Question of the Day

Down syndrome, also known as trisomy 21, is the result of an extra copy of chromosome 21. The consequences of this lead to a set of symptoms that include mild to moderate intellectual disabilities, characteristic facial features, and, quite often, cardiac abnormalities. Cystic fibrosis and baldness are also the result of hereditary changes in the chromosomal DNA inherited from parents. These diseases, however, are both caused by small changes in the DNA sequence of specific genes related to mucus production and hair growth, respectively. In contrast, Hansen’s disease, also known as leprosy, is not inherited and is caused by an infectious agent, the bacteria Mycobacterium leprae, also known as Hansen’s bacillus.