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Lampbrush chromosome. Lampbrush chromosome are a special form of chromosome found in the growing oocytes (immature eggs) of most animals, except mammals. They were first described by Walther Flemming and Ruckert in 1882. [1] Lampbrush chromosomes of tailed and tailless amphibians, birds and insects are described best of all.
These chromosomes consist of more than 1000 copies of the same chromatid that are aligned and produce alternating dark and light bands when stained. The dark bands are the chromomere. It is unknown when chromomeres first appear on the chromosome. Chromomeres can be observed best when chromosomes are highly condensed. [2]
Joseph Grafton Gall (April 14, 1928 – September 12, 2024) was an American cell biologist whose studies revealed many details of chromosome structure and function. Gall's studies were greatly facilitated by his knowledge of many different organisms because he could select the most favorable organism to study when approaching a specific question about nuclear structure.
A metaphase cell positive for the BCR/ABL rearrangement using FISH. Cytogenetics is essentially a branch of genetics, but is also a part of cell biology/cytology (a subdivision of human anatomy), that is concerned with how the chromosomes relate to cell behaviour, particularly to their behaviour during mitosis and meiosis. [1]
In humans, at least 20 of 23 chromosome ends have been shown to contain CpG islands, which are generally found at or near transcription start sites in the subtelomeric region. Within these CpG island are three repetitive DNA tracts occurring in sequence: a centromere-proximal tract of repeated 61-base-pair (bp) units; second, a more distal ...
Endoreduplication is commonly observed in cells responsible for the nourishment and protection of oocytes and embryos. It has been suggested that increased gene copy number might allow for the mass production of proteins required to meet the metabolic demands of embryogenesis and early development. [ 1 ]
Human chromosomes (grey) capped by telomeres (white). A telomere (/ ˈ t ɛ l ə m ɪər, ˈ t iː l ə-/; from Ancient Greek τέλος (télos) 'end' and μέρος (méros) 'part') is a region of repetitive nucleotide sequences associated with specialized proteins at the ends of linear chromosomes (see Sequences).
Schematic karyogram showing the human genome, with 23 chromosome pairs, and the human mitochondrial genome to scale at bottom left (annotated "MT"). Its genome is relatively tiny compared to the rest, and its copy number per human cell varies from 0 (erythrocytes) [1] up to 1,500,000 . [2