Answer:
a) Y-STR analysis
b) No, but it can rule out if he did <em>not</em>
c) Because his daughter cannot pass a Y chromosome on
d) mitochondrial DNA analysis
Explanation:
a) Because they are tracing male lineage, they are likely carrying out Y STR analysis, which looks at short tandem repeats (STRs) on the Y chromosome. Because the Y chromosome doesn't participate in crossing over, it can be reliably traced back generations and trace the paternal line, because it undergoes very little changes over time.
b) Y-STR analysis is not the best for narrowing complete specificity to one person. The Y chromosome is highly unchanged throughout generations, so it is difficult to determine differences between closely related males. However, it can rule out paternity if the Y-STRs between tested males do not match
c) Only his daughter went on to produce direct descendants still alive today. Because she is female, she could not have harbored the Jefferson Y chromosome, any of her male children will have the Y chromosome of <em>their </em>father. Therefore, they have to look at a male elsewhere in the Jefferson family to match the Y chromosomes, hence the paternal uncle.
d) Mitochondrial DNA is often used to trace maternal ancestry. Mitochondria are organelles in the cell that possess a small amount of DNA. This DNA is passed on through the maternal line (because when the sperm and egg fuse during fertilisation, the egg has thousands more mitochondria in the cell, and therefore contributes thousands of times more mtDNA than the sperm).
