Chromosomal Disorders

• What is aneuploidy?

  Chromosome number not a multiple of haploid set
• What happens when one chromosome is lost from a diploid cell?

  It produces a diploid number minus one (2n – 1)
• What is haploinsufficiency?

  A lethal condition due to insufficient gene function
• What does aneuploidy during gamete formation produce?

  Equal numbers of monosomic and trisomic gametes
• What is the diploid number when one chromosome is added?

  It produces a diploid number plus one (2n + 1)
• What percentage of chromosomal abnormalities causing fetal death are autosomal trisomies?

  50%
• What is Trisomy 21 also known as?

  Down syndrome
• Who discovered Down syndrome and when?

  Langdon Down in 1866
• What is the prevalence of Down syndrome?

  1 in 700 births
• What is the leading cause of mental retardation in the US?

  Down syndrome
• What are some physical features of Down syndrome?

  Wide flat skulls and thick, furrowed tongues
• What percentage of individuals with Down syndrome may have congenital heart defects?

  40%
• What is translocation Down syndrome?

  Involves chromosome 14 with Robertsonian translocation
• What is the frequency of Down syndrome at age 30?

  1 in 1000
• What is the frequency of Down syndrome at age 40?

  1 in 100
• What is the frequency of Down syndrome at age 45?

  1 in 30
• What is Trisomy 18 also known as?

  Edwards syndrome
• What is the average survival time for infants with Edwards syndrome?

  2–4 months
• What are common characteristics of infants with Edwards syndrome?

  Small at birth and grow slowly
• What is Trisomy 13 also known as?

  Patau syndrome
• What is Turner’s Syndrome karyotype?

  45, X
• What is the mean survival time for infants with Patau syndrome?

  1 month
• What is Klinefelter Syndrome karyotype?

  47, XXY
• What are some features of Patau syndrome?

  Facial malformations and extra fingers or toes
• What are common features of Turner’s Syndrome?

  Short stature and rudimentary ovaries
• What is the prevalence of Turner’s Syndrome?

  1 in 10,000 births
• What are features of Klinefelter Syndrome?

  Males with low fertility and tall stature
• What is the prevalence of Klinefelter Syndrome?

  1 in 1000 births
• What is Jacob Syndrome karyotype?

  47, XYY
• What did Patricia Jacobs study in 1965?

  Jacob Syndrome in Scottish prisoners
• What is the prevalence of Jacob Syndrome?

  1 in 1000 births
• What are some physical symptoms of Jacob Syndrome?

  Taller than average height and low muscle tone
• What is Trisomy X also known as?

  Triplo X
• What is the prevalence of Trisomy X?

  1 in 1000 births
• What are some symptoms of Trisomy X?

  Delayed speech and learning disabilities
• How does maternal age affect aneuploidy risk?

  Risk increases due to meiotic nondisjunction errors
• What is Cri du chat syndrome caused by?

  Chromosome deletion on chromosome 5
• What does the name Cri du chat mean?

  Cat-cry or cry of the cat
• What is Prader-Willi syndrome caused by?

  Deletion of the long arm of chromosome 15