On October 5, the National Zoo announced the sex of Mei Xiang’s newest cub. The cub was born on August 21. DNA testing was used to determine it is a boy. This test is the best way to tell the gender since male and female panda cubs look alike. Their outward genitalia doesn’t appear until they are several months old. During a wellness checkup, vets collected a cheek swab from the cub. This was analyzed to find a zinc finger protein gene. The DNA sequence of this gene had both X and Y chromosomes, which meant the cub was a male.