<u>Answer</u>:
1. A. abc*ghijklmn
Through deletion, the part of the chromosome -def* was lost.
2. C. 0%
Two parents with B and AB will produce children with A, B or AB blood types. Never an O child. In order for this to be possible, the father would have to be A, B or O.
3. John
The gel electrophoresis method will separate the DNA according to molecular size. This pattern is unique to each individual.
4. B. Abnormal female - 47 chromosomes.
On chromosome pair 21 it can be observed a third copy of this chromosome. This is caused by the Down syndrome, also known as trisomy 21. It is a female, because the last chromosome pair, number 23 has two identical copies, commonly denoted as XX.