You discover a recessive mutation that results in roses with no thorns (n). Investigating the genetics of roses you find that the color of red roses is determined by 2 genes; the color enzyme gene and the pigment synthesis gene. A dominant mutation (R) in the color enzyme converts pigment from blue to red.  However, the synthesis gene (Y) is required for making pigment and a recessive mutation (y) in the synthesis gene causes no pigment (white). The syn gene is epistatic to the color enzyme gene. Thinking you could dominate the valentine day rose market, you intercross a red rose that is tri-heterozygous for your no-thorn mutation, the color enzyme gene and the synthesis gene, all of which are found on different chromosomes. Although many of your n/n plants have no thorns (70%), the other 30% have less thorns ranging from 1-2 to approximately half of normal. What explains these observations? A. Penotypic variability  B. Incomplete penetrance C. Incomplete dominance D. Maternal effect

Human Heredity: Principles and Issues (MindTap Course List)
11th Edition
ISBN:9781305251052
Author:Michael Cummings
Publisher:Michael Cummings
Chapter15: Genomes And Genomics
Section: Chapter Questions
Problem 14QP
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You discover a recessive mutation that results in roses with no thorns (n). Investigating the genetics of roses you find that the color of red roses is determined by 2 genes; the color enzyme gene and the pigment synthesis gene. A dominant mutation (R) in the color enzyme converts pigment from blue to red.  However, the synthesis gene (Y) is required for making pigment and a recessive mutation (y) in the synthesis gene causes no pigment (white). The syn gene is epistatic to the color enzyme gene. Thinking you could dominate the valentine day rose market, you intercross a red rose that is tri-heterozygous for your no-thorn mutation, the color enzyme gene and the synthesis gene, all of which are found on different chromosomes. Although many of your n/n plants have no thorns (70%), the other 30% have less thorns ranging from 1-2 to approximately half of normal. What explains these observations?

A. Penotypic variability 

B. Incomplete penetrance

C. Incomplete dominance

D. Maternal effect

E. None of the above

Expert Solution
Step 1

No thorns is a recessive mutation. Homozygous condition of the gene (nn) produces roses with no thorns. In the given experiment not all n/n plants were lacking thorns. 70% of them have no thorns while other 30% shown lesser number of thorns.

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