Page 7 - It's in the DNA_Neat

In the doctor’s cabin, the scientists-cum-doctor is also waiting for us. They interview
Papa and Mamma about Dadaji’s symptoms and about all the other relatives in his
family. They want to know about cousins and second cousins and if any of them
have similar symptoms. Couple of times, Papa has to call a relative to get clear
answers.
As the doctor was talking to us, the scientist was drawing a chart. I asked him about
it. Soon, he was explaining what the chart-called a pedigree chart was all about. He

made a box for each man or boy and a circle for every woman or girl. Then he drew
lines between the people who were married to each other. From each horizontal
line connecting a couple, he drew downward lines to the boxes and circles for their
children. So now, for the scientist, my family tree looked like this.

Then he colored up the boxes of people who had ataxia in red. He explained to us
that Dadaji’s DNA had a change, a mutation in a gene. Of course, he has many
such changes that made him unique, but one of them was in a gene for ataxia.
Each of us has two copies for every gene, one from the father and one from the
mother. In the case of ataxia, even one bad copy can cause the disease.