Final answer:
A three-point cross is superior because it provides more detailed information on gene order and distances on a chromosome by tracking three genes at once, thus allowing for the detection of double crossovers and increased accuracy in linkage maps.
Step-by-step explanation:
Advantages of a Three-Point Cross
In regards to gene linkage, a three-point cross is considered superior to a two-point cross because it provides more information about the order of genes on a chromosome and the distances between them. A three-point cross involves tracking three different genes simultaneously, rather than just two as in a two-point cross. This allows geneticists to observe multiple crossover events between these genes. Additionally, it helps in constructing more accurate linkage maps because it is possible to detect double crossovers, which can be missed in a two-point cross. Double crossovers can reveal the true order of genes by showing which genes are in the middle, and hence allows for a more precise determination of genetic distance.
Through a three-point cross, not only can the existence of gene linkage be confirmed, but the frequency of recombinant gametes can give insight into the physical distance between linked genes. Since crossing over is more likely to occur between genes that are further apart, closely linked genes will have fewer recombinant gametes. Thus, by comparing the number of parental type offspring to recombinant type offspring, geneticists can deduce the distances between genes on a chromosome with greater accuracy.