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 Boeing 777-200ER painted in Oneworld livery, taxiing at Los Angeles International Airport. As of September 2015, American Airlines operates a mainline fleet of 946 aircraft, making it the largest commercial fleet in the world.It primarily operates a mix of Airbus and Boeing (including McDonnell Douglas) narrow-body and wide-body aircraft, as well as one narrow-body variant from Embraer.merican operates the fourth largest fleet of Boeing 737 Next Generation family aircraft worldwide (behind Ryanair, Southwest Airlines, and United Airlines), while having the second largest fleet of the Boeing 737-800 variant (the only Next Generation variant used by American), trailing Ryanair.