Crossing over often occurs during prophase. how could scientists use an easy to measure trait that is linked to the gene responsible for a certain genetic condition to locate the disease causing gene?

Crossing over is the phenomena of the exchange of the genetic material between the non sister chromatid of the homologous chromosomes. The crossing over results in the  formation of recombinant progeny.

Linked traits are  close to each other and present on the same chromosome. The linked traits that are very close to each other and will not separate by the process of crossing over. This information is used to locate the disease condition.

answer-

the statement that f(x) = |x+a| + b has exactly one x-intercept is sometimes correct.

solution-

it solely depends on b, whether the function will have one or two or zero x intercept.

this plot of the given function, f(x) = |x+a| + b will be the basic absolute value graph i.e v shape, with vertex translated to (-a, b), instead of origin.

1-   if b is zero, the graph will have exactly one x-intercept, at x= -a

2- if b is positive, the whole graph will be above the x-axis, hence it will have no x-intercepts.

3- if b is negative, the graph will be below the x-axis, hence it will have two x-intercepts.

∴ the statement is sometimes true.