Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
37 Cards in this Set
- Front
- Back
Differentiate between constitutional and acquired chromosome abnormalities.
|
constitutional: arise before, at, or very shortly after conception
acquired: in somatic cells, some time after conception, in child or adult) |
|
Define aneuploidy.
|
added or missing chromosomes
|
|
Define metacentric, submetacentric, and acrocentric.
|
metacentric- if two arms of chromatids are of relatively equal length
submetacentric- if one arm is distinctly shorter than the other acrocentric- very short p arms which contain specialized structures, called STALKS |
|
What is unique to acrocentric chromosomes and which chromosomes are they?
|
contain stalks, tandem repeats of ribosomal DNA sequences.
13, 14, 15, 21, 22 |
|
Define nucleolar organizing regions (NOR).
|
also known the stalk regions, because they interact to form the nucleolus
|
|
What are satellites?
|
They are distal to the stalk and contain highly repetitive DNA (with no known coding sequences).
|
|
List several sample types that one can obtain for clinical cytogenetics.
|
bone marrow, peripheral blood, fibroblast, amniotic fluid, chorionic villus (extraembryonic tissue)
|
|
What are the two requirements of a cell type for their chromosomes to be studied?
|
1. a nucleus is present
2. the cells are actively dividing |
|
Name the various banding methods. Which banding method is the most commonly used for cytogenetics?
|
Q-banding, G-banding, C-banding.
G-banding most commonly used. |
|
What is Q-banding, include the name of the dye.
|
Quinacrine, a dye, is used to produce a banding pattern of chromosomes--requires fluorescence microscopy with UV light. A-T rich sequences stain brightly.
|
|
What is G-banding and what is used in this staining?
|
trypsin used to give staining pattern for each chromosome. Giemsa produces pattern of alternating light and dark bands
|
|
What is C-banding mainly used for and how does it stain?
|
used mainly for staining centromeres of chromosomes; heterochromatin (highly repetitive DNA with no coding sequences) stained dark and euchromatin (regions of coding sequences) stained light.
|
|
What is fluoresence in situ hybridization (FISH) and what is it the method of choice for?
|
DNA probe labelled with biotin or digoxigenin to identify chromosomes or to identify deletions for a particular syndrome.
Method of choice for diagnosis of microdeletion and microduplication syndromes. |
|
Name the different types of probes used and briefly describe them.
|
SINGLE COPY/LOCUS SPECIFIC PROBES- used for specific questions regarding number, presence, integrity, absence or location of a unique DNA sequence
SUB-TELOMERE-SPECIFIC PROBE- LOOKS FOR TELOMERES? ALPHOID/CENTROMERIC REPEAT PROBE- help identify specific chromosomes with a satellite DNA ( WHOLE CHROMOSOME PROBES- used to "paint" a whole chromosome or whole chr. arm |
|
New molecular cytogenics allows for what? What is it useful for?
|
simultaneous "painting" of all chromosomes, each with a distinct color--- allows inspection of the entire genome and useful for the study of complex chromosomal rearrangements in cancer patients.
|
|
What is comparative genome microarray analysis?
|
targets the detection of chromosomal abnormalities by performing hundreds of DNA hybridizations at once to detect small chromosome imbalances in one experiment
|
|
Name the different types of numerical chromosome abnormalities.
|
trisomies (47 chr.), monosomies (45 chr.), triploidy (69 chr.), tetraploidy (92 chr.)
|
|
What is the most common trisomy at conception?
|
trisomy 16
|
|
What is the most common monosomy? What is this syndrome called?
|
45, X (Turner Syndrome)
|
|
Define the concept of mosaicism. Often seen in numerical chromosome abnormalities or structural chromosome abnormalities?
|
When two or more cell lines in an individual get mixed together, as a result of mitotic nondisjunction. Somatic mosaicism leads to an abnormal phenotype.
Often seen on numerical chr. abn. |
|
Most cancers are initiated by which type of chromosome abnormality? (constitutional or acquired)
|
acquired
|
|
Define terminal deletion.
|
one break in one chromosome arm.
|
|
What is the most common and first described terminal deletion in humans?
|
5p-syndrome (Cri-du-chat syndrome)
|
|
Define interstitial deletions. Name some common microdeletion syndromes.
|
two breaks in one chromosome arm. then the two sticky ends rejoin.
common syndromes: Prader-Willi syndrome, DiGeorge syndrome, Williams syndrome, Smith-Magenis syndrome |
|
Define reciprocal translocations
|
if two breaks occur in two different chromosomes at same time-- broken ends exchange and rejoin
|
|
Does a balanced rearrangement (alternate segregation) have phenotypic consequences?
|
no, but these individuals are at risk for producing abnormal gametes through segregation errors in meiosis
|
|
What is malsegregation?
|
adjacent segregation where adjacent centromeres of chromosomes that have undergone reciprocal translocations travel together (adjacent-1 or adjacent-2). These typically have more severe consequences.
|
|
What is a Robertsonian translocation?
|
special class of translocations that form between two acrocentric chromosomes (13, 14, 15, 21, 22).
|
|
What is the genetic defect in Down's Syndrome?
|
Trisomy 21
|
|
What is an inversion?
|
two breaks in one chromosome. The piece between the breaks inverts and rejoins.
|
|
In an inversion, what is the clinical outcome?
|
since it is balanced rearrangement and no chromosomal material is gained/lost, this produces no abnormal phenotype.
|
|
What is the major factor contributing to numerical abnormalities? What syndrome is the one exception?
|
Advanced maternal age
exception: Turner syndrome (chromosome being lost most likely from father) |
|
Define non-disjunction
|
aberrant segregation of homologous chromosomes into the same daughter cell (ie. at meiosis I or II)
|
|
Dispermy is the most common cause of triploidy. What is dispermy?
|
when an ovum is fertilized by TWO SPERM to yield a triploid zygote
|
|
In terms of inversions, what is pericentric and paracentric?
|
pericentric- 2 breaks on either side of the centromere; involves centromere
paracentric- does not involve centromere bc two breaks on same arm of chromosome |
|
What are the results of recombination in pericentric vs. paracentric inversions? Talk about viability of products.
|
pericentric- duplication deficiency chromosomes; LARGER THE INVERSION, THE MORE VIABLE IT IS
paracentric- acentric (no centromeres) and dicentric (two centromeres) chromosomes; PRODUCTS NOT VIABLE (MISCARRIAGE) |
|
Define cryptic chromosome abnormalities
|
telomeric rearrangements that lead to mental retardation
|