Final answer:
A three-point cross refers to a cross involving genes on three different chromosomes and is used to examine gene linkage and distances on a chromosome. By measuring recombination frequency, geneticists determine if genes are linked and calculate their distances in centimorgans.
Step-by-step explanation:
A three-point cross is a testcross that involves three different genes and is used to investigate the linkage and distance between those genes on a particular chromosome. In genetics, when determining if genes are linked, geneticists often use a three-point cross to analyze the inheritance patterns of three separate genes simultaneously in a single breeding experiment.
The correct answer to the student's question is B) cross involving genes on three different chromosomes. This method is integral for constructing genetic maps, where the frequency of recombination between genes is measured to predict their relative distances on a chromosome. Recombination frequency helps to ascertain whether genes are linked and how far apart they are, with 1% recombination frequency being equivalent to 1 centimorgan (cM).
Using a three-point cross, the recombination frequency can be higher than in a standard testcross involving only two genes because it can reveal more complex recombination events among the three genes being studied. The outcome can demonstrate whether the genes independently assort or if they are linked and segregate together.