Ria was studying about $DNA$ in her textbook,learning that $DNA$ molecules are responsible for constructing and organizing cells and are present as part of chromatin material in the nucleus to transfer hereditary information. Ria was confused about how she could know if she possesses all the hereditary information from her parents. Her mother explained that through their hair or cells,the $DNA$ of parents and a child can be matched.
$(a)$ What kind of qualities are shown by Ria's mother?
$(b)$ In which part of a cell is $DNA$ found? State its function.