Chromosome

About: Chromosome is a research topic. Over the lifetime, 17538 publications have been published within this topic receiving 660077 citations. The topic is also known as: chromosomes & GO:0005694.

A knob-associated tandem repeat in maize capable of forming fold-back DNA segments: are chromosome knobs megatransposons?

Abstract: A class of tandemly repeated DNA sequences (TR-1) of 350-bp unit length was isolated from the knob DNA of chromosome 9 of Zea mays L. Comparative fluorescence in situ hybridization revealed that TR-1 elements are also present in cytologically detectable knobs on other maize chromosomes in different proportions relative to the previously described 180-bp repeats. At least one knob on chromosome 4 is composed predominantly of the TR-1 repeat. In addition, several small clusters of the TR-1 and 180-bp repeats have been found in different chromosomes, some not located in obvious knob heterochromatin. Variation in restriction fragment fingerprints and copy number of the TR-1 elements was found among maize lines and among maize chromosomes. TR-1 tandem arrays up to 70 kilobases in length can be interspersed with stretches of 180-bp tandem repeat arrays. DNA sequence analysis and restriction mapping of one particular stretch of tandemly arranged TR-1 units indicate that these elements may be organized in the form of fold-back DNA segments. The TR-1 repeat shares two short segments of homology with the 180-bp repeat. The longest of these segments (31 bp; 64% identity) corresponds to the conserved region among 180-bp repeats. The polymorphism and complex structure of knob DNA suggest that, similar to the fold-back DNA-containing giant transposons in Drosophila, maize knob DNA may have some properties of transposable elements.

Definition of a tumor suppressor locus within human chromosome 3p21-p22

Abstract: Cytogenetic abnormalities and high-frequency allele losses involving the short arm of human chromosome 3 have been identified in a variety of histologically different neoplasms. These findings suggest that a tumor-suppressor gene or genes may be located in the region of 3p14-p25, although there has been no definitive functional proof for the involvement of a particular region of 3p. We report a rapid genetic assay system that has allowed functional analysis of defined regions of 3p in the suppression of tumorigenicity in vivo. Interspecific microcell hybrids containing fragments of chromosome 3p were constructed and screened for tumorigenicity in athymic nude mice. Hybrid clones were obtained that showed a dramatic tumor suppression and contained a 2-megabase fragment of human chromosomal material encompassing the region 3p21 near the interface with 3p22. With these hybrid clones, we have defined a genetic locus at 3p21-p22 intimately involved in tumor suppression.

Sex chromosome linkage of 5S rDNA in rainbow trout (Oncorhynchus mykiss)

Abstract: The karyotype of the rainbow trout is characterized by a primitive XX/XY sex-determining chromosomal system. (Thorgaard et al., 1977). In the present study using FISH we have physically linked the 5S rRNA genes to the partially undifferentiated X chromosome pair. PCR amplified 5S rDNA was used for FISH and hybridization signals indicated that the genes were duplicated, present in one acrocentric and one metacentric pair of chromosomes. After analyzing several individuals, the female metaphases showed four fluorescent signals whereas males presented only three signals. Two of the three signals obtained in males corresponded to the metacentric pair whereas the single signal was mapped to the heterochromatin that cytologically differentiates the X chromosome from the Y chromosome. Double FISH experiments demonstrated that the 5S rDNA which is not sex linked is located at the NOR bearing arm close to the major ribosomal RNA genes (5.8S, 18S and 28S), similar to the situation observed in Atlantic salmon (Pendas et al., 1994a).