single-gene disorder or monogenic disorder Some disorders result when a mutation causes the product of a single gene to be altered or missing. These disorders are inherited in simple patterns similar to or identical with those described by Mendel for certain discrete characteristics in garden peas. Therefore it's also called mendelian diseases
The most common gene change involves a single base mismatch--a misspelling--placing the wrong base in the DNA. At other times, a single base may be dropped or added. And sometimes large pieces of DNA are mistakenly repeated or deleted
About the final It will be in English. Try to answer in English as well. The problems are given in such a way that very short answers are needed. Chinese allowed if you can only read English