Question

Distance between two linked genes is measured in map units that depict
(a)Ratio of crossing over between them
(b)Cross-over value
(c)Number of genes between them
(d)Both (b) and (c)

Answer 1

Hint: The methods used to identify the locus of a gene and the distances between genes is called gene mapping. It indicates the percentage of offspring showing recombination between a given cross's total offspring. Centimorgans or map-units calculate the distance between the two related genes.

Complete answer:
The purpose of all mapping of genomes is to place a set of molecular markers on their respective genome positions. Recombination between related genes on the chromosome can be used to map their distance apart.
The cross-over value is the percentage of crossing over that occurs between the linked genes. It demonstrates the amount of crossing over that has occurred and the relative locations of the genes on the chromosomes, therefore.

Additional Information:
One map unit is 1 percent recombination frequency.
The higher the recombination frequency (segregation) between two genetic markers, the more they are thought to be apart. By contrast, the lower the level of recombination between the markers, the smaller the physical distance between them.
Crossover's broad-scale impact is to disperse genetic differences across a population, as well as the genetic basis for selecting the most adaptable phenotypes. The value of the crossover depends on the reciprocal distance of the observed genetic loci.
So, the correct answer is, ‘Cross over value’.

Note: When genes on the same chromosome are close together they are said to be related. That means the alleles, or gene copies, will be inherited as a unit more often than not on one chromosome already together. An arbitrary unit for gene distance, usually derived from recombination percentage, but also determined by the time the gene is transferred during conjugation.