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).
Equatorial plate
The figure formed by the chromosomes in the center (equatorial plane) of the spindle in mitosis.
Euploid
An organism or cell having a chromosome number that is an exact multiple of the monoploid (n) or haploid number. Terms used to identify different levels in an euploid series are diploid, triploid, tetraploid, and so on (cf. Aneuploid).
Gametophyte
That phase of the plant life cycle that bears the gametes; the cells have n chromosomes.
Heterogametic sex
Producing unlike gametes with regard to the sex chromosomes. In humans, the XY male is heterogametic, and the XX female is homogametic.
Hfr
High-frequency recombination strain of Escherichia coli; in such strains, the F episome is integrated into the bacterial chromosome.
Homogametic sex
Producing like gametes with regard to the sex chromosomes (cf. Heterogametic sex).
Hybrid dysgenesis
In Drosophila, a syndrome of abnormal germline traits, including mutation, chromosome breakage, and sterility, which results from transposable element activity.
kinetochore microtubule
In the mitotic or meiotic spindle, a microtubule that connects the spindle pole to the kinetochore of a chromosome.
Klinefelter syndrome
A condition produced when two X chromosomes and one Y chromosome are present in the human karyotype.
lampbrush chromosome
Huge chromosome paired in preparation for meiosis, found in immature amphibian eggs; consisting of large loops of chromatin extending out from a linear central axis.
Linkage equilibrium
A state in which the alleles of linked loci are randomized with respect to each other on the chromosomes of a population.
meiosis I
The first of two rounds of chromosome segregation following meiotic chromosome duplication; segregates the homologs, each composed of a tightly linked pair of sister chromatids.
meiosis II
The second of two rounds of chromosome segregation following meiotic chromosome duplication; segregates the sister chromatids of each homolog.
Metacentric chromosome
A chromosome with the centromere near the middle and two arms of about equal length.
Metafemale (superfemale)
In Drosophila, abnormal female, usually sterile, with an excess of X chromosomes compared with sets of autosomes (for example, XXX; AA).
Metaphase
That stage of cell division in which the chromosomes are most discrete and arranged in an equatorial plate; stage following prophase and preceding anaphase.
Metaphase I
The stage during the first meiotic division when duplicated homologous chromosomes that have paired condense and gather at the equatorial plane of the cell.
Metaphase II
The stage during the second meiotic division when duplicated chromosomes gather at the equatorial plane of the cell.
mitotic chromosome
Highly condensed duplicated chromosome as seen at mitosis, consisting of two sister chromatids held together at the centromere.
mitotic spindle
Bipolar array of microtubules and associated molecules that forms in a eukaryotic cell during mitosis and serves to move the duplicated chromosomes apart.
Monosomic
A diploid cell or organism lacking one chromosome of its proper complement (chromosome formula 2n − 1). A specific case of this condition is called a monosomy (pl. monosomies).
Nullisomic
An otherwise diploid cell or organism lacking both members of a chromosome pair (chromosome formula 2n − 2).
Pachynema (adj, pachytene)
A mid-prophase stage in meiosis immediately following zygonema and preceding diplonema. In favorable microscopic preparations, the chromosomes are visible as long, paired threads. Rarely, four chromatids are detectable.
pairing
In meiosis, the lining up of the two homologous chromosomes along their length.
Paracentric inversion
An inversion that is entirely within one arm of a chromosome and does not include the centromere.
Pericentric inversion
An inversion including the centromere, hence involving both arms of a chromosome.
Phagemids
Cloning vectors that contain components derived from both phage chromosomes and plasmids.
Philadelphia chromosome
A chromosomal translocation in patients with chronic myelogenous leukemia.
Prophase I
The stage during the first meiotic division when duplicated chromosomes condense and pair with their homologues.
Prophase II
The stage during the second meiotic division when duplicated chromosomes condense and prepare to move to the equatorial plane of the cell.
replicative form
Any of the full-length structural forms of a viral chromosome that serve as distinct replication intermediates.
Robertsonian translocation
A rearrangement in which the long arms of two nonhomologous chromosomes have been joined at or near their centromeres and the short arms of these chromosomes have been lost.
Segregation (v, segregate)
The separation of paternal and maternal chromosomes from each other at meiosis; the separation of alleles from each other in heterozygotes; the occurrence of different phenotypes among offspring, resulting from chromosome or allele separation in their heterozygous parents; Mendel’s first principle of inheritance.
Sex chromosomes
Chromosomes that are connected with the determination of sex.
Spindle
A system of microtubules that distributes duplicated chromosomes equally and exactly to each of the daughters of a dividing eukaryotic cell.
spindle assembly checkpoint
Regulatory system that operates during mitosis to ensure that all chromosomes are properly attached to the spindle before sister-chromatid separation starts.
Synapsis
The pairing of homologous chromosomes in the meiotic prophase.
synaptonemal complex
Structure that holds paired homologous chromosomes tightly together in pachytene of prophase I in meiosis and promotes the final steps of crossingover.
Telophase I
The stage during the first meiotic division when duplicated chromosomes gather at the pole of a dividing cell and begin to decondense.
Telophase II
The stage during the second meiotic division when the chromosomes gather at the pole of a dividing cell and begin to decondense.
Tetrasomic (noun, tetrasome)
Pertaining to a nucleus or an organism with four members of one of its chromosomes, whereas the remainder of its chromosome complement is diploid. (Chromosome formula: 2n + 2).
Trisomic
An otherwise diploid cell or organism that has an extra chromosome of one pair (chromosome formula: 2n + 1). A specific case of this condition is called a trisomy (pl. trisomies).
Trivalent
An association between three chromosomes during meiosis.
Univalent
An unpaired chromosome at meiosis.
X chromosome
A chromosome associated with sex determination. In most animals, the female has two, and the male has one X chromosome.
X-inactivation
Inactivation of one copy of the X chromosome in the somatic cells of female mammals.
X-inactivation center (XIC)
Site in an X chromosome at which inactivation is initiated and spreads outward.
Y chromosome
The partner of the X chromosome in the male of many animal species.
