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61 Cards in this Set

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  • Back
what is the difference between constitutional and acquired chromosome abnormality?
constitutional chromosome abnormality is your chromosome make-up at birth (all tissues) while an acquired chromosome abnormality is an abnormality present only in malignant cells (some tissues only), e.g.
in which cells is chromosome visualization and study limited?
dividing cells (either in vivo or in vitro)
where would one look in vivo to see meiosis? Mitosis?
testis and embryonic ovaries; bone marrow, epithelium, tumors
which cells can be visualized during mitosis in vitro?
lymphocytes, skin, fibroblasts, amniotic fluid cells, chorionic villus cells
to grow up peripheral blood for chromosomal study, T-lymphocytes are stimulated to divide by addition of what? How are these cells blocked in metaphase?
PHA; colchicine
what is the purpose of a hypotonic solution for growing up cells to observe chromosomes in mitosis?
the cells swell which allows for spreading of the chromosomes
which stain is used to visualize chromosomes?
what are the 3 categories of chromosomes based on the location of their centromeres?
metacentric, submetacentric, acrocentric
how are chromosomes prepared for the banding technique?
they are treated with dilute trypsin then stained with Giemsa
what is the name of the technique which allows fluorescent visualization of specific sequences in chromosomes?
FISH (fluorescent in situ hybridization)
how can subtle chromosomal rearrangements involving a certain locus be visualized using FISH?
by using a DNA probe of known chromosomal location
how can microdeletion syndromes be detected in chromosomes?
by using FISH with DNA probes from the region that is commonly deleted in these patients
what is the name given to simultaneous hybridization of a series of DNA probes from a specific human chromosome?
chromosome painting
what is special about FISH using alphoid repeat probes?
the repeats can determine the copy number of a chromosomes in large number of dividing nuclei to identify trisomies or monomies (does not have to be in metaphase)
what is the name for the primary constriction where the sister chromatids of a replicated chromosome are held together until anaphase stage of cell division?
what is the composition of the centromere?
tandem, head-to-tail repeats of a 171-bp monomer that is further organized into higher-order repeats
what is the function of telomeres?
prevent fusion of chromosome ends and maintain chromosome integrity
what is the composition of telomeres? By what are they replicated?
tandem repeats of a simple sequence and an unknown number of proteins; telomerase
what is a metacentric chromosome?
chromosome with arms of approximately equal length, although the short and long arms are defined
what is a submetacentric chromosome?
chromosome with arms of unequal length with clearly identifiable short and long arms
what is an acrocentric chromosome? What is the composition of the p arm?
chromosome with centromere near one end; satellites and stalks which contain redundant copies of ribosomeal RNA genes
in a chromosmes, which arm is p? q?
short; long
what is an ideogram?
a schematic representation of chromosomes with their banding patterns
what does 47,XY,21+ mean in cytogenetic nomenclature?
male with 47 chromosomes (3 on the 21st). This is trisomy 21
what is euploidy?
cells containing a multiple of 23 chromosomes (e.g. triploidy, tetraploidy)
what is aneuploidy?
cells that do not contain a multiple of 23 chromosomes (e.g. trisomy or monosomy)
what is a structural chromosomal abnormality?
rearrangement of chromosomes such as missing a piece or an exchange with another chromosome
what percentage of 1st trimester spontaneous abortions are chromosomally abnormal?
what is the most common genetic cause of moderate mental retardation?
trisomy 21
what is the most common cause of trisomy 21?
non-disjunction most commonly in marternal meiosis I, associated with advanced maternal age
analysis of DNA polymorphisms in patients with numerical chromosomal anomalies allows which information to be determined?
parental origin and cell stage where non-disjunction occurred
Robertsonian translocations occur in which types of chromosomes?
acrocentric chromosomes
what is the phenotype of a patient with a Robertsonian translocation?
what is mosaic trisomy 21?
when non-disjunction takes place in a non-mitotic cell division such that some cells in the body will have a normal karyotype while others will have an extra cheomosome 21
what is another name for trisomy 18? Trisomy 13?
Edwards Syndrome; Patau syndrome
what are the 4 most common trisomies clinically?
which trisomies have the bleakest life expectancy?
13 and 18
in triploidy, how many chromosomes are present in each cell? Where do the extra chromosomes normally come from?
69 chromosomes; the father
what is the major risk of a balanced chromosomal rearrangement (translocation)?
unbalanced gametes and affected children
what is an unbalanced chromosomal rearrangement? Are these individuals usually phenotypically affected?
when rearrangement causes loss or gain of chromosomal material; yes - severly
what are reciprocal translocations?
breakage of nonhomologous chromosomes with reciprocal exchange of chromosome material
what are terminal chromosome deletions?
single breaks leading to loss of chromosome material distal to the breakpoint
what are interstitial chromosome deletions?
where two breaks in chromosome occur and DNA between breaks is lost
what is the phenotype for 'cri du chat' syndrome? Is this most commonly due to a de novo deletion or it is inherited from translocation parents?
terminal deletion of 5p; due mostely to de novo terminal deletion
What is the phenotype of Prader-Willi syndrome (PWS)? Which disease has a very similar phenotype?
interstitial deletion in proximal 15q; Angelmann syndrome (AS)
what is the main difference in the etiology of Prader-Willi and Angelmann syndromes?
PWS is mostly due to microdeletion in paternal 15q whilc AS is mostly due to microdeletion in maternal 15q
why is 15q particularly prone to interstitial deletions?
due to presence of repeated sequences flanking the deleted region and unequal crossing over mediated by these sequences during meiosis
what is the name for 45,X anomaly?
Turner syndrome
what is the name for the inactivation of the only active X chromosome in a cell?
from where is the extra X chromosome derived in 47,XXY?
what is the etiology of 47,XXX?
materal nondisjunction
is 47,XYY a result of maternal nondisjunction? Does it increase with advanced maternal age?
no; no
what is the main reason that 49,XXXXX patients survive?
how many Barr bodies are present in a 49,XXXXX patient?
why do patients with increased or decreased number of X chromosomes have abnormalities despite X-inactivation?
not all genes undergo inactivation and the genes on 'inactivated' chromosomes that remain active lead to altered phenotypes
at which location of the X and Y chromosomes does pairing occur in males during meiosis? What is the name for this region?
distal tips of X and Y chromosomes; pseudoautosomal region
what can occur at the pseudoautosomal region on X and Y chromosomes?
crossing over
which genes of the X chromosomes escape X-inactivation?
genes in the pseudoautosomal region (they are expressed in Y chromosomes)
which factor is responsible for male differentiation in humans?
testis-determining factor (TDF)
how do XX males occur?
crossing over of sex determining gene on Y (SRY) just below pseudoautosomal region to X transfers male characteristics to X chromosome
what is the relationship between cytogenetic changes and malignancy?
many cytogenetic changes are specific to a certain type of malignancy and are used as a routine part of diagnosis