Jake Burger will wear No. 21

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 ...
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.
During this stage, one set of chromosomes is pulled to the sides of ... Topic-based exam practice questions based on GCSE OCR 21st Century past papers, giving you the option to choose the specific ...