A plantlike organism on the planet Pandora can have three recessive genetic traits: bluish leaves,due to an allele (a)of gene A;a feathered stem,due to an allele (b)of gene B;and hollow roots,due to an allele (c)of gene C.The three genes are linked and recombine.
A geneticist did a testcross with an organism that had been found to be heterozygous for the three recessive traits and was able to identify progeny of the phenotypic distribution (+ = wild type)shown in the figure below.
The greatest distance among the three genes is between a and c.What does this mean?
A)Gene c is between a and b.
B)Genes are in the order: a-b-c.
C)Gene a is not recombining with c.
D)Gene a is between b and c.

Question

A plantlike organism on the planet Pandora can have three recessive genetic traits: bluish leaves,due to an allele (a)of gene A;a feathered stem,due to an allele (b)of gene B;and hollow roots,due to an allele (c)of gene C.The three genes are linked and recombine.
A geneticist did a testcross with an organism that had been found to be heterozygous for the three recessive traits and was able to identify progeny of the phenotypic distribution (+ = wild type)shown in the figure below. 
The greatest distance among the three genes is between a and c.What does this mean?
A)Gene c is between a and b. 
B)Genes are in the order: a-b-c. 
C)Gene a is not recombining with c. 
D)Gene a is between b and c.

Quizplus · Accepted Answer

The greatest distance among the three genes is indicated by the progeny with the least frequent phenotype, in this case acbc. Since these progeny are the result of a double crossover event, they must have experienced recombination between genes A and C. Therefore, genes A and C are furthest apart and are in the order a-b-c.

A Plantlike Organism on the Planet Pandora Can Have Three