The answer is 20. Duplicated chromosome has two sister chromatids, identical copies of the chromosome. These two chromatids are joined at the region called centromere. Therefore, one duplicated chromosome has one centromere and two sister chromatids. If there are 20 duplicated chromosomes in a cell, there will be 20 centromeres.
The biggest airlines flying to United States: American Airlines flights to United States, Delta flights to United States, Southwest Airlines flights to United States. Regions in the USA - United States. Airlines flying to the USA - United States - by city.
American Airlines is a U.S. airline. Since its merger with US Airways, the new American offers nearly 6,700 daily flights to more than 330 destinations in about 50 countries, making it the largest airline worldwide. Codeshare partner since October 2010.