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.
United will use the world's most advanced passenger airplane, the Boeing 787-9 Dreamliner, to operate the service. Measured by distance, the San Francisco - Singapore service will be the longest scheduled 787 flight operated by any airline and the longest scheduled flight operated by any U.S. carrier, at 8,446 miles.