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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.
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.
These intensive RNA biosynthese are mirrored in the structure of the chromosomes, which decondense and form lateral loops giving them a lampbrush appearance (see Lampbrush chromosome). Oocyte maturation is the following phase of oocyte development. It occurs at sexual maturity when hormones stimulate the oocyte to complete meiotic division I.
Although found all across the lampbrush chromosome, they are not organized in a clear pattern along as they are in normal pachytene chromosomes of meiosis. [2] [5] The two sister chromatids of a lampbrush chromosome separate fully, forming lateral loops that extend from chromomeres, and act as transcription complexes. The lateral loops are ...
Other numerical abnormalities discovered include sex chromosome abnormalities. A female with only one X chromosome has Turner syndrome, whereas a male with an additional X chromosome, resulting in 47 total chromosomes, has Klinefelter syndrome. Many other sex chromosome combinations are compatible with live birth including XXX, XYY, and
In the 1940s and early 1950s, experiments pointed to DNA as the portion of chromosomes (and perhaps other nucleoproteins) that held genes. A focus on new model organisms such as viruses and bacteria, along with the discovery of the double helical structure of DNA in 1953, marked the transition to the era of molecular genetics.
Thomas Hunt Morgan (September 25, 1866 – December 4, 1945) [2] was an American evolutionary biologist, geneticist, embryologist, and science author who won the Nobel Prize in Physiology or Medicine in 1933 for discoveries elucidating the role that the chromosome plays in heredity.
1955: Joe Hin Tjio, while working in Albert Levan's lab, determined the number of chromosomes in humans to be of 46. Tjio was attempting to refine an established technique to separate chromosomes onto glass slides by conducting a study of human embryonic lung tissue, when he saw that there were 46 chromosomes rather than 48.