Philadelphia chromosome

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in animal cells, a structure in the nucleus, containing a linear thread of deoxyribonucleic acid (DNA), which transmits genetic information and is associated with ribonucleic acid and histones. In bacterial genetics, a closed circle of double-stranded DNA that contains the genetic material of the cell and is attached to the cell membrane; the bulk of this material forms a compact bacterial nucleus. adj., adj chromoso´mal.

During cell division the material composing the chromosome is compactly coiled, making it visible with appropriate staining and permitting its movement in the cell with minimal entanglement. Each organism of a species is normally characterized by the same number of chromosomes in its somatic cells, 46 being the number normally present in humans, including 22 pairs of autosomes and the two sex chromosomes (XX or XY), which determine the sex of the organism. (See also heredity.)
Chromosome Analysis. This can be done on fetal cells obtained by amniocentesis or chorionic villus sampling, on lymphocytes from a blood sample, on skin cells from a biopsy, or on cells from products of conception such as an aborted fetus. The cells are then cultured in the laboratory until they divide. Cell division is arrested in mid-metaphase by the drug Colcemid. The chromosomes can be stained by one of several techniques that produce a distinct pattern of light and dark bands along the chromosomes, and each chromosome can be recognized by its size and banding pattern. The chromosomal characteristics of an individual are referred to as the karyotype. It is also possible to make a photomicrograph of a cell nucleus, cut it apart, and rearrange it so that the individual chromosomes are in order and labeled. The autosomes are numbered 1–22, roughly in order of decreasing length. The sex chromosomes are labeled X and Y. Karyotyping is useful in determining the presence of chromosome defects.

Before the chromosomes could be precisely identified they were placed in seven groups: A (chromosomes 1–3), B (4–5), C (6–12 and X), D (13–15), E (16–18), F (19–20), and G (21–22 and Y).
Chromosomal Abnormalities. The prevalence of chromosomal disorders cannot be fully and accurately determined because many of these disorders do not permit full embryonic and fetal development and therefore end in spontaneous abortion. About one in every 100 newborn infants do, however, have a gross demonstrable chromosomal abnormality. A large majority of cytogenetic abnormalities can be identified by cytogenetic analysis either before birth, by means of chorionic villus sampling or amniocentesis, or after birth.

Cytogenetic disorders with visible chromosomal abnormalities are evidenced by either an abnormal number of chromosomes or some alteration in the structure of one or more chromosomes. In the language of the geneticist, trisomy refers to the presence of an additional chromosome that is homologous with one of the existing pairs so that that particular chromosome is present in triplicate. An example of this type of disorder is a form of down syndrome (trisomy 21). Another example is patau's syndrome (trisomy 13), which produces severe anatomical malformations and profound mental retardation.

The term monosomy refers to the absence of one of a pair of homologous chromosomes. Monosomy involving an autosome usually results in the loss of too much genetic information to permit sufficient fetal development for a live birth. Either trisomy or monosomy involving the sex chromosomes yields relatively mild abnormalities.

A condition known as mosaicism results from an error in the distribution of chromosomes between daughter cells during an early embryonic cell division, producing two and sometimes three populations of cells with different chromosome numbers in the same individual. Mosaicism involving the sex chromosomes is not uncommon.

Other abnormal structural changes in the chromosome are consequences of some kind of chromosomal breakage, with either the loss or rearrangement of genetic material. translocation involves the transfer of a segment of one chromosome to another. inversion refers to a change in the sequence of genes along the chromosome, which occurs when there are two breaks in a chromosome and the segment between the breaks is reversed and reattached to the wrong ends. deletion occurs when a portion of a chromosome is lost. An example of this type of chromosomal abnormality is cri du chat syndrome, a deletion in the short arm of chromosome 5, marked by mental retardation and sometimes congenital heart defects. When deletion occurs at both ends of the chromosome, the two damaged ends can unite to form a circle and the rearrangement produces a ring chromosome. isochromosomes form when the centromere divides along the transverse plane rather than the normal long axis of the chromosome so that both arms are identical. All of the previously described structural abnormalities can affect both autosomal and sex chromosomes.

The causes of chromosomal errors are not completely understood. In some conditions such as Down syndrome, late maternal age seems to be a factor. Other factors may include the predisposition of chromosomes to nondisjunction (failure to separate during meiosis), exposure to radiation, and viruses.
homologous c's the chromosomes of a matching pair in the diploid complement that contain alleles of specific genes.
Ph1 chromosome (Philadelphia chromosome) an abnormality of chromosome 22, characterized by the translocation of genetic material from its long arm to chromosome 9, seen in the marrow cells of most patients with chronic myelogenous leukemia.
ring chromosome a chromosome in which both ends have been lost (deletion) and the two broken ends have reunited to form a ring-shaped figure.
sex c's the chromosomes responsible for determination of the sex of the individual that develops from a zygote; in mammals they are an unequal pair, the X and Y chromosomes.
somatic chromosome autosome.
X chromosome the female sex chromosome, being carried by half the male gametes and all female gametes; female diploid cells have two X chromosomes.
Y chromosome the male sex chromosome, being carried by half the male gametes and none of the female gametes; male diploid cells have an X and a Y chromosome.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

Phil·a·del·phi·a chro·mo·some (Ph1),

an abnormally shortened chromosome 22, formed by translocation of a portion of the long arm of chromosome 22 to chromosome 9; found in cultured leukocytes of many patients with chronic granulocytic leukemia.
Farlex Partner Medical Dictionary © Farlex 2012

Philadelphia chromosome

An abnormal chromosome formed by a reciprocal translocation between chromosomes 9 and 22, found in the white blood cells of people with chronic myelogenous leukemia and causing abnormal activity of a form of tyrosine kinase.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.
A small acrocentric chromosome from the distal long—q arm of chromosome 22, transferred to chromosome 9q[t(9;22)(q34;q11)] in 95% of chronic myeloid leukaemia; PC is also present in 3% to 5% of childhood acute lymphocytic leukaemia, for whom the prognosis is poor, and 25% of adults
Origin of PC Pluripotent stem cell, which generates myeloid, erythroid, megakaryocytic and lymphoid lines
Management High-dose chemotherapy, Bone marrow transplantation
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

Philadelphia chromosome

A small acrocentric chromosome from the distal long–q arm of chromosome 22, transferred to chromosome 9q[t(9;22)(q34;q11)] in 95% of CML; PC is present in 3 to 5% of childhood ALL–for whom prognosis is poor, and 25% of adults Origin of PC Pluripotent stem cell, which generates myeloid, erythroid, megakaryocytic and lymphoid lines Molecular pathology Reciprocal translocation, with juxtaposition of the c-abl gene on chromosome 9 with a gene of unknown function, with a bcr–breakpoint cluster region on chromosome 22; the resulting hybrid abl/bcr gene encodes P210bcr/abl, a phosphoprotein unique to CML that resembles v-abl, as it has disregulated protein-tyrosine kinase activity Management High-dose chemotherapy, BMT. See P210bcr/abl.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.

Phil·a·del·phi·a chro·mo·some

(fil'ă-del'fē-ă krō'mŏ-sōm)
An abnormal minute chromosome. Formed by a rearrangement of chromosomes 9 and 22; found in cultured leukocytes of many patients with chronic granulocytic leukemia.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

Philadelphia chromosome

An acquired chromosomal defect in which the long arm of chromosome 22 is deleted and attached (translocated) to another chromosome, usually number 9. Clones of cells with this defect cause chronic myeloid LEUKAEMIA.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005

Philadelphia chromosome

An abnormal chromosome that is found in patients with a chronic form of leukemia but not in PV patients.
Mentioned in: Polycythemia Vera
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.


city in Pennsylvania.
Philadelphia chromosome - an abnormal minute chromosome formed by a rearrangement of chromosomes 9 and 22.
Philadelphia cocktail - Synonym(s): Rivers cocktail
Philadelphia collar - head and neck orthosis.
Medical Eponyms © Farlex 2012
References in periodicals archive ?
The atypical patterns observed in the Indian population include deletions of derivative 9 involving chromosome 9 sequences, chromosome 22 sequences, both; additional Philadelphia chromosome and more than one signal pattern while in our population only two variant patterns were observed.
Historically, CML was the first MPN to have a known acquired chromosomal abnormality, a reciprocal translocation between the long arms of chromosomes 9 and 22 known as the Philadelphia chromosome (Ph1) and designated as t(9;22)(q34;q11).
Detection of Philadelphia chromosome using PCR and europium-labeled DNA probes.
Alternately, the Philadelphia chromosome that was present in the 7/17 cells with the persistent del(20q) could represent a subclone.
The trial, which will be conducted across multiple sites in the United States, Asia and Europe, will evaluate BOSULIF, administered at a starting dose level of 400 mg daily, as a first-line treatment for patients with chronic phase Philadelphia chromosome positive (Ph+) chronic myelogenous leukemia (CML).
Application of Chromosome Microdissection Probes for Elucidation BCR-ABL Fusion and Variant Philadelphia Chromosome Translocations of in Chronic Myelogenous Leukemia.
The discovery of the Philadelphia chromosome as a hallmark of chronic myelogenous leukemia in 1960 began a new era in hematopathology in which new ancillary studies, cytogenetics in particular, played an increasingly important diagnostic role.
Cytogenetic response: a goal of treatment; refers to the elimination of cells that have the Philadelphia chromosome mutation
Amgen announced that the Committee for Medicinal Products for Human Use of the European Medicines Agency has adopted a positive opinion to expand the current indication for BLINCYTO monotherapy to include adult patients with Philadelphia chromosome negative CD19 positive B-cell precursor acute lymphoblastic leukemia in first or second complete remission with minimal residual disease greater than or equal to 0.1%.
Chemke, "Philadelphia chromosome in idiopathic acquired sideroblastic anemia," Acta Haematologica, vol.
According to Helbig et al ., [sup][8] high risk (HR) was defined as having any of the following poor-risk factors: (1) Age ≥35 years, (2) high white blood cell (WBC) count (>30 x 10 [sup]9 /L for B-cell lineage and >100 x 10 [sup]9 /L for T-cell lineage), (3) pro-B, early-T and mature T immunophenotype, (4) second or greater complete remission (CR), (5) the presence of adverse cytogenetics: Philadelphia chromosome positive (Ph-positive), that is, t(9;22) and/or BCR-ABL transcripts; 11q23 abnormality and/or MLL-AF4 transcripts; t(1;19) and/or E2A-PBX1 transcripts; complex karyotype and hypodiploidity.

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