The Chromosomal Basis Of Inheritance

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aneuploidy

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A chromosomal aberration in which certain chromosomes are present in extra copies or are deficient in number

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Barr body

Back 2

A dense object lying along the inside of the nuclear envelope in female mammalian cells, representing an inactivated X chromosome

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deletion

Back 3

(1) A deficiency in a chromosome resulting from the loss of a fragment through breakage (2) A mutational loss of one or more nucleotide pairs from a gene

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genetic map

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An ordered list of genetic loci (genes or other genetic markers) along a chromosome

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genetic recombination

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The general term for the production of offspring with new combinations of traits inherited from the two parents

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inversion

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An aberration in chromosome structure resulting from an error in meiosis or from mutagens; specifically, reattachment of a chromosomal fragment to the chromosome from which the fragment originated, but in a reverse orientation

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linkage map

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A genetic map based on the frequencies of recombination between markers during crossing over of homologous chromosomes; the greater the frequency of recombination between two genetic markers, the farther apart they are assumed to be

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map units

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A measurement of the distance between genes

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monosomic

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A chromosomal condition in which a particular cell has only one copy of a chromosome, instead of the normal two

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mosaic

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A pattern of development in which an organism consists of two sets of cells that differ according to which X chromosome is inactivated

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nondisjunction

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An accident of meiosis or mitosis, in which the members of a pair of homologous chromosomes or sister chromatids fail to move apart properly

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polyploidy

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A chromosomal alteration in which the organism possesses more than two complete chromosome sets

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recombinant

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An offspring whose phenotype differs from that of the parents

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sex-linked gene

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A gene located on a sex chromosome

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translocation

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(1) An aberration in chromosome structure resulting from an error in meiosis or from mutagens; specifically, attachment of a chromosomal fragment to a nonhomologous chromosome. (2) During protein synthesis, the third stage in the elongation cycle when the RNA carrying the growing polypeptide moves from the A site to the P site on the ribosome. (3) The transport via phloem of food in a plant.

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trisomic

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A chromosomal condition in which a particular cell has an extra copy of one chromosome, instead of the normal two

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wild type

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An individual with the normal phenotype

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duplication

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An aberration in chromosome structure resulting from an error in meiosis or mutagens; duplication of a portion of a chromosome resulting from fusion with a fragment from a homologous chromosome