Chapter 2 Problems

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2.4 (a) The coat colors of the cloned cats could be black, black/white, orange, or orange/white. There will not be any calico coloring like Rainbow (the donor). (b) Even if the X-linked inactivation was reveresed in Rainbow's cells prior to cloing, the cloned cat coat's color would not be identical to Rainbow's. The cloned cat would have her own distinct color patterns and could potentially be a calico. This is because X-inactivation occurs randomly in all cells, so no two animals will have the same color pattern. (c) Natural born, monozygotic twin daughters of Rainbow will not have the exact same coat patterns. (X- chromosome inactivation occurs are random in every cell) (d)
2.5 (I may not be answering this in the correct context..) There are three definitions of species that I deduced from p.66 in the textbook, and they are 1. geographical isolation (if two or more popoulations are geographically isolated then there is a potential for the development of different species), 2. phenotypes (populations that have similar traits are often the same species), and 3. genomic sequences (genetic sequences can give clues on the linage of a species and whether and when new populations diverge). Looking at these three defintions, I would say that genomic sequence would best match the defintion of a transitive relationship (A=B=C) because genetic sequence is passed on through the generations and memebers of a species can mate and produce fertile offspring that is also capable of passing on it's genes, even if "A" mates with "C" or any combination of the A,B,C populations. Geographical locations and phenotype do not follow the A=B=C rule because there are populations of the same species that are in different geographical locations that cannot interbreed and produce fertile young (the Larus gull example in the book), and phenotypically similar populations do not always result in a succesful, fertile offspring (almost every memeber of the Canis species can mate and produce fertile offspring, but a species of jackal cannot mate with other dog species) .
2.6 virus gene delivery to humans: (a) Gene therapy can be very helpful in treatment of genetic disorders, but there are many ethical riscs that people should be aware of. Firstly, it is very hard draw a line between what is good and what is bad - what is still a genetic disorder treatment, and what is human enhancement. Another question is, who should decide what traits are normal and which constitute a disability and whether gene therapy should be allowed for enhancing basic human traits. (b) setting guidlines for gene therapy can be very tricky. It is almost impossible, to decide for which diseases gene therapy should be allowed, since even diseases, which are not considered life-threatening (or even dissatisfaction with ones own appearance) can cause serious mental difficulties and uncomfort to the pacients.