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111 Cards in this Set

  • Front
  • Back
The study of chromosomes and their abnormalities
cytogenetics
Leading cause of mental retardation and pregnancy loss
Chromosome abnormalities. 1 in 150. 50% first trimester and 20% second trimester spontaneous abortions
Function of colchicine and colcemdi
spindle poisons that arrest dividing somatic cells in metaphase when chromosomes maximally condensed and easiest to see
karyotype
number and type of chromosomes present in an individual
karyogram
printed display of chromosomes
metacentric chromosome
If a centromere occurs near the middle of the chromosome
acrocentric chromosome
centromere near the tip
submetacentric chromosomes
Centromeres somewhere between the middle and the tip
Telomere
tip of each chromosome
p arm
the short arm of a chromosome
q arm
the long arm of the chromosome
46,XY
normal male chromosome karyotype
47,xx,+21
female trisomy 21 karyotype
47,xy,+21[10]/46,xy[10]
Male who is a mosaic of trisomy 21 cells and normal cells (10 cells scored for each karyotype)
46,xy,del(4)(p14)
male with distal and terminal deletion of the short arm of chromsome 4 from band p14 to terminus karyotype
46,xx,dup(5)(p14p15.3)
Female with duplication within short arm of chromosome 5 from bands p14 to p15.3 karyotype
45,xy,der(13;14)(q10;a10)
male with balanced robertsonian translocation of chromosomes 13 and 14. Karyotype shows one normal 13 and one normal 14 are missing and replaced with derivative chromosome composed of the long arms of chromosomes 13 and 14
46,xy,t(11;22)(q23;q22)
male with balanced reciprocal translocation between chromosomes 11 and 22. The breakpoints are at 11q23 and 22q22
46,xx,inv(3)(p21q13)
An inversion on chromosome 3 that extends form p21 to q13. Includes th centromere so it is a pericentric inversion
46,x,r(x)(p22.3q28)
Female with one normal x chromosome and one ring x chromosome formed by breakage at bands p22.3 and q28 with subsequent fusion
46,x,i(Xq)
A female with one normal x chromosome and an isochromosome of the long arm of the x chromosome
R-banding
for staining the distal ends of chromosomes
C-banding
for staining the constitutive heterochromatin near the centromere
NOR staining
highlights the satellites and stalks of acrocentric chromosomes
High-resolution banding
staining that binds during prophase and early metaphase. allows detection of less obvious abnormalities
FISH
single stranded DNa segment exposed to denatured metaphase, prophase, or interphase chromosomes. Probe then undergoes complementary base pairing (hybridization) with complementary DNA
use of FISH
Whether a portion of a chromosome is deleted is detected with this method. Deletions detected as small as 1 Mb
Fish probes
These probes can be used to detect chromosome rearrangements such as translocations
Smith-Magenis with broad forehead and flat face
Deletion in 17p diagnosis and symptoms
FISH analysis of interphase
Technique used in prenatal detection of fetal chromosome abnormalities and analysis of chromosome rearrangements in tumor cells
Spectral karyotyping
Combination of five different fluorescent probes to identify small chromosome rearrangements
Comparative genomic hybridization (CGH)
technique for detection of losses or duplications of whole chromosomes or specific regions. Cant detect translocations or inversions
Euploid
multiple of 23
Polyploidy
presence of a complete set of extra chromosomes
Triploidy
69 chromosomes and causes 15% of chromosome abnormalities at conception caused by fertilization of an egg by two sperm (dispermy)
Meiotic failure
When a diploid sperm or egg cell is produced
Tetraploidy
A mitotic failure of the early embryo with 92 chromosomes
Aneuploid
Missing or additional individual chromosomes
Monosomy
presence of only one copy of a chromosome
Body tolerates excess genetic material more readily than a deficit
Body tolerates excess genetic material more readily than a deficit
Nondisjunction
the most common cause of aneuploidy
Nondisjunciton
failure of chromosomes to disjoin normally during meiosis
Down syndrome
Low nasal root, upslanting palpebral fissures, small and overfolded ears, flattened maxillary and malar region. Mongolism. Round cheeks, corners of mouth downturned, short neck, feet are short and broad, deep flexion crease across palms called simian crease, decreased muscle tone. Leukemia is 15-20 times higher and many have heart defects
Meiosis I for 75%
Most of maternal nondisjunctions occur during which meiosis
Trisomic conception folllowed by loss of extra chromosome during mitosis
Mosaicism for down syndrome
AV canals
Most common heart defect in newborns with Down syndrome
DYRK1A
Gene for mental retardation in Down syndrome
APP
Responsible for occurrence of Alzheimer disease in Down
47,xy,+18
Trisomy 18 (Edwards Syndrome)
Trisomy 18
Hand abnormality, prenatal growth deficiency, small ears with unraveled helices, small mouth, short sternum, short halluces
VSD
Most common heart defect in trisomy 18
Trisomy 18
omphalocele, radial aplasia, diaphragmatic hernia, and sometimes spinal bifida
High mortality causes of trisomy 18 patients
aspiration pneumonia, presidposition to infections, and congenital heart defects
Trisomy 13
Patau syndrome
Trisomy 13
oral-facial clefts, microphthalmia, postaxial polydactyly, malformation cns, heart defects, renal abnormalities, cutis aplasia
Trisomy 13 and 18 mortality rate
mortality rate of 95% for these two
Monosomy of x chromosome
Turner Syndrome
Turner syndrome
short stature, sexual infantilism, ovarian dysgenesis, triange shaped face, webbed neck, lymphedema of the hands and feet
Obstructive lesions of the left side of the heart (bicuspid aortic valve)
Most common heart defect in turner syndrome
Turner syndrome has this mosaicism
Confined placental mosaicism is found where?
Paternal sex chromosome
Chromosome that is culprit in turner syndrome
SHOX gene
Gene for short stature in turner syndrome
SRY acts on DAX1 to stop it from repressing male genes
What stops DAX1
Klinefelter syndrome karyotype
47,xxy
Klinefelter syndrome affect
cause of primary hypogonadism in males
Klinefelter syndrome symptoms
Tall, disproportionate long arms and legs, small testes, gynecomastia
Klinefelter syndrome
Testosterone therapy
Trisomy X
47,xxx karyotype
Trisomy x signs
sterility, menstrual irregularity, mild mental retardation
Trisomy x cause
90% are nondisjunction in mother
47,xyy signs
low IQ, minor behavioral disorders
One third of pregnancies lost after implantation
How many pregnancies lost after implantation
Balanced structural abnormalities do not produce serious health consequences
Balanced structural abnormalities do not produce serious health consequences
Clastogens such as ionizing radiation, viral infections, some chemicals
harmful agents that increase chance of chromosome breakage
Translocation
interchange of genetic material between nonhomologus chromosomes
Reciprocal and Robertosnian
The two types of translocations
Reciprocal tranlocation
Breaks in two different chromosomes and material is mutually exchanged resulting in a derivative chromosome. Can result in partial trisomy for offspring
Robertsonian translocation
short arms of two nonhomologus chromosomes lost and long arms fuse to form one chromosome
Robertsonian is in the acrocentric region
Region of Robertsonian translocation
Adjacent segregation
Type of segregation in Robertsonian that leads to Downs
Termial deletion
Single break leading to loss that includes chromosome tip
Interstitial deletion
Two breaks occur and material between breaks is lost
cri-du-chat syndrome
Deletion of distal short arm of chromosome 5 (46,xy,del(5p))
Cri-du-chat
IQ of 35, microcephaly
Wolf-Hirschhorn syndrome
deletion of short arm of chromosome 4
Prader willi syndrome
A microdeletion syndrome in bands 15q11-q13
Williams syndrome
mental retardation, supravalvular aortic stenosis (SVAS), multiple peripheral pulmonary arterial stenoses,hypercalcemia is a microdeletion
Deletions of elastin
Deletions of what result in SVAS
LIMK1
deletion of gene in williams syndrome that is involved in visual-spatial cognition
WAGR syndrome
deletion of 11p including wilms tumor, aniridia (absence of iris) genitourinary abnormalities, and mental retardation
DiGeorge sequence
defects of thymus, conotruncal heart defects, hypoparathyroidism, secondary hypocalcemia
DiGeorge Syndrome deletion
deletion of 22q
VCF or velocardiofacial syndrome, or shprintzen syndrome
palatal abnormalities and heart malformations with learning disabilites. Same deletion on 22q
TBX1
gene that encodes transcription factor to regulate migration of neural crest cells
monosomy 1p36
mental retardation, developmental delay, seizures, hearing impairment, heart defects, hypotonia, horizontal eyebrows, deep-set eyes, broad nasal root
subtelomeric rearrangements
dleetion or duplicatoin of dna in gnee rich regions near telomeres
uniparental disomy
one parent contributes two copies of a chromosome. Seen in Prader willi when cause is not a microdeletion
isodisomy
parent that contributes two copies of one homolog
heterodisomy
ony copy of each homolog
cystic fibrosis
uniparental disomy causes this
Duplication
Seen in offspring of people who carry reciprocal translocaiton, such as Charcot-marie-tooth disease
Pericentric inversion
inversion with centromere
paracentric inversion
inversion without centromere
recombinant 8 syndrome
mental retardation, heart defects, seizures with inversion on chromosome 8 when offspring get deletion or duplication of long arm
isochromosome
Chromosome with two copies of one arm and no copies of another because it divides along axis perpendicular to usual axis
Turner syndrome is like this
isochrome x has features of turners
Edwards syndrome is like this
isochrome 18q has features like this
Philadelphia chromosome
translocation between chromosomes 9 and 22 where most of 22 goes onto long arm of 9
ABL leads to malignancy in hematopoietic cells in this
philly chromosome alters ABL gene which leads to what
Burkitt lymphoma
jaw tumor for reciprocal translocation between 8 and 14 which moves MYC proto-oncogene
Chromosome instability syndroms
increased chromosome breaks under lab conditions that include ataxis-telangiectasia, bloom syndrome, fanconi anemia, xeroderma pigmentosum