features, short stature, mental retardation, learning or attentional difficulties
- adulthood: learning disabilities, infertility, history of recurrent pregnancy loss or stillbirths

3

what is the acronym used to aid physicians in looking for clues that may indicate chromosomal anomalies?

FBGD (funny bodies got disorders)

F: unusual Facial features from the parents
B: birth defects or variations in physical features
G: growth retardation (ie. microcephaly)
D: developmental problems (mental retardation, learning disabilities, attention disorders.

4

what are some features of Trisomy 21.

- down syndrome
- mostly due to nondisjuntion with chromosome 21, rarely ever a robertsonian translocation though (4%)
- seen in moms that are younger usually

5

what occurs in Trisomy 21 monosaicism?

- very rare (1-2%)
- some cells lost the extra 21 chromosome while other retained the trisomy so milder symptoms.

6

what is the FBGD for trisomy 21?

F - distinct eyes, face, and neck
B - a third have a heart defect (pig duct arteriosis doesn't close between the pulmonary artery and descending aorta). Some have intestinal defects.
D - differing degrees of mental retardation and premature growth.

7

what are some of the features of Trisomy 18?

- much more severe than Trisomy 21
- much more rare (1/7,500 vs 1/800 for DS)

8

what is the FBGD for trisomy 18?

F - microcephaly among many others
B - serious heart defects, kidney malformations, intestinal malformations
G - severe mental retardation. 95% don't survive past first year of life.

9

What are some features of trisomy 13?

- more rare than trisomy 18 (1/15,000 vs 1/7,500)
- involves chromosome which is an acrocentric chromosome so it is possible to get a robertsonian translocation.

10

what are the more common chromosome abnormalities that are alleviated due to mosaicism?

- Sex chromosome abnormaliites
- trisomy 21 and 16

11

what is the most common microdeletion and what does it result in?

- the 22q deletion that results in DiGeorge or velocardiofacial syndrome.

12

what is the most common chromosomal abnormality at the moment of conception?

turner syndrome and only 1% of them go on to be born.
- only one X chromosome mostly due to an egg being fertilized by a sperm that is missing an X or Y chromosome.

13

what are the features of turner syndrome?

short stature, ovarian failure, late onset of puberty.
- visual spatial perceptual problems.

14

what are the features of triple X?

- no physical features are apparent
- mild learning difficulties with slight psychiatric and behavioral problems
- women have early menopause, premature ovarian failure but otherwise normal fertility

15

what are the features of klinefelter syndrome?

(47, XXY)
- no physical deformations at birth
- small testes, adolescent breast development (increased risk of breast cancer).
- infertile.

16

what occurs at the 14th cell stage and who discovered this?

Lyon discovered that at the 14th cell stage each cell shuts own one of its C chromosomes randomly and permanently. Each subsequent daughter cell will have the same X inactivation present.