Dna Karyotyping

1. Gel electrophoresis is used to sort DNA strands according to length. By adding an electrical current to the gel filter, the strands begin to move in a motion called reptation. Phosphates in DNA give it a negative charge. The negatively charged DNA moves towards the positively charged pole in the electrophoresis chamber. The shorter strands move the fastest. Over time, the shortest strands will have moved the furthest away from the starting point while the longest strands are closest. Strands of the same length move at the same speed.

2. Variable number tandem repeats are sequences of two base pairs that are repeated a certain amount of time throughout a strand of DNA. This is useful in this case to determine why one of the twins looks so different than the other.

3. Each “band” on the gel represents a group of stained DNA strands of the same length. It is important to run multiple gels because two bands could be the same by coincidence. If the bands are the same in multiple gels, you can determine that the similarity is not a coincidence but actual genetic evidence. And as always, any scientific experiment should be repeated for accuracy.

4. A conclusion can be drawn that Nathan is not Darrell’s father. Darrell shares bands with Hannah on multiple occasions which proves that she is his mother. Thomas also shares bands with both Hannah and Nathan on multiple occasions. Darrell and Thomas even share a band once. This is eliminated because Hannah is in fact Darrell’s biological mother. I believe that the mixup occurred during fertilization. The evidence points in the direction that one of Hannah’s eggs (Darrell’s) was fertilized by a different man other than Nathan. This would explain why Darrell shares no bands with his “father” Nathan.