Figure Detail. As mentioned, sickle-cell anemia is the result of a change in a single nucleotide, and it represents just one class of mutations called point mutations. Changes in the DNA sequence can also occur at the level of the chromosome, in which large segments of chromosomes are altered.he result is the deletion of a DNA sequence in one chromosome, and the insertion of a DNA sequence in the other chromosome. Â© 2014 Nature Education Adapted from Pierce, Benjamin. Genetics: A Conceptual Approach, 2nd ed.
Also established in 1984, the Texas Division of Southwestern Bell Telephone, with headquarters at Dallas, became one of the largest nongovernmental employers in the state, serving 6.2 million customers in 549 Texas communities.
The Bell System was the system of companies, led by the Bell Telephone Company and later by AT&T, which provided telephone services to much of the United States and Canada from 1877 to 1984, at various times as a monopoly. On December 31, 1983, the system was divided into independent companies by a U.S. Justice Department mandate. The general public in the United States often used the colloquial term Ma Bell to refer to any aspect of this conglomerate, as it held a near-complete monopoly over te