A small cell lived inside a larger cell to the benefit of both cells.
Hope this helps!
When a doctor refuses to care for a certain patient. This can be for numerous reasons, maybe they are not fit to undergo a surgery of some sort, or are being problematic. Either or the doctor nor the patient benefit form this. Doctor misses out on someone to help (i assume that’s the attitude of one working for the greater good) and the patient misses the opportunity to possibly get the help they need.
Both parents must be carriers, which means they have the heterozygous gene (one uppercase letter & one lower case letter). They will still carry that mutated gene (because they have a lower case letter), and their offspring will have a 25% chance of getting a recessive disorder. The percentage is low but still possible.