NYU SCHOOL OF MEDICINE

CYTOGENETICS LECTURE 2

Mary Ann Perle, Ph.D.

TRANSLOCATION

46,XX,t(4;10)(p14;q11.2)

FEMALE WITH A RECIPROCAL TRANSLOCATION BETWEEN THE SHORT ARMS OF A #4 AND LONG

ARMS OF A #10

46,XY,der(10)t(4;10)(p14;q11.2)mat

ABNORMAL MALE: UNBALANCED KARYOTYPE WITH AN ABERRANT #10 DERIVED FROM A MATERNAL 4q;10q

TRANSLOCATION

Fre

qu

ency

/ 10

00 B

irth

s

Frequency of Down syndrome at birth related to maternal age.

Maternal Age

TEST

TEST

35 y.o.

40 y.o.

Simian crease

Fig. 2.27a-c. Children with Down syndrome. a. European, b. Afro-American, c. Asian. The common features of Down syndrome are more impressive than the racial differences. Courtesy of Dr. T.M. Schroeder-Kurth

47,XX,+18

ABNORMAL FEMALE WITH TRISOMY 18

Fig. 3-6. Two infants illustrating craniofacial characteristics of trisomy 18 (prominent occiput, low-set malformed ears and small chin).

47,XX,+13

ABNORMAL FEMALE WITH TRISOMY 13

69,XXX

ABNORMAL FEMALE WITH CHROMOSOMAL

TRIPLOIDY

Fluorescence In Situ Hybridization

A molecular tool used to detect genetic abnormalities

A DNA probe finds target sequences on chromosomal DNA as they are found in cells – “in the original place”

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PARTIAL

Normal X Ring “Dot”

Chromosome 2 = Red

X chromosome = Green

Angelman Syndrome (deletion 15q11-q13)

q11q13

Angelman Syndrome: 15q11probe

FISH for IgH/14q32 (dual color breakapart probe)

Two fusion signals indicating no rearrangement of IgH locus

NORMAL BONE MARROW

FISH for IgH/14q32 Split signal indicating positive rearrangement

of IgH locus

ABNORMAL BONE MARROW