医学遗传学染色体2

XXY, Klinefelter’s syndrome
X-green, Y-red
47, XXY
47, XYY syndrome
1:1,000 in male live birth Normal intelligence and normal appearance
but: 1. Educational problem: language delays and
Trisomy 18 Edward’s syndrome
18-green, X-aqua
47, XY, +18 NhomakorabeaTrisomy 13 Patau’s syndrome
1:20,000 in liveborn and more common in abortion and stillbirth
Serious structural anomalies lead to death in one month
(3) Mosaic and chimera
Aberration Aberration
Mosaic Chimera
Mosaic and chimera
45,X/47,XXX
Chromosomal disorders or diseases With phenotypic alteration
The process is controlled by XIST (X inactive specific transcripts) gene in Xq13.2, which encodes a large RNA that appears to "coat" the X chromosome and facilitate inactivation of genes on the X chromosome.
47, XYY syndrome
47, XYY
47, XXX syndrome
1:1,000 in Female live birth Normal intelligence and normal
appearance A significant deficit in performance on IQ
tests 70 % with some learning problems Infertility: 50%
47, XXX syndrome
47, XXX
XXXXX Syndrome
Why?
Autosome: only trisomy 21, 18 and 13 found in livebirth, no monsomy
Barr body
During the late blastocyst stage, all X chromosomes except one undergo heterochromatinization and form X chromatin bodies in each cell.
The balance of gene dosage on X chromosome is achieved. The explanation of various kinds of X polysomies in live-birth.
spelling difficulties 2. Behavioral problems: attention deficits,
hyperactivity and impulsiveness 3. Fertility problem: increase risk of chromosomal
abnormal child
49, XXXXX
Sex chromosome in livebirth: XO, XXX, XXY, XYY, XXXX, XXXXX
X chromosome inactivation and XIST
Gene dosage compensation is achieved in all persons with two or more X chromosomes in their genetic constitution by partial inactivation of all X chromosomes except one.
protruding tongue Short and broad hand with
a single transverse palmar crease
Trisomy 21 Down’s syndrome
Related with advanced maternal age
Age of Women 20-29 30-34 35-40 40-45
Trisomy 13 Patau’s syndrome
13-green, 21-orange
47, XY, +13
XXY, Klinefelter’s syndrome
1:1,000 in male liveborn
Hypogonadism and Infertility:
1. Tall stature 2. Long limbs 3. Small genitalia 4. Gynecomastia
Birth Rate 1;1500 1:1000 1:100 1:40
Trisomy 18 Edward’s syndrome
1:7500 in liveborn and more common in abortion and stillbirth
Sever mental retardation and multiple structural anomalies
Trisomy 21 Down’s syndrome
Most common trisomy 1:800 in new born
Most common serious mental retardation
Trisomy 21 Down’s syndrome
Eyes with brushfield spot Flat nosal bridge Low set ear Open mouth with