Correct Answer: B
Explanation:
Physical crossing over during meiosis I is a normal event. The effect of this event is to rearrange heterozygous homologous chromosomes into new combinations. The term used for crossing over is recombination. Recombination can occur between any two genes on a chromosome, the amount of crossing over is a function of how close the genes are to each other on the chromosome. If two genes are far apart, for example at opposite ends of the chromosome, crossover and non-crossover events will occur in equal frequency. Genes that are closer together undergo fewer crossing over events and non-crossover gametes will exceed than the number of crossover gametes. The figure shows this concept.
Finally, for two genes are right next to each other on the chromosome crossing over will be a very rare event.