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.
How Social Security benefits are calculated. In order to be eligible for Social Security retirement benefits, you'll need to earn a total of 40 credits over the course of your working lifetime. In 2017, you'll get one credit for every $1,300 in Social Security taxable earnings, and there is a maximum of four per year. So, to become eligible, you'll need to work for at least 10 years with earnings of at least $5,200 per year.