DNA analysis is the process in which genetic sequences are studied. It is used by law enforcement and medical personnel to identify a particular person or species, and even specific cancers and diseases. At one point the analysis process was very limited.
To round off to the nearest tenth, means to keep one decimal digit. (To round off to the nearest hundredth would mean to keep two digits; to the nearest thousandth, three; and so on. Now, the digit in the second decimal place is 5. Therefore add 1 to the previous digit 2.
To smother is to overwhelm or suffocate. If you've ever had a boyfriend or girlfriend who calls you twenty five times an hour to check up on you, then you know what it means to be smothered by someone. The word smother literally means to deprive of oxygen, so it can be used to refer to someone who gets suffocated by a pillow.