Chromosome 21 is the smallest human chromosome, and procedures for examining human chromosomes were still being developed during the first part of the century. Many early cytologists had ...

According to the CDC, here is why No. 21 is significant in this case: Down syndrome is a condition in which a person has an extra copy of chromosome 21. Chromosomes are small "packages" of genes ...

Most people have two copies of each chromosome, for a total of 46. People with Down syndrome have 3 copies of the 21st chromosome, making a total of 47. Down syndrome is also called Trisomy 21.

which involves the triplication of the 21st chromosome. Celebrated annually on March 21st, this day holds significant importance in highlighting the achievements, challenges, and contributions of ...

Every year, about 7.9 million infants (6% of worldwide births) are born with serious birth defects. With the causes of over 50% of birth defects unknown, how do we diagnose and prevent them?

Photograph of a karyotype - the collection of chromosomes within each cell of an organism - from a male mouse engineered by Johns Hopkins Medicine researchers to model Down syndrome in a human.

And the three chevrons on the Barbie’s necklace represent how people with Down’s syndrome have three copies of their 21st chromosome, Mattel said. In addition, the Barbie wears ankle foot ...