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.
The most recently built aircraft flying from MEM to ORD in 2009 was Embraer's EMB-170 flown by Shuttle America. The EMB-170 took flight for the first time in 2004. The longest flying aircraft flying from Memphis, TN to Chicago, IL during the 2009 year was a McdonnellOuglas' MD-80 flown by American Airlines.