20 10 biology contest genetic problem solving! ! !

Personal analysis of this year's genetic problems (wild jasmine), for reference only.

92. It is too absolute for A to say that the color is controlled by more than two alleles, and so is B. Because there may be one gene (multiple alleles) or two or more alleles, the CD pair, AB, is wrong, and E only exists in the case of multiple alleles, but it cannot be judged by known conditions, so it is not selected.

93.a seems to be correct, but in fact, when the genes are complementary, the offspring are not white, so B cannot be chosen, or C is too absolute because of gene complementarity. If controlled by multiple alleles and incomplete dominance, R is red, P is pink and W is white, the phenotype of RW and PP may be the same, but only RW has problems with self-intersection, and there will be no problems with hybridization and self-crossing with PP.

94. Let the genes be the same as those in the above question. A is possible, and B is possible. According to the above question, C is impossible. There is no scarlet gene in multiple alleles. D and e are the same.

95. The mutation rate of gene A is very low, so the offspring will not all be crimson. Similarly, B is impossible, because the superposition effect (when multiple pairs of genes * * * act on a certain trait, no matter how many dominant genes there are, it will affect the development of the same trait, and only negative homozygotes will show the corresponding negative traits) will make all the flowers of dominant genes turn dark red, and D is possible. Definition of gene complementation: When two dominant genes are homozygous dominant or heterozygous respectively, * * * determines the development of a character. When only one pair of genes is dominant, or both pairs of genes are recessive, it shows another trait. E is impossible, because all descendants are scarlet.

96.a can't be judged only by known conditions, so it is possible to choose B. If there are multiple alleles plus transposons, this phenomenon may indeed occur. C is wrong. If it was gene suppression, there wouldn't be so many traits. D is possible, because only a few pink flowers and shallow safflower have white spots, which is consistent with the low frequency of gene mutation. E is correct. If the gene that inhibits transposition is dominant in red and crimson, it can explain the phenomenon in the topic.

97.a is wrong and the mutation rate is low. Many white flowers can't have erythema. B is wrong. We can't be sure that it must be heterozygote. C is wrong. Refer to question 95 for gene complementation. D is wrong. Like A, E is right, and the probability of transposon affecting phenotype is much greater than that of gene mutation.

98. If the genotype is the same as that in question 93, the pollen with white spots proves that its genotype is PW, and the offspring produced by PW and WW must be 1pw: 1WW, so there are only B pairs, and E is wrong because even if transposons exist, they will not all be white spots.

99. This problem should be considered comprehensively (gene complementation, incomplete dominance, transposon, etc.). ). Erythema means heterozygosity, so there will be no case of A and B that can be considered complementary. In case of C, transposon D says that it is too absolute to only open pink flowers and white flowers, and red and crimson may appear when complementary. The explanation of e refers to d.

I hope it helps you.