DNA - (May/27/2007 )
To determine the identity of their biological parents, adopted children sometimes request DNA tests. These tests involve comparing DNA samples from the child to DNA samples taken from the likely parents. Possible relationships may be determined from these tests because the (1) DNA of parents and their offspring is more similar than the DNA of nonfamily members. (2) position of the genes on each chromosome is unique to each family. There were four choices for this quesiton, but i think these two are the possible answers. However, i had known that (1) is right, but i chose (2), the position of genes, i consider it as allele. I don't know why (2) is wrong. Hope you can tell me, thanks.
Gene position is an important issue when considering the relatedness of different organisms, and has been used to help determine such things as how long ago chimpanzees and humans diverged etc. The next stage of examination is the determination of which chromosome a particular gene is on. As organisms diverge more and more, or as more time passes, the likelihood of chromosomal rearrangements increases.
To shift genes within a chromosome requires some fairly major re-arrangement of the chromosome. Imagine what would happen at meiosis: the risk of localised trisomy or monosomy would be so great that the embryo's likelihood of being viable would be virtually non-existent.