What causes Down syndrome?
Trisomy 21 resulting in extra chromosome 21.
Key features of Down syndrome?
Intellectual disability, flat facial profile, simian crease, AV septal defect, increased maternal age risk.
What causes Edwards syndrome?
Trisomy 18 due to extra chromosome 18.
Key features of Edwards syndrome?
Micrognathia, clenched fists, rocker-bottom feet, congenital heart defects.
What causes Patau syndrome?
Trisomy 13 due to extra chromosome 13.
Key features of Patau syndrome?
Holoprosencephaly, cleft lip/palate, polydactyly, cardiac defects.
What is Turner syndrome?
Monosomy X (45,X).
Key features of Turner syndrome?
Short stature, webbed neck, streak ovaries, coarctation of aorta, lymphedema.
What is Klinefelter syndrome?
47,XXY in males.
Key features of Klinefelter syndrome?
Tall, hypogonadism, infertility, gynecomastia, mild learning difficulty.
What is Triple X syndrome?
Presence of an extra X chromosome in females (47,XXX).
Key features of Triple X syndrome?
Often normal phenotype, possible mild learning disability.
What causes Cri-du-chat syndrome?
Deletion of short arm of chromosome 5.
Key features of Cri-du-chat syndrome?
Cat-like cry, microcephaly, mental retardation.
What causes DiGeorge syndrome?
22q11 microdeletion affecting neural crest derivatives.
Key features of DiGeorge syndrome?
Thymic hypoplasia, hypocalcemia, cardiac defects.
What causes Prader–Willi syndrome?
Loss of paternally expressed genes on chromosome 15.
Key features of Prader–Willi syndrome?
Obesity, hypotonia, hyperphagia.
What causes Angelman syndrome?
Loss of maternal genes on chromosome 15.
Key features of Angelman syndrome?
Severe developmental delay, seizures, ataxia, inappropriate laughter.
Cause of Achondroplasia?
FGFR3 mutation causing inhibited cartilage proliferation.
Cause of Marfan syndrome?
FBN1 mutation affecting fibrillin-1.
Cause of cystic fibrosis?
CFTR gene mutation causing thick secretions.
Cause of PKU?
PAH gene mutation causing phenylalanine buildup.
