Barr body
... sex is determined by the presence of the Y or W
chromosome rather than the diploidy of the X or Z, a Barr body is the inactive X
chromosome in a female cell, or the inactive Z in a male. ... some placental mammals, in which the father's X
chromosome is always deactivated.
The inactivation state ...
Cell growth
... , a process that includes DNA replication,
chromosome segregation, and cytokinesis. Eukaryotic cell ... . There are two distinct sex chromosomes, the X
chromosome and the Y chromosome. A diploid human cell has 23 ... That is, your body has two copies of human
chromosome number 2, one from each of your parents.
...
Centromere
... The centromere is a region of a eukaryotic
chromosome where the kinetochore is assembled. Thus, it ... fibers of the mitotic spindle attach to the
chromosome during mitosis . It is also the site of the ... (dicentric chromosomes) will result in
chromosome breakage during mitosis.
The centromeric DNA is ...
Chromatin
... Chromatin is the substance of a
chromosome and consists of a complex of DNA and protein ... on a string"
30 nm condensed chromatin fiber
chromosome
Sperm chromatin is an exception to the ... copies of the DNA molecule are now present) (5)
chromosome during metaphase .
Two distinct types of ...
Chromatid
... A chromatid forms one part of a
chromosome after it has coalesced for the process of mitosis or meiosis . Each
chromosome consists of two exactly identical (" sister ") ... 46 chromosomes. When it is ready to divide, each
chromosome will replicate itself during the Synthesis phase ...
Chromosome
... about chromosomes in genetic algorithms , see
chromosome (genetic algorithm) .
Figure 1: ... Chromatid . One of the two identical parts of the
chromosome after S phase . (2) Centromere . The point ... attach. (3) Short arm. (4) Long arm.
A
chromosome (in Greek chroma = colour and soma = body) ...
Chromosome walking
...
chromosome walking is a method in genetics for ... long parts of a DNA strand, e.g., a
chromosome . As the traditional chain termination method ... be used to sequence entire chromosomes (thus,
chromosome walking ). A different method with the same ...
Chromosomal crossover
... the result can be a duplication of genes on one
chromosome and a deletion of these on the other. If they ... sides of the centromere , the result can be one
chromosome being lost during cell division . If homologous
chromosome are not perfectly aligned an unequal crossover ...
Ploidy
... in Greek ) cells bear one copy of each
chromosome .
Most fungi , and a few algae exist as ... in Greek ) have two copies ( homologs ) of each
chromosome (both sex- and non-sex determining chromosomes), ... that forces a normal cell to spit out half of its
chromosome content, leaving just one set. In mammals this ...
Down syndrome
... 21 is the existence of the third copy of the
chromosome 21 in cells throughout the body of the affected ... of genes (e.g., various translocations of
chromosome 21). Depending on the actual etiology , the ... results in over- expression of genes located on
chromosome 21. One of these is the superoxide dismutase ...
Edward's syndrome
... Syndrome occurs when three sets (trisomy) of
chromosome 18 occur.
Trisomy 18 is therefore caused by ... pairs of chromosomes needed to form a healthy, 46
chromosome cell. However, sometimes egg and sperm cells are ... some of the body's cells have an extra copy of
chromosome 18, resulting in a mixed population of cells with ...
Gamete
... of an individual will contain one copy of the
chromosome set from the sperm and one copy of the
chromosome set from the egg—that is, the cells of the ... This recombination, and the fact that the two
chromosome sets ultimately have come from either a ...
Gene
... The location (or locus ) of a gene and the
chromosome on which it is situated is in a sense arbitrary. ... mice. Two genes positioned near one another on a
chromosome may encode proteins that figure in the same ... in spermatogenesis reside together on the Y
chromosome .
Many species carry more than one copy of ...
Ploidy
... in Greek ) cells bear one copy of each
chromosome .
Most fungi , and a few algae exist as ... in Greek ) have two copies ( homologs ) of each
chromosome (both sex- and non-sex determining chromosomes), ... that forces a normal cell to spit out half of its
chromosome content, leaving just one set. In mammals this ...
Human
... the sex chromosomes XX and males have XY. The X
chromosome is longer and carries many genes not on the Y ... Women have a blood-clotting gene on each X
chromosome so that one normal blood-clotting gene can ... gene since there is no gene on the Y
chromosome to control blood clotting. As a result, men will ...
Human Genome Project
... Genome Project, titled Human Genome Project,
chromosome Number # (# denotes 01-22, X and Y). This ... through http://www.gutenberg.org/etext/3501 for
chromosome 1 sequentially to ... revisions and refinements. In addition to the
chromosome files, there is a supplementary information file ...
Karyotype
... 45,Y, does not occur, as an embryo without an X
chromosome is incapable of survival.
Contents ... This is also referred to as G-banding . Each
chromosome has a characteristic banding patern which helps ... several different probes specific of one
chromosome pair, carrying different amounts of a set of ...
Klinefelter's syndrome
... syndrome is a condition caused by a
chromosome abnormality in males (specifically, a ... males usually have an XY karyotype . The XXY
chromosome arrangement is one of the most common genetic ... symptoms that may result from having the extra
chromosome are less common. Because of this extra ...
Lyon hypothesis
... bodies is called Lyonization .
In humans the X
chromosome that is inactivated is determined by chance. In marsupials , however, the paternal X
chromosome is always inactivated. Inactivation is achieved by methylation of the X
chromosome DNA, a common way in which the cell silences ...
Meiosis
... structure appears as a pair of chromatids. Each
chromosome becomes two chromatids. The chromosomes join at ... sets of chromosomes form at opposing poles. Each
chromosome consists of a sister chromatid pair, as ... now has half the number of chromosomes but each
chromosome consists of a pair of chromatids. Telophase I ...
Mitosis
...
In biology , mitosis is the process of
chromosome segregation and nuclear division that follows ... lack a nucleus and only have a single
chromosome with no centromere, they cannot be properly said ... into a highly ordered structure called a
chromosome . Since the genetic material has been ...
Nondisjunction
... biology , nondisjunction is the failure of a
chromosome to split correctly during meiosis .
This ... including:
Down Syndrome - trisomy of
chromosome 21
Patau Syndrome - trisomy of
chromosome 13
Edward Syndrome - trisomy ...
Patau syndrome
... a disease in which a patient has an additional
chromosome 13 .
Patau syndrome is associated with severe ... with Patau syndrome have additional DNA from
chromosome 13 in some or all of their cells. The extra ... means each cell in the body has three copies of
chromosome 13 instead of the usual two copies. A small ...
Prophase
... into a highly ordered structure called a
chromosome . Since the genetic material has been duplicated, there are two identical copies of each
chromosome in the cell. Identical chromosomes (called sister ... to each other at a DNA element present on every
chromosome called the centromere .
When chromosomes are ...
Mitosis
...
In biology , mitosis is the process of
chromosome segregation and nuclear division that follows ... lack a nucleus and only have a single
chromosome with no centromere, they cannot be properly said ... into a highly ordered structure called a
chromosome . Since the genetic material has been ...
Twin
... during the twinning process, one twin loses a Y
chromosome (boys have
chromosome type XY while girls have XX). Without a Y
chromosome to trigger the production of male sex hormones , ...
X chromosome
... The X
chromosome is one of the two sex chromosomes in humans and other animals (the other is the Y
chromosome ). It is a part of the XY sex-determination ... one of the 23 pairs of human chromosomes. The X
chromosome spans more than 153 million base pairs (the ...
Y chromosome
... The Y
chromosome is one of the two sex chromosomes in humans (the other is the X
chromosome ). The sex chromosomes are one of the 23 pairs of human chromosomes. The Y
chromosome spans about 50 million base pairs (the building ...
Anaphase
... yeast and certain protozoa use anaphase B as the main means of
chromosome separation and can extend the spindle to up to 15 times its metaphase ... cytokinesis
prophase
prometaphase
metaphase
telephase
chromosome
prokaryote
eukaryote
...
Autosome
...
An autosome is a non-sex
chromosome . It is an ordinary paired
chromosome that is the same in both sexes of a species . For example, in humans, ...
Bacterial conjugation
... is an episome (a plasmid that can integrate itself into the bacterial
chromosome by genetic recombination ) of about 100 kb (kilo base pairs ) length. ... on how long the bacteria hold contact; the transfer of the whole bacterial
chromosome would take about 100 minutes. The transferred DNA can be integrated into ...
Morphogenesis
... selector genes . These genes exist in two ordered groups on Drosophila
chromosome 3. The order of the genes on the
chromosome reflects the order that they are expressed along the anterior-posterior ...
Gene therapy
... way of bypassing the DNA problems by actually introducing an extra
chromosome into the body. Existing alongside existing DNA, this 47th
chromosome would contain the genes needed. Introduced into the body as a large ...
Genetics
... Crick
1956 Jo Hin Tjio and Albert Levan established the correct
chromosome number in humans to be 46
1958 The Meselson-Stahl experiment ... are known as quantitative traits, and their mapping to a location on the
chromosome requires accurate phenotypic, pedigree and marker data from a large ...
Morphogenesis
... selector genes . These genes exist in two ordered groups on Drosophila
chromosome 3. The order of the genes on the
chromosome reflects the order that they are expressed along the anterior-posterior ...
Prokaryote
... circular (only exceptionally linear, as in Borrelia burgdorferi )
chromosome , contained within a region called nucleoid , rather than in a ... Reproduction is exclusively asexual , through binary fission , where the
chromosome is duplicated and attaches to the cell membrane, and then the cell divides ...
Thomas Hunt Morgan
... traits were sex-linked , (2) the trait was probably carried on the sex
chromosome (ie the X and Y chromosomes), and (3) other genes were probably carried ... of thousands of fruit flies and studied their inheritance. Using
chromosome recombination, Morgan and Alfred Sturtevant formed a map of genes' ...
Allele
... An allele is any one of a number of alternative forms of the same gene occupying a given locus (position) on a
chromosome . An example is the gene for blossom color in many species of flower - a single gene controls the color of the petals, but there may be several ...
Allele frequency
... of a species population , or equivalently the richness of its gene pool . Allele frequency is defined as follows:
Given a) a particular
chromosome locus , b) a gene occupying that locus, c) a population of individuals carrying n loci in each of their somatic cells (e.g. two loci in the ...
Cancer
... mutation, whereas tumor suppressor genes prevent cancer unless "switched off" by a mutation. Chromosomal translocation , such as the Philadelphia
chromosome , is a special type of mutation and may involve oncogenes or tumor suppressor genes. In general, mutations in both types of genes are necessary, as a ...