BIO - TERMS - CHROMOSOME Flashcards
Acentric chromosome
Chromosome fragment lacking a centromere.
Acrocentric
A modifying term for a chromosome or chromatid that has its centromere near the end.
Amniocentesis
A procedure for obtaining amniotic fl uid from a pregnant woman. Chemical contents of the fl uid are studied directly for the diagnosis of some diseases. Cells are cultured, and metaphase chromosomes are examined for irregularities (for example, trisomy).
Amphidiploid
A species or type of plant derived from doubling the chromosomes in the F1 hybrid of two species; an allopolyploid. In an amphidiploid the two species are known, whereas in other allopolyploids they may not be known.
anaphase A
Stage of mitosis during which chromosome segregation occurs as chromosomes move toward the two spindle poles.
anaphase B
Stage of mitosis during which chromosome segregation occurs as spindle poles separate and move apart. anaphase-promoting complex (APC/C; cyclosome) Ubiquitin ligase that catalyzes the ubiquitylation and destruction of securin and M- and S-cyclins, initiating the separation of sister chromatids in the metaphase-to-anaphase transition during mitosis.
Anaphase I
The stage during the first meiotic division when duplicated homologous chromosomes separate from each other and begin moving to opposite poles of the cell.
Anaphase II
The stage during the second meiotic division when sister chromatids of a duplicated chromosome separate from each other and begin moving to opposite poles of the cell.
Aneuploidy
Deficiency or excess of a chromosome.
astral microtubule
In the mitotic spindle, any of the microtubules radiating from the aster which are not attached to a kinetochore of a chromosome.
Asynapsis
The failure or partial failure in the pairing of homologous chromosomes during the meiotic prophase.
Barr body
A condensed mass of chromatin found in the nuclei of placental mammals that contains one or more X chromosomes; named for its discoverer, Murray Barr.
Chromocenter
Body produced by fusion of the heterochromatic regions of the chromosomes in the polytene tissues (for example, the salivary glands) of certain Diptera.
Chromomeres
Small bodies that are identified by their characteristic size and linear arrangement along a chromosome.
Chromonema (pl, chromonemata)
An optically single thread forming an axial structure within each chromosome.
Chromosome aberration
Abnormal structure or number of chromosomes; includes deficiency, duplication, inversion, translocation, aneuploidy, polyploidy, or any other change from the normal pattern.
Chromosome banding
Staining of chromosomes in such a way that light and dark areas occur along the length of the chromosomes. Lateral comparisons identify pairs. Each human chromosome can be identified by its banding pattern.
Chromosome walking
A procedure that uses overlapping clones to move sequentially down a chromosome from one site to another site. (See also Positional cloning.)
ClB chromosome
An X chromosome in Drosophila that carries a mutation causing bar-shaped eyes and a recessive lethal mutation within a large inversion.
ClB method
The use of a special X chromosome in Drosophila that carries a mutation causing bar-shaped eyes and a recessive lethal mutation within a long inversion to detect new recessive X-linked lethal mutations. H. J. Muller used this chromosome to demonstrate that X rays are mutagenic. See also ClB chromosome.
Coefficient of coincidence
The ratio of the observed frequency of double crossovers to the expected frequency, which is calculated on the assumption that crossovers in adjacent segments of the chromosome occur independently.
Compound chromosome
A chromosome formed by the union of two separate chromosomes from the same pair, as in attached-X chromosomes or attached X-Y chromosomes.
Cosmids
Cloning vectors that are hybrids between phage λ chromosomes and plasmids; they contain λ cos sites and plasmid origins of replication.
Cri-du-chat syndrome
A condition produced when a small region in the short arm of one human chromosome 5 is deleted.
Cytological map
A diagram of a chromosome based on differential staining—the “banding pattern”—along its length.
Deficiency (deletion)
Absence of a segment of a chromosome, reducing the number of loci.
Dicentric chromosome
One chromosome having two centromeres.
Diplonema (adj, diplotene)
That stage in prophase of meiosis I following the pachytene stage, but preceding diakinesis, in which the chromosomes of bivalents separate from each other at and around their centromeres.
Disjunction
Separation of homologous chromosomes during anaphase of mitotic or meiotic divisions. (See also Nondisjunction.)
Down syndrome
The phenotype due to the presence of an extra chromosome 21 in humans.
Endomitosis
Duplication of chromosomes without division of the nucleus, resulting in increased chromosome number within a cell. Chromosome strands separate, but the cell does not divide.
Endopolyploidy
A state in which the cells of a diploid organism contain multiples of the diploid chromosome number (that is, 4n, 8n, and so on).