A patient is waiting for a kidney transplant. In order for the transplant to be successful, the donated kidney (the graft) must "match" with the recipient. What has to "match" between the donor and the recipient?
Why is matching tissue more difficult than matching blood types?
What will be an ideal response?
Answer: The immune system uses major histocompatibility complex (MHC) proteins to recognize self versus non-self cells and antigens. Each person has a unique set of MHC I proteins on all nucleated cells in the body. The MHC I proteins are composed of an alpha chain and a beta chain. The alpha chain is polymorphic, which means that there are many different variants, or alleles, in the human population. The HLA-A gene has over 2000 alleles in the human population. In addition, there are three genes that are expressed simultaneously for the MHC I alpha chain: HLA-A, HLA-B, and HLA-C. Each one has multiple alleles. Therefore, a person may have up to 6 different types of MHC I protein on the surface of every cell. The situation is similar for the MHC II proteins found on all antigen presenting cells, except there are 12 loci involved. The polymorphic and polygenic nature of the MHC proteins means that it is much more difficult to match tissues than it is to match blood types because of the huge number of possible combinations of the different alleles found in the human population. Red blood cells are non-nucleated and DO NOT express MHC proteins, thus blood type only needs to match a few proteins (A, B, and Rh antigens) in order to be compatible.
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Fill in the blank with the appropriate word.
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common? a. low rainfall amounts b. uniformly high temperature c. sand d. sparse vegetation e. large leafy plants
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A) 1700 B) 5800 C) 2800 D) 1300 D) 1300
Imagine that you are performing a cross involving seed texture in garden pea plants. You cross true-breeding round and wrinkled parents to obtain F1 offspring. Which of the following experimental results in terms of numbers of plants are closest to what you expect in the F2 progeny?
a) 810 round seeds b) 810 wrinkled seeds c) 405:395 round seeds:wrinkled seeds d) 610:190 round seeds:wrinkled seeds