Conventional Cytogenetic Report

This report is studying about conventional cytogenetic, and we will focus on a technique called ‘karyotyping’. This repot is going to introduce about the definition, the history and the improvements of karyotyping made before, what is the process and the working principle of this technique and also how if can be applied in our daily life. Karyotyping is a test to examine chromosomes in a sample of cells, which can help identify genetic problems as the cause of a disorder or disease. The term ‘karyotyping’ is come from ‘karyotype’, which is the characteristic chromosome complement of a eukaryote species.
The preparation and study of karyotypes is part of cytogenetics. In the middle and late 18th century, scientists were aware of the presence of chromosomes but had difficulty studying them because of their extremely small size. Chromosomes were first observed in plant cells by a scientist called Karl Wilhelm von Nageli in 1842, but since the samples they took had small chromosomes. After the development of genetics in the early 20th century, when it was appreciated that the set of chromosomes, the karyotype was the carrier of the genes.
Another scientist Levitsky seems to have been the first to define the karyotype as the phenotypic appearance of the somatic chromosomes, in contrast to their genic contents. It took until the middle 1950s until it became generally accepted that the karyotype of humans included only 46 chromosomes. Rather interestingly, the great apes have 48 chromosomes. Human chromosome 2 was formed by a merger of ancestral chromosomes, which reducing the number. Investigation into the human karyotype took many years to settle by two famous scientists: Hans von Winiwarter and Theophilus Shickel Painter.

Hans von Winiwarter examined normal human diploid cells to try and define the number of chromosomes that humans have. In his time, guesses ranged from 16 to 36. He used the most powerful microscopes available in his day in one of the first accurate karyotyping attempts, and counted specifically between 46 and 49 chromosomes in his samples in 1912. He concluded that females had two X chromosomes and males had only one X chromosome and no Y chromosome. Theophilus Shickel Painter in 1922 was not certain whether the diploid number of humans was 46 or 48, at first favouring 46.
He revised his opinion later from 46 to 48, and he correctly insisted on humans having an XX/XY system. And there are two advanced skills in karyotyping. The first one is Single-Nucleotide Polymorphism (SNP), this method is going to investigate the use of virtual karyotypes for diagnostically challenging renal epithelial tumors. First is to evaluate 25 archived renal neoplasms where sub-classification could not be rendered based on morphology and other ancillary studies. Then it will generate virtual karyotypes with the Affymetrix 10 K 2. 0 mapping array platform and identify the presence of genomic lesions across all 22 autosomes.
The second one is Comparative Genomic Hybridization (CGH), it is going to scan the entire genome for variations in DNA copy number. Total genomic DNA is isolated from test and reference cell populations, differentially labeled and hybridized to metaphase chromosomes or DNA microarrays. The relative hybridization intensity of the test and reference signals at a given location is then proportional to relative copy number of those sequences in the test and reference genomes. The increases and decreases in the intensity ratio directly indicate DNA copy-number variation in the genome of the test cells.