chromosome (redirected from Chromosome theory of inheritance)

chromosome /chro·mo·some/ (kro´mah-sōm) in animal cells, a structure in the nucleus containing a linear thread of DNA which transmits genetic information and is associated with RNA and histones; 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 the two (XX or XY) which determine the sex of the organism. In bacterial genetics, a closed circle of double-stranded DNA which contains the genetic material of the cell and is attached to the cell membrane; the bulk of this material forms a compact bacterial nucleus.chromoso´mal

Chromosome. (A), Long, threadlike interphase chromatin in nucleus. (B), Giemsa-stained, partially condensed chromatid in late prophase. (C), Giemsa-stained, fully condensed chromatid in metaphase; note that some of the sub-bands visible in late prophase have condensed into single bands. (In B and C, only one of a pair of sister chromatids is shown.)

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bivalent chromosome  see bivalent (2).

homologous chromosomes  a matching pair of chromosomes, one from each parent, with the same gene loci in the same order.

Ph1 chromosome , Philadelphia chromosome an abnormality of chromosome 22, characterized by shortening of its long arms (the missing portion probably translocated to chromosome 9); present in marrow cells of patients with chronic granulocytic 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 chromosomes  those associated with sex determination, in mammals constituting an unequal pair, the X and the Y chromosome.

somatic chromosome  autosome.

X chromosome  a sex chromosome, carried by half the male gametes and all female gametes; female diploid cells have two X chromosomes.

Y chromosome  a sex chromosome, carried by half the male gametes and none of the female gametes; male diploid cells have an X and a Y chromosome.

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chro·mo·some (krm-sm)

n.

1. A threadlike linear strand of DNA and associated proteins in the nucleus of animal and plant cells that carries the genes and functions in the transmission of hereditary information.

2. A circular strand of DNA in bacteria and cyanobacteria that contains the hereditary information necessary for cell life.

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chromo·somal (-sml), chromo·somic (-smk) adj.

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Chromosome

A structure composed of deoxyribonucleic acid (DNA) contained within a cell's nucleus (center) where genetic information is stored. Human have 23 pairs of chromosomes, each of which has recognizable characteristics (such as length and staining patterns) that allow individual chromosomes to be identified. Identification is assigned by number (1-22) or letter (X or Y).

Mentioned in: Acoustic Neuroma, Amniocentesis, Birth Defects, Cerebral Amyloid Angiopathy, Cri Du Chat Syndrome, Down Syndrome, Edwards' Syndrome, Fragile X Syndrome, Gene Therapy, Genetic Testing, Hereditary Hemorrhagic Telangiectasia, Huntington Disease, Klinefelter Syndrome, Neurofibromatosis, Patau Syndrome, Retinoblastoma, Turner Syndrome, Von Willebrand Disease, Wilson Disease

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chromosome

[krō′məsōm]

Etymology: Gk, chroma + soma, body

any of the threadlike structures in the nucleus of a cell that function in the transmission of genetic information. Each consists of a double strand of DNA attached to proteins called histones. The genes, which contain the genetic material that controls the inheritance of traits, are arranged in a linear pattern along the length of each DNA strand. Chromosomes are readily stainable with basic dyes and can be seen easily during cell division, when they are compactly coiled and in their most condensed state. During interphase the chromosomes disperse into chromatin and undergo self-replication, forming identical chromatids that separate during mitosis so that each new cell receives a full set of chromosomes. Each species has a characteristic number of chromosomes in each somatic cell. In humans, there are 46 chromosomes, including 22 homologous pairs of autosomes and 1 pair of sex chromosomes. One member of each pair is derived from each parent. Kinds of chromosomes include Christchurch chromosomes, daughter chromosomes, gametic chromosomes, giant chromosomes, homologous chromosomes, monosomes, Philadelphia chromosomes, sex chromosomes, somatic chromosomes, and W chromosomes. See also centromere, chromatid, chromatin, Denver classification, gene, karyotype, mitosis. chromosomal, adj.

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chromosome

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.

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. The diploid numbers (number of total chromosomes per cell) are cattle—60, sheep—54, horse—64, donkey—62, pig—38, dog—78, cat—38, human—46. The chromosomes are arranged in pairs and one of the pairs is the sex chromosomes (XX or XY), which determines the sex of the organism. See also heredity.

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compound chromosome

a genetic engineering procedure which produces two chromosomes in one of which the left arms of the two original chromosomes are joined together and the two original right arms are also joined together; used in genetic control of insect populations.

homologous c's

the chromosomes of a matching pair in the diploid complement that contain alleles of specific genes.

lampbrush chromosome

so named because of the bristling appearance given them by many open loops of chromatin along the extended chromosome.

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 constituting an unequal pair, the X and the Y chromosome.

somatic chromosome

autosome.

submetacentric chromosome

see submetacentric.

W chromosome

sex chromosome in animals such as poultry in which the female is the heterogametic state, the male has the ZZ genotype and the female the ZW genotype.

X chromosome

the female sex chromosome, being carried by half the male gametes and all female gametes; female diploid cells have two X chromosomes, the male has the XY genotype.

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; females carry the XX genotype.

Z chromosome

sex chromosome in animals, such as poultry, in which the female is the heterogametic sex; the male has the ZZ genotype and the female the ZW genotype.

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chromosome 

One of the thread-like structures located within the cell nucleus composed of an extremely long, double-stranded DNA (deoxyribonucleic acid) helix tightly folded around proteins called histones. Each chromosome carries genes that contain the hereditary material that controls the growth and characteristics of the body. There are 46 chromosomes in each human somatic cell organized in 23 pairs, of which 22 pairs are similar in appearance but differ at the molecular level. They are called autosomal chromosomes or autosomes and are designated by a number (with chromosome 1 being the longest, followed by chromosome 2, etc.). The other pair, the sex chromosomes determines the sex of the individual. In mammals the two sex chromosomes of females are alike (homologous) and are referred to as X chromosomes. Males carry one X chromosome along with a much shorter chromosome, the Y chromosome. Each chromosome has a centromere that divides it into two arms, the short arm 'p' and the long arm 'q'. Disorders of chromosome number in which the number of chromosomes is above or below the normal (46) are called aneuploidy. Common forms of aneuploidy are trisomy in which there is one extra chromosome and monosomy in which there is one less, than the normal 46. They rarely cause specific eye diseases but affected individuals present ocular manifestations. Examples: Down's syndrome (trisomy of chromosome 21), Edwards' syndrome (trisomy 18), Turner's syndrome (monosomy 45 XO). There are other chromosome abnormalities such as translocation (one segment of a chromosome is transferred to another chromosome) as may occur in congenital anterior polar cataract, deletion (a loss of a piece of chromosome) as in aniridia, choroideremia, retinoblastoma, etc. Other cases involve damage of a chromosome (e.g. fragile X syndrome). See defective colour vision; gene; mitosis; mutation.

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chromosome

Genetics adjective Etymologically incorrect, but widely preferred noun Any of a number of paired units of the self-replicating genetic material in the eukaryotic nucleus, the 'master genetic database' containing the complete information present in a cell or virus which results in the palette of phenotypic expression of the individual; human chromosomes consist of 23 long–100-300 million bp, each–paired DNA or, in some organisms, RNA molecules that in humans are associated with RNA and histone proteins, and most readily recognized during mitosis as they align themselves on the metaphase plate; chromosomes are divided into structurally similar groups based on length from the centromere: group A–chromosomes 1-3; B–chromosomes 4, 5; C–chromosomes 6–12, X chromosome; D–chromosomes 13–15; E–chromosomes 16–18; F–chromosomes 19, 20; G–chromosomes 21, 22, Y chromosome. See Acentric chromosome, Accessory chromosome, Autosomal chromosome, B chromosome, Bacterial artificial chromosome, C banding, Christchurch chromosome, Eukaryote, Flow cytometry, G banding, Gene, Harlequin chromosome, Honorary chromosome, Homologous chromosome, Human genome project, Isochromosome, Lampbrush chromosome, Marker chromosome, Minichromosome chromosome, Nucleotide, Philadelphia chromosome, Ploidy analysis, Polytene chromosome, Protein, Q Banding, Ring chromosome, Sex chromosome, Translation, Transcription.,Unbanded chromosome, X chromosome, Y chromosome.