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44 Cards in this Set
- Front
- Back
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... is the study of chromosomes, their structure and their inheritance.
Genome and chromosomal disorders are distinguished by this. |
Cytogenetics
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What is this?
representive drawing of each of the chromosomes there are 24 different types of chromosomes found in the human genome -22 autosomes number 1-22 -two sex chromosomes X (female) and Y (male) Remember! Chromosomes are typically represented with the sister chromatids so closely aligned they are not recognized are distinct entities |
Karyogram
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Classifications of chromosomes
based on position of ... distinguished at ... ... is the short arm ... is the long arm |
centrosome
metaphase p q |
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classifications:
1. ... - more or less central centromere with arms of approximately equal length |
Metacentric
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classification:
2. ... - off-center centromere and arms of different length |
Submetacentric
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classification:
3. ... -chromosomes 13, 14, 15, 21 and 22 -centromere near one end -small, distinctive masses of chromatin known as satellites attached to their short arms by narrow constrictions (secondary constrictions) -stalks contain hundreds of copies of gene encoding ribosomal rRNA and a variety of repetitive sequences |
Acrocentric
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Chromosomes are grouped according to ... and ... of centromere.
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size
position |
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What is this?
needed to accurately identify characteristic patterns of individual chromosomes -size and position of centromere not enough to distinguish |
Chromosome Analysis
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What are these?
Chromosome Banding-Karyotyping In-situ Hybridization Comparative Genomic Hybridization |
Methods of chromosome analysis
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Karyotype
microphotograph of the ... constitution of an individual most easily visualized during ..., when the chromosomes are maximally expressed a typical somatic cell displays ... pairs of human chromosomes -both copies of each autosome -copy of each sex chromosome X,X or X,Y ordered according to ... -sex chromosomes placed in ... portion |
chromosome
metaphase 23 size lower right |
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Chromosome banding
application of different stains result in ... patterns that allow for visualization of individual chromosomes in karyotype most commonly used is G (Giemsa) Banding -chromosomes are treated with ... to denature DNA associated proteins -followed by staining with ..., binds specifically to DNA -staining reveals a characteristic and reproducible pattern of light and dark regions (...) that allows for accurate identification of individual chromosomes |
banding
trypsin Giemsa G-regions |
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Utility
used to identify any gross chromosomal ..., such as a large deletion/insertion (>4Mb), inversions, ring chromosomes, translocations and aneuploidies smaller anomalies identified using FISH or CGH |
abnormality
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Fragile sites
non-staining ... occasionally observed at characteristic sites on several chromosomes heritable variants most clinically significant fragile site seen near the end of ... in males, as well as some female carriers originally detected using basic ... techniques -detection now replaced by molecular testing unstable repeat expansion |
gaps
Xq staining |
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Fragile X syndrome
-specific and common form of ... mental retardation -second only to Down syndrome for mental retardation in males -caused by an ..., CGG, in the 5’ untranslated region of the first exon of the gene called FMR-1 (Fragile X mental retardation-1) -leads to excessive methylation of ... in promoter, an epigenetic modification of DNA that silences transcription from the gene |
X-linked
unstable repeat expansion cytosines |
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What is this called?
-where molecular techniques and traditional cytogenetics collide! -based on the ability of single-stranded DNA probes to hybridize to complementary target sequences on a metaphase spreads (think cytogenetic Southern blotting) -the probed is fluorescently labelled and hybridized with the patient’s chromosomes -hybridization is visualized using a fluorescence microscope |
Fluorescence in situ Hybridization (FISH)
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FISH: Advantage over chromosome banding:
chromosomes do not need to be in ... stage for accurate diagnosis -count hybridization signals in interphase and prophase without visualization of individuals chromosomes -... aneuploidies, small deletions/insertions, duplications, some inversions, ring chromosomes and translocations |
metaphase
detects |
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Comparative Genomic Hybridization
molecular/cytogenetic method for the detection of ... changes -allele loss and gene ... -well suited for the analysis of ... samples |
copy number
amplification tumor |
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Comparative Genomic Hybridization
utilizes ... techniques -two probes fluorescently labeled -tumor or patient DNA fluorescently labeled ... (FITC) -normal DNA fluorescently labeled ... (DAPI) -two probes allowed to mix and hybridized to a ... metaphase spread -analyzed my ... microscopy -increase in green to red fluorescence ratio indicates gene ... -reduction in green to red fluorescence ratio indicates a ... |
FISH
green red NORMAL fluorescence amplification loss of allele |
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chromosome nomenclature:
Chromosome is divided into ... Each region subdivided into ... Numbering always begins from the ... and goes outward |
regions
bands centromere |
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Chromosome nomenclature
Designation of a ... on a chromosome -chromosome number is given ... -then the ..., p or q -followed by the ... and the ... Sometimes region and band are combined and just referred to as the band |
point
first arm region band |
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Designation of Karyotypes
-descriptors of normal karyotypes and karyotypes of aneuploidies and chromosomal abnormalities Normal male karyotype ... Normal female karyotype ... Male with Down syndrome (Trisomy 21) ... Male with a duplication of the q21 band on chromosome 21 ... or ... Male with a translocation between chromosomes 2 and 4 at points p23 and q25, respectively ... |
46,XY
46,XX 47,XY,+21 46,XY,dup(21)(q21q21) 46dup(21)(q21) 46,XY,t(2;4)(p23;q25) |
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What type of cytogenic abnormalities is each one?
... Translocations: reciprocal or Robertsonian Deletions/Insertions Duplications Inversions: pericentric or paracentric Rings Isochromosomes ... Aneuploidy: Autosomal or Sex chromosome Euploidy/Polyploidy ... Mosaicism |
Structural
Numerical Different Cell Lines |
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Structural Abnormalities
... if chromosome set has normal complement of chromosomal material ... if chromosome set has gained or lost additional material some are stable enough to pass through mitosis and meiosis unaltered -rearranged chromosome must have a functional ... and two ... |
balanced
unbalanced centromere telomeres |
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NOTE: Structural abnormalities tend not to harm the carrier, ... are normally impacted by the abnormality.
-clinical presentation dependent on what chromosome(s) are involved and the gene(s) are disrupted |
offspring
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... -exchange between two, usually non-homologous, chromosomes
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Translocations
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Two types of translocations:
1. Reciprocal -breakage of two non-homologous chromosomes followed by reciprocal exchange of fragments -total number of chromosomes remains 46 -carrier phenotypically normal -translocation between the long arms of ... and ... is very common -a common reciprocal translocation occurs between chromosomes 9 and 22 forming the ... chromosome -fusion of the bcr and abl genes that encode a protein with deregulated tyrosine kinase activity -Philadelphia chromosome predispose an individual to chronic myelogenous leukemia (CML), acute lymphoblastic leukemia (ALL), and acute myelogenous leukemia (AML) 2. ... |
11
22 Philadelphia Robertsonian |
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Formation of a ...
pairing of the chromosomes of a carrier of a balanced reciprocal translocation during meiosis unable to form bivalents, the chromosomes align homologous material into a ... |
Quadrivalent
quadrivalent |
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During anaphase, chromosomes separate from the quadrivalent configuration in one of three 2:2 Segregations
1. ... segregation (usual type of segregation) -balanced -gametes have the normal complement of chromosomes OR two reciprocal chromosome 2. ... -unbalanced -homologous centromeres go to separate daughter cells -normally seen in meiosis I 3. ... -unbalanced -homologous centromeres go to same daughter cells ... is also observed leading to gametes with 22 or 24 chromosomes |
Alternate
Adjacent 1 Adjacent 2 Non-disjunction |
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... Translocations
involves two acrocentric chromosomes fusion near centromere region resulting in loss of the short (p) arms -REMEMBER! short arms of acrocentric chromosomes contain gene copies for rRNA; loss is not detrimental total chromosome number is reduced to ... -includes the translocation chromosome which made up of two chromosomes involves all combinations of acrocentric chromosomes; 13q14q and 14q21q being the most common carriers phenotypically normal |
Robertsonian
45 |
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NOTE: Carrier of a 21q21q Robertsonian translocation will either be ... or ... for chromosome 21, resulting in spontaneous miscarriage or birth of a child with Down syndrome
Import lies in their behavior at meiosis |
nullisomic
disomic |
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Possible gametes if translocation between chromosome 14 and 21
1. ... chromosome complement 2. ... chromosome complement (robertsonian translocation) -normal carrier 3. Unbalanced chromosome complement (robertsonian translocation and normal ...) -results in Down syndrome 4. Unbalanced chromosome complement (normal ... and missing 21) 5. Unbalanced chromosome complement (normal ... and missing 14) 6. Unbalanced chromosome complement (robertsonian translocation and normal 14) Final three are incompatible with life |
Normal
Balanced 21 14 21 |
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Robertsonian translocation involving chromosome 21 predispose to ...
-inherit two normal 21 chromosomes and Robertsonian translocation involving chromosome 21 -parent is a carrier, high risk of having multiple affected children |
Down syndrome
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Deletions, Insertions, and Duplications
-... of the overall number of chromosomes (46) |
maintenance
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Deletions
... of chromosome segment, resulting in chromosome imbalance -terminal or interstitial carrier is ... for genetic information on the normal homologue (hemizygous at that particular locus) clinical consequence is ... -inability of a single gene copy to carry out the functions normally performed by two copies results from chromosomal ... and loss OR unequal crossing over |
loss
monosomic haploinsufficiency breakage |
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Insertions
insertion of a segment of one chromosome into another chromosome ... if the inserted material has moved from elsewhere in another chromosome -insertions usually create a ... in another chromosome -gamete will inherit either the insertion or the deletion results from ... crossing over |
balanced
deletion unequal |
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...
originates by unequal crossing over or abnormal segregation form meiosis in a carrier of a translocation or inversion abnormalities result from chromosomal imbalance; partial trisomy chromosomal breaks may disrupt genes |
Duplications
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Inversions
single chromosome undergoes two breaks and is reconstituted when the segment between the breaks is ... neither pericentric or paracentric inversions cause an ... carrier because these are balanced rearrangements -exception is if the break ... a gene |
inverted
abnormal disrupts |
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Two types of inversions:
1. ... -including the centromere -break in each arm -... inversion in chromosome 9 is a common structural polymorphism 2. ... -does not include the centromere -both breaks occur in one arm |
Pericentric
pericentric Paracentric |
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Pericentric and Paracentric Inversions
problems arise during ... during meiosis gametes receive balanced and unbalanced recombinant chromosomes from crossing over events during meiosis I in an attempt to maintain homologous pairing at synapsis, an ... is formed with both pericentric and paracentric inversions, two gametes have balanced recombinant chromosomes -one normal and one containing the inversion with pericentric inversions, two gametes have ... complements with paracentric inversions, the gametes have unbalanced complements -one typically acentric -the other dicentric -offspring is (viable or not viable?) |
crossing over
inversion loop unbalanced not viable |
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Ring Chromosomes
formed when a chromosome undergoes two breaks and the broken or “sticky” ends of the chromosome ... to form a ring ..., but have been detected for every chromosome if centromere present, mitotically ... difficulties arise during anaphase with the ... of sister chromatid and ring chromosome -ring chromosome found only in a small proportion of cells |
reunite
rare stable tangling |
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Isochromosomes
chromosome in which one arm is missing and the other is duplicated creating a ... image an individual carrying an isochromosome has a single copy of the genetic material one arm (partial ...) and three copies of the genetic material of the other arm (partial ...) proposed mechanism is the misdivision through the centromere, transversely rather than longitudinally, during ... -presence of two centromere; ... chromosomes most common is the isochromosome of the long arm of the X chromosome, i(Xq) -know to be the cause of some cases of ... Syndrome |
mirror
monosomy trisomy meiosis II isodicentric Turner |
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which of the following classes of chromosomes contain rRNA and repetitive sequences in their p arms?
acrocentric metacentric submetacentric |
acrocentric
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which of the following is a karyotype of a male with a translocation between chromosomes 7 and 20 at band q21 and q12 respectively?
46,XX,t(7;20)(q21;q12) 46,XY,t(7;20)(q21;q12) 46,XY,t(7;20)(q12;q21) |
46,XY,t(7;20)(q21;q12)
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Pericentric inversions include the centromere and a break in each arm of the chromosome.
True or False? |
true
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