Chromosomal and Genomic Basis of Disease Flashcards
what disease is the most common genetic cause of moderate intellectual disability
down syndrome
how many cases of down syndrome are there
1/850
what are the signs/symptoms of down syndrome
hypotonia, dysmorphic facial features, short in hands, neck, hands, and simian crease
what accounts for <95% of DS
47 chromosome due to meiotic nondisjunction of chromosome 21 pair
nondisjunction during maternal ________ is common meiotic error resulting in DS
meiosis I
what does nondisjunction event lead to
leads to production of abnormal gamete with two copies or no copies of chromosome in meiosis I
what does trisomy result from
results from meiotic nondisjunction of chromosome 21 pair
what is contiguous gene syndrome
extra or deficient copies of multiple contiguous genes within deleted or duplicated region due to genomic regions predispose to rearrangements
what causes Turner’s syndrome
missing an X chromosome on 23rd pair
what is klinefelter syndrome
males who have 47 chromosomes with 2 x chromosomes and y chromosome
how many chromosomes do women with turners syndrome have
45 chromosomes with 1 x chromosome
what are signs/symptoms of children with prader willi syndrome
obestity, hypogonadism, small hands & feet, short stature and development delay
signs/symptoms of children with Angelman syndrome
wide stance and position of arms
what roles does Y chromosome have
role in sex development
the X and Y chromosome pair by segments at
ends of their short arms
Y chromosome undergoes…
recombination with a specific region of the X chromosome
X chromosome contains most common
cytogenetic abnormalities
what disorders are caused by micro-deletion and duplication
development delay, intellectual disability, and dysmorphic features
what is mechanism for microdeletion/duplication or continguous gene syndrome
breakpoints located at low-copy repeated sequences (segmental duplications) in genome
what are genomic disorders from del/dup in 22q11
intellectual disability, heart defects, absent pulmonary valve
what is x chromosome inactivation
one of the two x chromosomes are silenced epigenically (x linked disorders)
example of x chromosome disorder
klinefelter syndrom : 1/600, increase risk of breast cancer, and decreased muscle tone and bone density
what percentage of genomic imbalance are caused by multiple rare copy number variants
12-16%
