A mutation is a change that occurs in our DNA sequence, either due to mistakes when the DNA is copied or as the result of environmental factors such as UV light and cigarette smoke.
If you were born in 1929 or later, you need to work at least 10 years to become eligible for Social Security. The SSA determines eligibility with a system of credits. Basically, you earn up to four credits for every year worked, and you need a total of 40 credits to qualify for Social Security.
There is no Social Security earnings limit. Age 66 is your full retirement age so that folks CAN continue to work and draw Social Security also. You can wait longer to get to your full retirement age and full benefit payment -- but you can also consider drawing a Social Security benefit at age 66 - whether retired or still working. You can continue to work and live on your working wages -- and save the Social Security payments for later, when you aren't working and need some extra cash.