Embryology Flashcards
Spontaneous abortions and chromosomal defects often occur during this week
6-12 weeks
A chromosomal abnormality
Cause: extra copy of chromosome 18
Incidence: 1:5000; Infants usually die by age of 2 months.
SS: Mental retardation, congenital heart defects, low set ears, flexion of fingers
Trisomy 18 or Edwards Syndrome
A chromosomal abnormality
Cause: Three full copies of chromosome 13 in each cell in the body
Incidence: 1:5000; Most of the infants die by age 3 months
SS: Mental retardation, congenital heart defects, low set ears, flexion of fingers
Trisomy 13 or Patau Syndrome
A chromosomal abnormality
Cause: Have 47 chromosomes (XXY) and a 48 (XXXY); the more X chromosomes, more mental impairment
- Nondisjunction of XX homologue
Incidence: 1:5000 in males (detected during puberty)
SS: Sterility or hyalinization of seminiferous tubules
Klinefelter’s Syndrome
A chromosomal abnormality (most common)
Cause: Nondisjunction in male gamete
- Structural abnormality of X chromosomes
- Mitotic disjunction
Incidence: :1:2000 in female births
SS: Low hairline, short stature, shield-shaped thorax, brown spots, no menstruation
Turner’s Syndrome
A chromosomal abnormality
Cause: Random genetic error
- Female have third X chromosome (Nondisjunction or Mosaic)
SS: Girls usually have problems with speech and self-esteem, consist of two sex chromatin bodies in their cells
- often go undiagnosed
Trisomy X or Triple X Syndrome (47, XXX)
A type of structural abnormality
Cause: Partial deletion of chromosome 5
SS: High pitched, cat-like cry, low birth weight, mental retardation, congenital heart disease, microcephaly (small head)
Cri-du chat Syndrome
A type of structural abnormality
Cause: Microdeletion occurs on the long arm of chromosome 15 (15q11-15q13).
- Inherited on maternal chromosome
SS:
→ Mental retardation, cannot speak
→ Poor motor development
→ Prolonged periods of laughter
Angelman’s Syndrome
A type of structural abnormality
Cause:
- Microdeletion occurs on long arm of chromosome 15
- Inherited on paternal chromosome
SS:
- Hypotonia, Obesity, Mental retardation, Hypogonadism, Undescended testes, Cryptorchidism
Prader-Willi Syndrome
A type of structural abnormality
Cause:
- a break or weakness on the long arm of X chromosome
Incidence:
- 1:5000, individuals with males affected more than females
- 2nd most common inherited cause of mental retardation due
to chromosomal abnormalities
SS:
- Mental retardation, large ears, prominent haw, pale blue
irises
Fragile X Syndrome
A type of structural abnormality
Cause:
- Contiguous gene syndrome inherited from parent
SS:
- Developmental delay, Seizures
- Cardiac and facial abnormalities (deletion at 17p13)
- Palatal defects, conotruncal heart defects, speech delay, learning disorder, and schizophrenia (deletion at 22q11).
Miller-Dieker Syndrome