Answer: Option B
:
B
Morgan conducted experiments on Drosophila related to X-linked inheritance. He suggested that the frequency of crossing over between two genes depends on distance between them.Physical crossing over during meiosis I is a normal event. The effect of this event is to rearrange heterozygous homologous chromsomes into new combinations. The term used for crossing over isrecombination. 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 the number of crossover gametes. Therefore, determination of percentage of crossing over gives an idea about the position of genes on chromosomes.