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Section: Mechanism > Cycle of X-chromosome activation in rodents > Overview. The Xi marks the inactive, Xa the active X chromosome. XP denotes the paternal, and XM to denotes the maternal X chromosome. When the egg (carrying XM), is fertilized by a sperm (carrying a Y or an XP) a diploid zygote forms. From zygote, thro... | Wikipedia - X-inactivation - Mechanism > Cycle of X-chromosome activation in rodents > Overview | 339 | 1,363 | null |
Section: Mechanism > Cycle of X-chromosome activation in rodents > Overview > Inheritance of inactivation status across cell generations. The descendants of each cell which inactivated a particular X chromosome will also inactivate that same chromosome. This phenomenon, which can be observed in the coloration of tortoi... | Wikipedia - X-inactivation - Mechanism > Cycle of X-chromosome activation in rodents > Overview > Inheritance of inactivation status across cell generations | 183 | 861 | null |
Section: Mechanism > Selection of one active X chromosome. Typical females possess two X chromosomes, and in any given cell one chromosome will be active (designated as Xa) and one will be inactive (Xi). However, studies of individuals with extra copies of the X chromosome show that in cells with more than two X chromo... | Wikipedia - X-inactivation - Mechanism > Selection of one active X chromosome | 338 | 1,659 | null |
Preferential inactivation of the paternal X-chromosome occurs in both marsupials and in cell lineages that form the membranes surrounding the embryo, whereas in placental mammals either the maternally or the paternally derived X-chromosome may be inactivated in different cell lines. The time period for X-chromosome ina... | Wikipedia - X-inactivation - Mechanism > Selection of one active X chromosome | 341 | 1,667 | null |
It is hypothesized that there is an autosomally-encoded 'blocking factor' which binds to the X chromosome and prevents its inactivation. The model postulates that there is a limiting blocking factor, so once the available blocking factor molecule binds to one X chromosome the remaining X chromosome(s) are not protected... | Wikipedia - X-inactivation - Mechanism > Selection of one active X chromosome | 156 | 735 | null |
Section: Mechanism > Expression of X-linked disorders in heterozygous females. The effect of female X heterozygosity is apparent in some localized traits, such as the unique coat pattern of a calico cat. It can be more difficult, however, to fully understand the expression of un-localized traits in these females, such ... | Wikipedia - X-inactivation - Mechanism > Expression of X-linked disorders in heterozygous females | 319 | 1,478 | null |
There are many different ways in which the phenotypic variation can play out. In many cases, heterozygous females may be asymptomatic or only present minor symptoms of a given disorder, such as with X-linked adrenoleukodystrophy. The differentiation of phenotype in heterozygous females is furthered by the presence of X... | Wikipedia - X-inactivation - Mechanism > Expression of X-linked disorders in heterozygous females | 337 | 1,455 | null |
Section: Mechanism > Xist and Tsix RNAs. The X-inactive specific transcript (Xist) gene encodes a large non-coding RNA that is responsible for mediating the specific silencing of the X chromosome from which it is transcribed. The inactive X chromosome is coated by Xist RNA, whereas the Xa is not (See Figure to the righ... | Wikipedia - X-inactivation - Mechanism > Xist and Tsix RNAs | 334 | 1,471 | null |
Section: Mechanism > Silencing. The inactive X chromosome does not express the majority of its genes, unlike the active X chromosome. This is due to the silencing of the Xi by repressive heterochromatin, which compacts the Xi DNA and prevents the expression of most genes. Compared to the Xa, the Xi has high levels of D... | Wikipedia - X-inactivation - Mechanism > Silencing | 206 | 829 | null |
Section: Mechanism > Barr bodies > Expressed genes on the inactive X chromosome. A fraction of the genes along the X chromosome escape inactivation on the Xi. The Xist gene is expressed at high levels on the Xi and is not expressed on the Xa. Many other genes escape inactivation; some are expressed equally from the Xa ... | Wikipedia - X-inactivation - Mechanism > Barr bodies > Expressed genes on the inactive X chromosome | 349 | 1,631 | null |
The existence of genes along the inactive X which are not silenced explains the defects in humans with atypical numbers of the X chromosome, such as Turner syndrome (X0, caused by SHOX gene) or Klinefelter syndrome (XXY). Theoretically, X-inactivation should eliminate the differences in gene dosage between affected ind... | Wikipedia - X-inactivation - Mechanism > Barr bodies > Expressed genes on the inactive X chromosome | 192 | 886 | null |
Section: Uses in experimental biology. Stanley Michael Gartler used X-chromosome inactivation to demonstrate the clonal origin of cancers. Examining normal tissues and tumors from females heterozygous for isoenzymes of the sex-linked G6PD gene demonstrated that tumor cells from such individuals express only one form of... | Wikipedia - X-inactivation - Uses in experimental biology | 346 | 1,610 | null |
Section: History. In 1959 Susumu Ohno showed that the two X chromosomes of mammals were different: one appeared similar to the autosomes; the other was condensed and heterochromatic. This finding suggested, independently to two groups of investigators, that one of the X chromosomes underwent inactivation. In 1961, Mary... | Wikipedia - X-inactivation - History | 231 | 1,058 | null |
Article: X-linked recessive inheritance. Main Article: Sex linkage X-linked recessive inheritance is a mode of inheritance in which a mutation in a gene on the X chromosome causes the phenotype to be always expressed in males (who are necessarily hemizygous for the gene mutation because they have one X and one Y chromo... | Wikipedia - X-linked recessive inheritance - Summary | 235 | 1,073 | null |
Section: Patterns of inheritance. In humans, inheritance of X-linked recessive traits follows a unique pattern made up of three points. The first is that affected fathers cannot pass X-linked recessive traits to their sons because fathers give Y chromosomes to their sons. This means that males affected by an X-linked r... | Wikipedia - X-linked recessive inheritance - Patterns of inheritance | 287 | 1,456 | null |
Section: Examples > Most common. The most common X-linked recessive disorders are: Red–green color blindness, also known as daltonism, which affects roughly 7% to 10% of men and 0.49% to 1% of women. Its relative benignity may explain its commonness. Hemophilia A, a blood clotting disorder caused by a mutation of the F... | Wikipedia - X-linked recessive inheritance - Examples > Most common | 343 | 1,422 | null |
X-linked agammaglobulinemia (XLA), which affects the body's ability to fight infection. XLA patients do not generate mature B cells. B cells are part of the immune system and normally manufacture antibodies (also called immunoglobulins) which defends the body from infections (the humoral response). Patients with untrea... | Wikipedia - X-linked recessive inheritance - Examples > Most common | 160 | 694 | null |
Section: Examples > Less common disorders. Theoretically, a mutation in any of the genes on chromosome X may cause disease, but below are some notable ones, with short description of symptoms: Adrenoleukodystrophy; leads to progressive brain damage, failure of the adrenal glands, and eventually death. Alport syndrome; ... | Wikipedia - X-linked recessive inheritance - Examples > Less common disorders | 338 | 1,532 | null |
Coffin–Lowry syndrome; severe intellectual disability sometimes associated with abnormalities of growth, cardiac abnormalities, and kyphoscoliosis as well as auditory and visual abnormalities. Fabry disease; A lysosomal storage disease causing anhidrosis, fatigue, angiokeratomas, burning extremity pain, and ocular invo... | Wikipedia - X-linked recessive inheritance - Examples > Less common disorders | 168 | 725 | null |
Hypohidrotic ectodermal dysplasia, presenting with hypohidrosis, hypotrichosis, and hypodontia Kabuki syndrome (the KDM6A variant); multiple congenital anomalies and intellectual disability. Lesch–Nyhan syndrome; neurologic dysfunction, cognitive and behavioral disturbances including self-mutilation, and uric acid over... | Wikipedia - X-linked recessive inheritance - Examples > Less common disorders | 247 | 1,016 | null |
Lesch–Nyhan syndrome; neurologic dysfunction, cognitive and behavioral disturbances including self-mutilation, and uric acid overproduction (hyperuricemia) Lowe syndrome; hydrophthalmia, cataracts, intellectual disabilities, aminoaciduria, reduced renal ammonia production, and vitamin D-resistant rickets Menkes disease... | Wikipedia - X-linked recessive inheritance - Examples > Less common disorders | 430 | 1,813 | null |
Article: X:A ratio. The X:A ratio is the ratio between the number of X chromosomes and the number of sets of autosomes in an organism. This ratio is used primarily for determining the sex of some species, such as drosophila flies and the C. elegans nematode. The first use of this ratio for sex determination is ascribed... | Wikipedia - X:A ratio - Summary | 223 | 865 | null |
Article: Ecogenetics. Ecogenetics is a branch of genetics that studies genetic traits related to the response to environmental substances. Or, a contraction of ecological genetics, the study of the relationship between a natural population and its genetic structure. Ecogenetics principally deals with effects of preexis... | Wikipedia - Ecogenetics - Summary | 326 | 1,663 | null |
Red blood cell conditions There is a broad group of genetic diseases that result in either producing or predisposing affected individuals to the development of hemolytic anemias. These diseases include abnormal haemoglobin, inability to manufacture one or the other of the peptide globin chains of the haemoglobin, and d... | Wikipedia - Ecogenetics - Summary | 249 | 1,201 | null |
Section: History > Beginnings. Chromosomes were first observed in plant cells by Carl Nägeli in 1842. Their behavior in animal (salamander) cells was described by Walther Flemming, the discoverer of mitosis, in 1882. The name was coined by another German anatomist, von Waldeyer in 1888. The next stage took place after ... | Wikipedia - Cytogenetics - History > Beginnings | 291 | 1,354 | null |
Section: Applications of cytogenetics > McClintock's work on maize. Barbara McClintock began her career as a maize cytogeneticist. In 1931, McClintock and Harriet Creighton demonstrated that cytological recombination of marked chromosomes correlated with recombination of genetic traits (genes). McClintock, while at the... | Wikipedia - Cytogenetics - Applications of cytogenetics > McClintock's work on maize | 188 | 862 | null |
Section: Applications of cytogenetics > Natural populations of Drosophila. In the 1930s, Dobzhansky and his coworkers collected Drosophila pseudoobscura and D. persimilis from wild populations in California and neighboring states. Using Painter's technique they studied the polytene chromosomes and discovered that the w... | Wikipedia - Cytogenetics - Applications of cytogenetics > Natural populations of Drosophila | 269 | 1,334 | null |
Section: Human abnormalities and medical applications. Following the advent of procedures that allowed easy enumeration of chromosomes, discoveries were quickly made related to aberrant chromosomes or chromosome number. Constitutional cytogenetics: In some congenital disorders, such as Down syndrome, cytogenetics revea... | Wikipedia - Cytogenetics - Human abnormalities and medical applications | 337 | 1,638 | null |
Acquired cytogenetics: In 1960, Peter Nowell and David Hungerford discovered a small chromosome in the white blood cells of patients with Chronic myelogenous leukemia (CML). This abnormal chromosome was dubbed the Philadelphia chromosome - as both scientists were doing their research in Philadelphia, Pennsylvania. Thir... | Wikipedia - Cytogenetics - Human abnormalities and medical applications | 289 | 1,426 | null |
Section: Human abnormalities and medical applications > Advent of banding techniques. In the late 1960s, Torbjörn Caspersson developed a quinacrine fluorescent staining technique (Q-banding) which revealed unique banding patterns for each chromosome pair. This allowed chromosome pairs of otherwise equal size to be diff... | Wikipedia - Cytogenetics - Human abnormalities and medical applications > Advent of banding techniques | 254 | 1,297 | null |
Section: Techniques > Karyotyping. The routine chromosome analysis (Karyotyping) refers to analysis of metaphase chromosomes which have been banded using trypsin followed by Giemsa, Leishmanns, or a mixture of the two. This creates unique banding patterns on the chromosomes. The molecular mechanism and reason for these... | Wikipedia - Cytogenetics - Techniques > Karyotyping | 313 | 1,423 | null |
Section: Techniques > Karyotyping > Slide preparation. Cells from bone marrow, blood, amniotic fluid, cord blood, tumor, and tissues (including skin, umbilical cord, chorionic villi, liver, and many other organs) can be cultured using standard cell culture techniques in order to increase their number. A mitotic inhibit... | Wikipedia - Cytogenetics - Techniques > Karyotyping > Slide preparation | 273 | 1,201 | null |
Article: Achiasmate meiosis. Achiasmate meiosis refers to meiosis without chiasmata, which are structures that are necessary for recombination to occur and that usually aid in the segregation of non-sister homologs. The pachytene stage of prophase I typically results in the formation of chiasmata between homologous non... | Wikipedia - Achiasmate meiosis - Summary | 302 | 1,288 | null |
Section: Known achiasmatic species > Saccharomycodes ludwigii. While multiple species of budding yeast have been found to have residual SC proteins that connect the centromeres together when needed, nearly all of said species are chiasmatic and have been simply used as convenient model organisms. However, Saccharomycod... | Wikipedia - Achiasmate meiosis - Known achiasmatic species > Saccharomycodes ludwigii | 225 | 1,092 | null |
Section: Known achiasmatic species > Amazon Molly. Amazon Mollies (Poecilia formosa) reproduce without recombination via gynogenesis. They mate with males of other species and the sperm triggers the development of their eggs, but the Amazon Mollies create diploid eggs that have copies of only their own genes. There is ... | Wikipedia - Achiasmate meiosis - Known achiasmatic species > Amazon Molly | 162 | 726 | null |
Article: Anaphase lag. Anaphase lag is a consequence of an event during cell division where sister chromatids do not properly separate from each other because of improper spindle formation. The chromosome or chromatid does not properly migrate during anaphase and the daughter cells will lose some genetic information. I... | Wikipedia - Anaphase lag - Summary | 193 | 910 | null |
Section: Mechanisms. There are two notable mechanisms that cause Anaphase Lag, each of which are characterized by merotelic attachments of kinetochores to the microtubules responsible for chromatid separation. Merotelic attachments occur when a single centromere kinetochore attaches to microtubules originating from bot... | Wikipedia - Anaphase lag - Mechanisms | 297 | 1,447 | null |
Section: Genomic causes. The increasing importance of genomic instability on cancer progression has been emphasized in recent years. There are many ways to cause aneuploidy, however the genomic predispositions for these events are less well understood. In regards to the merotelic kinetochore attachments associated with... | Wikipedia - Anaphase lag - Genomic causes | 242 | 1,080 | null |
Section: Prognosis and treatment. Consequent of this genomic instability, the resulting cancer cells have the potential to diverge in sequence and gain new traits. This intratumoral heterogeneity creates a tumor mass with different genomic backgrounds as well as unique cellular traits and drug susceptibilities. Several... | Wikipedia - Anaphase lag - Prognosis and treatment | 289 | 1,422 | null |
Article: Aneuploidy. Aneuploidy is the presence of an abnormal number of chromosomes in a cell, for example a human somatic cell having 45 or 47 chromosomes instead of the usual 46. It does not include a difference of one or more complete sets of chromosomes. A cell with any number of complete chromosome sets is called... | Wikipedia - Aneuploidy - Summary | 314 | 1,357 | null |
Section: Chromosomes. Most cells in the human body have 23 pairs of chromosomes, or a total of 46 chromosomes. (The sperm and egg, or gametes, each have 23 unpaired chromosomes, and red blood cells in bone marrow have a nucleus at first but those red blood cells that are active in blood lose their nucleus and thus they... | Wikipedia - Aneuploidy - Chromosomes | 349 | 1,627 | null |
The most common aneuploidy that infants can survive with is trisomy 21, which is found in Down syndrome, affecting 1 in 800 births. Trisomy 18 (Edwards syndrome) affects 1 in 6,000 births, and trisomy 13 (Patau syndrome) affects 1 in 10,000 births. 10% of infants with trisomy 18 or 13 reach 1 year of age. Changes in ch... | Wikipedia - Aneuploidy - Chromosomes | 217 | 888 | null |
Section: Mechanisms. Aneuploidy arises from errors in chromosome segregation, which can go wrong in several ways. Nondisjunction usually occurs as the result of a weakened mitotic checkpoint, as these checkpoints tend to arrest or delay cell division until all components of the cell are ready to enter the next phase. F... | Wikipedia - Aneuploidy - Mechanisms | 327 | 1,559 | null |
Section: Somatic mosaicism in cancer. Aneuploidy is consistently observed in virtually all cancers. The German biologist Theodor Boveri was first to propose a causative role for aneuploidy in cancer. However, the theory of Boveri was forgotten until the molecular biologist Peter Duesberg reappraised it. Understanding t... | Wikipedia - Aneuploidy - Somatic mosaicism in cancer | 312 | 1,393 | null |
Loss of tumor suppressor p53 gene often results in genomic instability, which could lead to the aneuploidy genotype. In addition, genetic syndromes in which an individual is predisposed to breakage of chromosomes (chromosome instability syndromes) are frequently associated with increased risk for various types of cance... | Wikipedia - Aneuploidy - Somatic mosaicism in cancer | 329 | 1,602 | null |
Section: Partial aneuploidy. The terms "partial monosomy" and "partial trisomy" are used to describe an imbalance of genetic material caused by loss or gain of part of a chromosome. In particular, these terms would be used in the situation of an unbalanced translocation, where an individual carries a derivative chromos... | Wikipedia - Aneuploidy - Partial aneuploidy | 194 | 903 | null |
Section: Aneugens. Agents capable of causing aneuploidy are called aneugens. Many mutagenic carcinogens are aneugens. X-rays, for example, may cause aneuploidy by fragmenting the chromosome; it may also target the spindle apparatus. Other chemicals such as colchicine can also produce aneuploidy by affecting microtubule... | Wikipedia - Aneuploidy - Aneugens | 343 | 1,412 | null |
Section: Diagnosis. Germline aneuploidy is typically detected through karyotyping, a process in which a sample of cells is fixed and stained to create the typical light and dark chromosomal banding pattern and a picture of the chromosomes is analyzed. Other techniques include fluorescence in situ hybridization (FISH), ... | Wikipedia - Aneuploidy - Diagnosis | 222 | 1,010 | null |
Article: Annulate lamella. Annulate lamella is one of the cell membrane classes, occurring as a set of parallel elements with double-walled membranes in the same plane/dimension, just as the nuclear envelope. These lamella have pore complexes which are identical to those of the nuclear envelope. It is arranged in a hig... | Wikipedia - Annulate lamella - Summary | 195 | 952 | null |
Article: Autosome. An autosome is any chromosome that is not a sex chromosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosomal (sex chromosome) pairs, which may have different structures. The DNA in autosomes is collectively known as atDNA or auDNA. For example, hum... | Wikipedia - Autosome - Summary | 336 | 1,532 | null |
Section: Autosomal genetic disorders. Autosomal genetic disorders can arise due to a number of causes, some of the most common being nondisjunction in parental germ cells or Mendelian inheritance of deleterious alleles from parents. Autosomal genetic disorders which exhibit Mendelian inheritance can be inherited either... | Wikipedia - Autosome - Autosomal genetic disorders | 341 | 1,523 | null |
Possessing a single copy of an autosome (known as a monosomy) is nearly always incompatible with life, though very rarely some monosomies can survive past birth. Having three copies of an autosome (known as a trisomy) is far more compatible with life, however. A common example is Down syndrome, which is caused by posse... | Wikipedia - Autosome - Autosomal genetic disorders | 210 | 933 | null |
Section: Mechanism. The BFB cycle begins when the end region of a chromosome, called its telomere, breaks off. When that chromosome subsequently replicates it forms two sister chromatids which both lack a telomere. Since telomeres appear at the end of chromatids, and function to prevent their ends from fusing with othe... | Wikipedia - Breakage-fusion-bridge cycle - Mechanism | 258 | 1,152 | null |
Section: Detection. Breakage-fusion-bridge creates several identifiable cytogenetic abnormalities, such as anaphase bridges and dicentric chromosomes, which can be seen in progress using methods that have been available for decades. More recent methods, such as microarray hybridization and sequencing technologies, allo... | Wikipedia - Breakage-fusion-bridge cycle - Detection | 277 | 1,438 | null |
Section: Career. Chandley's work began at Christie Hospital with A.J. Bateman which established principles of sexual selection in gametes. Chandley also worked with Holt Radium Institute, and focussed on mutations and meiosis cell division, using cytogenetic methodology. These studies were on Drosophila and she complet... | Wikipedia - Ann Chester Chandley - Career | 344 | 1,681 | null |
Article: Chromoplexy. Chromoplexy refers to a class of complex DNA rearrangement observed in the genomes of cancer cells. This phenomenon was first identified in prostate cancer by whole genome sequencing of prostate tumors. Chromoplexy causes genetic material from one or more chromosomes to become scrambled as multipl... | Wikipedia - Chromoplexy - Summary | 324 | 1,444 | null |
Section: Proposed mechanism. The mechanism underlying complex rearrangements in chromoplexy has not been identified. A proposed model is that DNA is brought together in nuclear transcription hubs where genes across multiple chromosomes are co-regulated by transcription factors such as the Androgen receptor. This DNA ma... | Wikipedia - Chromoplexy - Proposed mechanism | 167 | 901 | null |
Section: Relation to chromothripsis. Chromoplexy is similar to, but distinct from chromothripsis, a phenomenon whereby a single catastrophic event causes “shattering” of a chromosome. The precise delineation between chromothripsis and chromoplexy is unclear, however general distinctions are Chromoplexy often involve se... | Wikipedia - Chromoplexy - Relation to chromothripsis | 278 | 1,212 | null |
Article: Chromosomal translocation. In genetics, chromosome translocation is a phenomenon that results in unusual rearrangement of chromosomes. This includes "balanced" and "unbalanced" translocation, with three main types: "reciprocal", "nonreciprocal" and "Robertsonian" translocation. Reciprocal translocation is a ch... | Wikipedia - Chromosomal translocation - Summary | 294 | 1,406 | null |
Section: History. Chromosomal translocations – in which a segment of one chromosome breaks off and attaches to another – were first observed in the early 20th century. In 1916, American zoologist William R. B. Robertson documented a chromosomal fusion in grasshoppers (now known as a Robertsonian translocation). In 1938... | Wikipedia - Chromosomal translocation - History | 315 | 1,594 | null |
Section: Balanced reciprocal translocations. Reciprocal translocations involve an exchange of material between non-homologous chromosomes. Such translocations are usually harmless, as they do not result in a gain or loss of genetic material, as is the case with nonreciprocal translocations. This type of translocation i... | Wikipedia - Chromosomal translocation - Balanced reciprocal translocations | 265 | 1,297 | null |
Section: Unbalanced reciprocal translocations. Unbalanced reciprocal translocations are similar to balanced reciprocal translocations in that they involve the exchange of genetic information between two non-homologous chromosomes. However, with unbalanced reciprocal translocations, the process results in the duplicatio... | Wikipedia - Chromosomal translocation - Unbalanced reciprocal translocations | 188 | 921 | null |
Section: Nonreciprocal translocation. Nonreciprocal translocation is a chromosomal abnormality that involves the one-way transfer of genes from one chromosome to another non-homologous chromosome. This transfer will always be unbalanced resulting in genetic imbalance. This excess or deletion of genetic material compare... | Wikipedia - Chromosomal translocation - Nonreciprocal translocation | 338 | 1,617 | null |
Section: Robertsonian translocations. Robertsonian translocation is a type of translocation caused by breaks at or near the centromeres of two acrocentric chromosomes. The reciprocal exchange of parts gives rise to one large metacentric chromosome and one extremely small chromosome that may be lost from the organism wi... | Wikipedia - Chromosomal translocation - Robertsonian translocations | 327 | 1,509 | null |
Section: Chromosomal Structural Changes. Changes in chromosome structure can be due to deletions, duplications and inversions, ultimately resulting in 3 main kinds of structural changes. Isochromosomes result when a chromosome has two identical arms, such as two P or two Q arms, instead of the expected Q and P pairing.... | Wikipedia - Chromosomal translocation - Chromosomal Structural Changes | 228 | 1,123 | null |
Section: DNA double-strand breaks with translocations. The initiating event in the formation of a translocation is generally a double-strand break in chromosomal DNA. Double stranded breaks in chromosomal DNA can occur for many reasons, however a major role in generating these translocations is the non-homologous end j... | Wikipedia - Chromosomal translocation - DNA double-strand breaks with translocations | 345 | 1,690 | null |
These sequences are the result of a deamination procedure of a cytosine nucleotide into a uracil nucleotide. This change ultimately results in a mismatch between the complementary sequence and its target sequence, therefore resulting in a translocation. When further processed by specific endonucleases, this uracil lead... | Wikipedia - Chromosomal translocation - DNA double-strand breaks with translocations | 326 | 1,568 | null |
Section: Role in Disease. Chromosomal translocations can cause a diverse array of diseases, mutations or other heritable changes within an individuals genomes. Often, these mutations are caused by the loss of genetic information resulting from a structural change in the chromosome. There are three main forms of structu... | Wikipedia - Chromosomal translocation - Role in Disease | 346 | 1,758 | null |
Infertility is also a prevalent and common form of disease that is generated by chromosomal translocations, and often can be asymptomatic or symptomatic within fetuses. Commonly influenced by one of the parents being a carrier for a balanced translocation yet being asymptomatic, the offspring often acquire additional m... | Wikipedia - Chromosomal translocation - Role in Disease | 331 | 1,573 | null |
Section: By chromosome > Denotation. The International System for Human Cytogenetic Nomenclature (ISCN) is used to denote a translocation between chromosomes. The designation "t(A;B)(p1;q2)" is used to denote a translocation between chromosome A and chromosome B. The information in the second set of parentheses, when g... | Wikipedia - Chromosomal translocation - By chromosome > Denotation | 168 | 756 | null |
Article: Chromosome. A chromosome is a package of DNA containing part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells, the most important of these proteins are the histones. Aided by chaperone pr... | Wikipedia - Chromosome - Summary | 349 | 1,751 | null |
Section: History of discovery. Otto Bütschli was the first scientist to recognize the structures now known as chromosomes. In a series of experiments beginning in the mid-1880s, Theodor Boveri gave definitive contributions to elucidating that chromosomes are the vectors of heredity, with two notions that became known a... | Wikipedia - Chromosome - History of discovery | 339 | 1,653 | null |
Section: Prokaryotes. The prokaryotes – bacteria and archaea – typically have a single circular chromosome. The chromosomes of most bacteria (also called genophores), can range in size from only 130,000 base pairs in the endosymbiotic bacteria Candidatus Hodgkinia cicadicola and Candidatus Tremblaya princeps, to more t... | Wikipedia - Chromosome - Prokaryotes | 170 | 695 | null |
Section: Prokaryotes > DNA packaging. Prokaryotes do not possess nuclei. Instead, their DNA is organized into a structure called the nucleoid. The nucleoid is a distinct structure and occupies a defined region of the bacterial cell. This structure is, however, dynamic and is maintained and remodeled by the actions of a... | Wikipedia - Chromosome - Prokaryotes > DNA packaging | 302 | 1,364 | null |
Section: Eukaryotes. Each eukaryotic chromosome consists of a long linear DNA molecule associated with proteins, forming a compact complex of proteins and DNA called chromatin. Chromatin contains the vast majority of the DNA in an organism, but a small amount inherited maternally can be found in the mitochondria. It is... | Wikipedia - Chromosome - Eukaryotes | 252 | 1,183 | null |
Section: Eukaryotes > Interphase chromatin. The packaging of DNA into nucleosomes causes a 10 nanometer fibre which may further condense up to 30 nm fibres. Most of the euchromatin in interphase nuclei appears to be in the form of 30-nm fibers. Chromatin structure is the more decondensed state, i.e. the 10-nm conformat... | Wikipedia - Chromosome - Eukaryotes > Interphase chromatin | 224 | 936 | null |
Section: Eukaryotes > Metaphase chromatin and division. In the early stages of mitosis or meiosis (cell division), the chromatin double helix becomes more and more condensed. They cease to function as accessible genetic material (transcription stops) and become a compact transportable form. The loops of thirty-nanomete... | Wikipedia - Chromosome - Eukaryotes > Metaphase chromatin and division | 346 | 1,630 | null |
During mitosis, microtubules grow from centrosomes located at opposite ends of the cell and also attach to the centromere at specialized structures called kinetochores, one of which is present on each sister chromatid. A special DNA base sequence in the region of the kinetochores provides, along with special proteins, ... | Wikipedia - Chromosome - Eukaryotes > Metaphase chromatin and division | 158 | 740 | null |
Section: Eukaryotes > Human chromosomes. Chromosomes in humans can be divided into two types: autosomes (body chromosome(s)) and allosome (sex chromosome(s)). Certain genetic traits are linked to a person's sex and are passed on through the sex chromosomes. The autosomes contain the rest of the genetic hereditary infor... | Wikipedia - Chromosome - Eukaryotes > Human chromosomes | 264 | 1,255 | null |
Section: Karyotype. In general, the karyotype is the characteristic chromosome complement of a eukaryote species. The preparation and study of karyotypes is part of cytogenetics. Although the replication and transcription of DNA is highly standardized in eukaryotes, the same cannot be said for their karyotypes, which a... | Wikipedia - Chromosome - Karyotype | 313 | 1,410 | null |
Section: Karyotype > History and analysis techniques. Investigation into the human karyotype took many years to settle the most basic question: How many chromosomes does a normal diploid human cell contain? In 1912, Hans von Winiwarter reported 47 chromosomes in spermatogonia and 48 in oogonia, concluding an XX/XO sex ... | Wikipedia - Chromosome - Karyotype > History and analysis techniques | 281 | 1,290 | null |
Section: Aberrations. Chromosomal aberrations are disruptions in the normal chromosomal content of a cell. They can cause genetic conditions in humans, such as Down syndrome, although most aberrations have little to no effect. Some chromosome abnormalities do not cause disease in carriers, such as translocations, or ch... | Wikipedia - Chromosome - Aberrations | 331 | 1,529 | null |
Down syndrome, the most common trisomy, usually caused by an extra copy of chromosome 21 (trisomy 21). Characteristics include decreased muscle tone, stockier build, asymmetrical skull, slanting eyes, and mild to moderate developmental disability. Edwards syndrome, or trisomy-18, the second most common trisomy. Symptom... | Wikipedia - Chromosome - Aberrations | 337 | 1,555 | null |
This means there is an extra, abnormal chromosome. Features depend on the origin of the extra genetic material. Cat-eye syndrome and isodicentric chromosome 15 syndrome (or Idic15) are both caused by a supernumerary marker chromosome, as is Pallister–Killian syndrome. Triple-X syndrome (XXX). XXX girls tend to be tall ... | Wikipedia - Chromosome - Aberrations | 235 | 1,035 | null |
Section: Number in various organisms > In eukaryotes. The number of chromosomes in eukaryotes is highly variable. It is possible for chromosomes to fuse or break and thus evolve into novel karyotypes. Chromosomes can also be fused artificially. For example, when the 16 chromosomes of yeast were fused into one giant chr... | Wikipedia - Chromosome - Number in various organisms > In eukaryotes | 350 | 1,593 | null |
Gametes (reproductive cells) are haploid [n], having one set of chromosomes. Gametes are produced by meiosis of a diploid germline cell, during which the matching chromosomes of father and mother can exchange small parts of themselves (crossover) and thus create new chromosomes that are not inherited solely from either... | Wikipedia - Chromosome - Number in various organisms > In eukaryotes | 206 | 908 | null |
Section: Number in various organisms > In prokaryotes. Prokaryote species generally have one copy of each major chromosome, but most cells can easily survive with multiple copies. For example, Buchnera, a symbiont of aphids, has multiple copies of its chromosome, ranging from 10 to 400 copies per cell. However, in some... | Wikipedia - Chromosome - Number in various organisms > In prokaryotes | 161 | 667 | null |
Article: Chromosome abnormality. A chromosomal abnormality, chromosomal anomaly, chromosomal aberration, chromosomal mutation, or chromosomal disorder is a missing, extra, or irregular portion of chromosomal DNA. These can occur in the form of numerical abnormalities, where there is an atypical number of chromosomes, o... | Wikipedia - Chromosome abnormality - Summary | 227 | 1,143 | null |
Section: Numerical abnormality. Maintaining a euploid state, where cells contain the correct number of chromosome sets, is essential for genomic stability. Aneuploidy, characterized by an abnormal number of chromosomes, occurs when an individual is missing a chromosome from a pair (monosomy) or has an additional chromo... | Wikipedia - Chromosome abnormality - Numerical abnormality | 320 | 1,404 | null |
Section: Structural abnormalities. Structural abnormalities in chromosomes may result from breakage and improper realignment of chromosome segments. When the structure of a chromosome is altered, it can result in unbalanced rearrangements, balanced rearrangements, ring chromosomes, and isochromosomes. To expand, these ... | Wikipedia - Chromosome abnormality - Structural abnormalities | 327 | 1,624 | null |
There are two main types of translocations: Reciprocal translocation: Segments from two different chromosomes have been exchanged. Robertsonian translocation: A pair of chromosomes break at their centromeres, lose their short p arms, and fuse at their q arms, forming a single chromosome with one centromere. This type o... | Wikipedia - Chromosome abnormality - Structural abnormalities | 195 | 942 | null |
Section: Inheritance. Constitutional chromosome abnormalities (present at beginning of development) arise during gametogenesis or embryogenesis, affecting a significant proportion of an organism’s cells. These inherited abnormalities most commonly occur as errors in the egg or sperm, meaning the anomaly is present in e... | Wikipedia - Chromosome abnormality - Inheritance | 345 | 1,777 | null |
X-linked dominant diseases can affect both males and females. A father with an X-linked dominant trait may only pass it to his daughters, while a mother can pass the trait to both sons and daughters. An example of this is incontinentia pigmenti. Mitochondrial inheritance: This pattern affects both males and females but... | Wikipedia - Chromosome abnormality - Inheritance | 342 | 1,705 | null |
Section: Acquired chromosome abnormalities. Acquired chromosomal abnormalities represent genetic alterations that manifest during an individual's lifetime, as opposed to being inherited from their parents. These modifications predominantly occur within somatic cells and are characterized by their non-heritable nature. ... | Wikipedia - Chromosome abnormality - Acquired chromosome abnormalities | 325 | 1,825 | null |
Mutagens can be classified as physical, chemical, or biological: Chemical: Common chemical mutagens include base analogs (molecules that resemble nitrogenous bases), deaminating agents (which remove amino groups), alkylating agents, and intercalating agents. Physical: The most prevalent sources of physical mutagens are... | Wikipedia - Chromosome abnormality - Acquired chromosome abnormalities | 336 | 1,593 | null |
Most cancers, if not all, could cause chromosome abnormalities, with either the formation of hybrid genes and fusion proteins, deregulation of genes and overexpression of proteins, or loss of tumor suppressor genes (see the "Mitelman Database" and the Atlas of Genetics and Cytogenetics in Oncology and Haematology,). Ap... | Wikipedia - Chromosome abnormality - Acquired chromosome abnormalities | 163 | 771 | null |
Section: DNA damage during spermatogenesis. DNA damage during spermatogenesis plays a crucial role in chromosomal abnormalities and male fertility. In the early stages of sperm development, DNA repair mechanisms such as homologous recombination (HR) and mismatch repair (MMR) efficiently correct replication errors and d... | Wikipedia - Chromosome abnormality - DNA damage during spermatogenesis | 326 | 1,510 | null |
Normally, defective sperm cells are removed through apoptosis, a controlled cell death process. However, if this system fails—such as when there is an imbalance between pro-apoptotic (BAX) and anti-apoptotic (BCL-2) factors—damaged sperm may survive. If these sperm fertilize an egg, the oocyte's repair mechanisms may a... | Wikipedia - Chromosome abnormality - DNA damage during spermatogenesis | 263 | 1,223 | null |
Section: Detection. Chromosomal abnormalities can be detected at either postnatal testing or prenatal screening, which includes prenatal diagnosis. Early detection is crucial for enabling parents to assess their upcoming pregnancy options. Common techniques used to detect diseases resulting from chromosomal abnormaliti... | Wikipedia - Chromosome abnormality - Detection | 340 | 1,709 | null |
FISH is a technique used for the treatment of specific cases such as Multiple myeloma (MM) and can be used to analyze bone marrow samples to identify changes in chromosomes at a single-cell level. For the treatment of MM relapse, acquired chromosomal abnormalities such as del (17p), amp (1q) and Tetraploidy can be anal... | Wikipedia - Chromosome abnormality - Detection | 253 | 1,172 | null |
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