Chapter 2 Flashcards
The most common chromosomal abnormalities in abortuses are
- 45
- X (Turner syndrome)
- Triploidy
- Trisomy 16
Translocations are particularly common between chromosomes
13,14,15,21 and 22 because they cluster during meiosis
Is caused by an extra copy of chromosome 21 (trisomy 21)
Down syndrome
Features of children with down syndrome include
Growth retardation
Varying degrees of intellectual disability
Craniofacial abnormalities including upward slanting eyes, epicanthal folds, flat faces, small ears
Cardiac defects and hypotonia
High chance of developing leukemia, infections, thyroid dysfunction, and premature aging.
Down syndrome is caused by
Trisomy 31 resulting from meiotic nondisjunction, and in 75 percent of these instances, nondisjunction occurs during oocyte formation.
Kids w Trisomy 18 has the following features
- Intellectual disability
- Congenital heart defects
- Low set ears
- Flexion of fingers and hands
Patients also show micrognathia, renal anomalies, syndactyly, and malformations of the skeletal system.
The incidence of trisomy 18 is
Approximately 1 in 5000 newborns. 85 percent are lost between 10 weeks of gestation and term. Those born alive usually die by 2 months of age. Approx 5 percent live beyond 1 year.
The main abnormalities of trisomy 13 are
- Intellectual disability
- Holoprosencephaly
- Congenital heat defects
- Deafness
- Cleft lip and palate
- Eye defects such as microphthalmia, anophthalmia, and coloboma.
The incidence of trisomy 13 is
1 in 20000 live births and more than 90 percent of the infants die in the first month. Approx 5 percent live beyond 1 year.
Birth defect found only in males and usually detected by amniocentesis
Klinefelter syndrome
Clinical features of Klinefelter syndrome
- Sterility
- Testicular atrophy
- Hyalinization of the seminiferous tubules
- Gynecomastia
The incidence of Klinefelter syndrome is
Approximately 1 in 500 males.
Absence of ovaries
Gonadal dysgenesis
Abnormalities are webbed neck, lymphedema of the extremities, skeletal deformities, and a broad chest with widely spaced nipples.
Turner syndrome
Frequently have problems with speech and self esteem. They have two sex chromatin bodies in their cells.
Triple x syndrome
A well known syndrome cause by partial deletion of the short arm of chromosome 5
Cri-du-chat syndrome
Cri-du-chat affected babies have
- Cat like cry
- Microcephaly (small head)
- Intellectual disability
- Congenital heart disease
Approximately 55% of affected females are monosomic for the X and chromatin body negative because of
Nondisjunction (Turner syndrome) 80% of these females, nondisjunction in the male gamete is the cause
When microdeletion occurs on the long arm of chromosome 15 and microdeletion occurs on the maternal chromosome
Angelman syndrome
Angelman syndrome causes
- Intellectual disability
- Cannot speak
- Exhibit poor motor development
- Prone to unprovoked and prolonged periods of laughter
Microdeletion on the long arm of chromosome 15 occurs in the paternal chromosome
Prader-Willi syndrome
Prader-Willi syndrome
- Hypotonia
- Obesity
- Intellectual disability
- Hypogonadism
- Undescended testes
Characteristics that are differentially expressed depending upon whether the genetic material is inherited from the father or mother are examples of
Genomic imprinting
Regions of chromosomes that demonstrate a propensity to separate or break under certain cell manipulation
Fragile sites
