Term
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Definition
| Centromere near central region of chromosome |
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Term
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Definition
| Centromere is off-center, arms of clearly different lengths |
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Term
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Definition
Centromere near one end (chromosomes 13,14,15, 21, and 22)
Contain small, distinctive masses of chromatin satellites
Attached to p arms by narrow stalks
Contain hundreds of copies of ribosomal RNA genes |
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Term
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Definition
| Centromere at one end and only has a single arm (does not occur in a normal human Karyotype) |
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Term
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Definition
Most common method
Chromosomes from prometaphase or metaphase cells
Treated with trypsin to digest proteins
Produces characteristic light and dark bands (400 bands) |
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Term
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Definition
Staining with quinacrine mustard or related compounds
Examination by fluorescence microscopy
Bright Q bands correspond exactly to dark G bands
Useful for detecting heteromorphisms (variants in chromosome morphology)
Generally benign and reflect differences in satellite DNA amounts |
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Term
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Definition
Chromosomes receive special treatment such as heating before staining
The Dark and Light band pattern is the inverse of that observed by G or Q banding
Useful for examining regions that stain poorly by G or Q banding, somewhat easier to analyze
Frequently used method in Europe |
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Term
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Definition
Identifies a subset of the R-bands which are especially concentrated at the telomeres
Visualized by:
Severe heat treatment before staining with Giemsa
Use of a combination of dyes and fluorochromes |
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Term
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Definition
Staining centromeric regions of each chromosome and other regions containing constitutive heterochromatin
1q, 9q, 16 q adjacent to Centromere and distal part of Yq |
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Term
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Definition
| condensed chromatin, typically transcriptionally inactive. Stains darkly in non-dividing cells |
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Term
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Definition
Prometaphase banding
G- or R- banding of chromosomes from a prophase or prometaphase cell
Chromatin is less condensed
Useful for detecting subtle structural abnormalities in a chromosome
Can reveal 550 to 850 bands or more in a haploid set |
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Term
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Definition
Non-staining gaps in metaphase chromosomes
Occasionally observed at characteristic sites on several chromosomes |
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Term
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Definition
Name the disease. Detection of fragile site diagnostic procedure specific for X chromosome
Mostly replaced by molecular testing for CGG triplet repeat expansion
FMR-1 gene |
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Term
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Definition
Examines and evaluates
Presence or absence of a particular DNA sequence
Number or organization of a chromosome or chromosomal region
Uses probes
Highly specific single locus
Chromosomal “painting” entire chromosome
Multiple different fluorochromes
Spectral karyotyping |
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Term
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Definition
DNA analysis on genomic level
Uses comparative genome hybridization (CGH)
Contain
Complete representation of entire genome OR
Series of cloned fragments spaced at various intervals |
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Term
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Definition
Complements karyotyping
More sensitive and high resolution assessment
Does only detects loss or gain of genetic material
Not mechanism |
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Term
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Definition
Translocation
Rearrangements from normal position
Needs to be verified by ____ |
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Term
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Definition
Phenotype in ___ ____depends on
Size of unbalanced segment
Whether imbalance is monosomic or trisomic
Genes and regions affected and involved |
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Term
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Definition
Commonly mosaic
Phenotype specific to genomic region involved
what type of chromosome is this describing? |
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Term
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Definition
in this type of inversion the risk of birth defects increases with size of inversions; involving centromere
Produce unbalanced gametes with duplication and deficiency of segments distal to inversion |
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Term
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Definition
in this type of inversion there is a very low risk of abnormal phenotype;not involving centromere
Leads to unbalanced gametes with acentric or dicentric recombinant chromosomes which are not viable |
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Term
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Definition
| an unbalanced translocation between 3p and 11q was not evident using G banding but can be revealed by using what method? |
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Term
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Definition
| Red signal on proximal 15q is a probe for what gene? |
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Term
| Meiotic Nondysjunction in oogenesis |
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Definition
most common mutational mechanism responsible for chromosomally abnormal fetuses
leading cause of developmental defects
Failure to thrive
Mental retardation in newborns |
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Term
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Definition
Chromosomal mosaicism
Tumors
Important diagnostic and prognostic test in cancers |
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Term
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Definition
| this type of mutation is Less frequent compared to genome mutations (6 x 10-4/cell divisions = 1 rearrangement per 1700 cell divisions) |
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Term
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Definition
chromosome number that is a multiple of n(=23)
Diploid (2n) is 46 chromosomes –characteristic of normal somatic cells |
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Term
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Definition
| Any chromosome complement other than 46 |
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Term
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Definition
Frequently results from fertilization by two sperm
Arise from failure of one of the meiotic divisions
Partial hydatidiform moles |
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Term
| abnormal placenta; spontaneous abortion |
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Definition
| if you have extra paternal chromosomes what usually happens? maternal? |
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Term
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Definition
| Results from failure of completion of an early cleavage division of the zygote |
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Term
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Definition
| number of chromosomes that is not a multiple of the haploid number; result of meiotic nondisjunction |
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Term
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Definition
| Failure of a pair of chromosomes to separate properly in meiosis I (common) or meiosis II |
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Term
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Definition
gamete with 24 chromosomes
Both maternal and paternal members of pair is a consequence of nondisjunction when? |
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Term
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Definition
gamete with 24 chromosomes
Either maternal or paternal copies of the pair is a consequence of nondisjuction when? |
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Term
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Definition
| nondisjuction in mitosis leads to? |
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Term
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Definition
Pass unaltered through mitotic and meiotic divisions
Requires normal structural elements
Functional centromere and
Two telomeres |
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Term
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Definition
| Mental retardation May be diagnosed by targeted cytogenetic analysis of telomeric regions by ____ |
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Term
| unexplained mental retardation |
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Definition
| Terminal deletion of chromosome 1p results in pateint with |
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Term
| Pallister-Killian syndrome |
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Definition
Partial duplication of chromosome 12p
Normal karyotype with symptoms of ? |
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Term
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Definition
| De novo deletion (5 Mb) of chromosome 7q22 results in a patient with an _____ _____ |
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Term
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Definition
Loss of a chromosomal segment
Caused by
Chromosomal breakage and loss of acentric segment
Unequal crossing over
Abnormal segregation of a balanced translocation or inversion
May be terminal or interstitial
Results in partial monosomy
May result in haploinsufficiency and phenotype
Detected by high resolution banding and FISH is what type of rearrangment |
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Term
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Definition
Subclass of marker chromosomes
Small fragments of chromosomes that do not have centromeric sequences;
Mitotically stable
Must have somehow acquired centromers activity |
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Term
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Definition
Marker chromosomes without Telomeres
Formed by loss of terminal ends of both arms and the ends join together
Rare; mitotically unstable |
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Term
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Definition
Chromosome in which one arm is missing and the other duplicated in a mirror image fashion
Mechanism
Misdivision through centromere in meiosis II
Exchange involving one arm of a chromosome and its homolog at the proximal edge of the arm adjacent to centromere |
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Term
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Definition
| what is the Most commonly observed: isochromosome? |
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Term
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Definition
Rare
Two chromosome segments, each with a centromere fused end to end |
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Term
| pseudiocentric chromosome |
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Definition
| can be mitotically stable if the two centromeres are coordinated in their movement during anaphase or one centromere is inactivated |
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Term
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Definition
what type of rearrangement?; Normally no phenotypic effect in carrier individuals
Likely to produce unbalanced gametes increased risk of abnormal offspring
May disrupt a gene mutation |
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Term
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Definition
Lethal disorder with severe cardiac abnormalities and mental retardation
Primarily found in Hispanics from SW USA |
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Term
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Definition
| Most common is _______ –no known deleterious effects considered a normal variant |
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Term
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Definition
Reported in North America
Families with ancestors in maritime provinces of Canada
Carriers of inversion are normal
40% of carriers have abnormal offspring
Recombinant chromosome 3
Duplication of segment distal to 3q21 and deletion of segment distal to 3p25 |
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Term
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Definition
Break in two different chromosomes and the material exchanged
Relatively common
Associated with unbalanced gametes and abnormal progeny |
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Term
| robertsonian translocation |
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Definition
Long arms (q arm) of two non-homologous acrocentric chromosomes fuse at the centromere forming a single chromosome and the short arm (p arm) is lost
Balanced karyotype with 45 chromosomes
Short arms of all 5 pairs of acrocentric chromosomes have multiple copies of rRNA genes deletions not deleterious
13q14q 1 in 1300 incidence most common chromosome rearrangement |
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Term
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Definition
Nonreciprocal type of translocation
A segment removed from one chromosome is inserted into a different chromosome
Require 3 breaks relatively rare
High risk of abnormal offspring up to 50% |
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Term
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Definition
| mosaicism that arises in cell culture |
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Term
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Definition
| Most common observed (20%)is abortuses is |
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Term
| beckwith weidemann, prader willi, angelman |
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Definition
| give 3 examples of uniparetal disomy |
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Term
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Definition
Caused by abnormal growth of chorionic villi epithelium proliferates and stroma undergoes cystic cavitation
Placenta is converted into a mass of tissues resembling “a bunch of grapes”.
Occurs when a sperm fertilizes an ovum that lacks a nucleus duplication of haploid male chromosome set (sperm chromosomes)
Can lead to choriocarcinoma |
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Term
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Definition
Benign tumors, arise from 46, XX cells containing only maternal chromosomes
Reciprocal to complete moles |
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Term
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Definition
Triploid
In most cases extra set of chromosomes paternal
Abundant trophoblast and poor embryonic development
Extra maternal material severe retardation of embryonic growth with small and fibrotic placenta |
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Term
| Confined Placental Mosaicism |
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Definition
Placenta has mosaic for an abnormality, that is not apparent in the fetus
But leads to abnormal fetus |
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Term
| DNA polymorphism or cytogenetic heteromorphism analysis |
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Definition
Large study: >1000 aneuploid fetuses
Significantly different contribution of maternal and paternal nondisjunction
Maternal
>90% of all Down Syndrome cases
100% of trisomy 16
50% of Klinefelter
20 – 30% of all Turner cases |
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Term
| Direct analysis of chromosomes FISH |
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Definition
Nondisjunction of sex chromosomes appears to be more frequent than autosomal nondisjunction
Sperm ____ evaluate proportion of normal and abnormal (balanced, unbalanced) sperm in male carriers of reciprocal translocations
50% of sperm have unbalanced karyotypes |
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