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.
Southwest Airlines is a low-cost air carrier that offers nearly 3,400 flights per day to 72 cities in 37 states. Incorporated in 1971, the airline specializes in domestic flights, with its biggest departure airports being in Chicago (Midway), Las Vegas, Baltimore/Washington and Phoenix.