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.
It is Arizona's largest and busiest airport, and the largest commercial airport in the American Southwest. The airport is the primary regional hub and gateway for Mexican and Hawaiian departures for Tempe-based US Airways and is a focus city for Southwest Airlines. US Airways is the airport's largest carrier. In 2012, the airport served 40,421,611 passengers, making it the ninth busiest in the United States in terms of passengers and one of the top 15 busiest airports in the world with a 90 million dollar daily economic impact.