In 1905, the French biologist Lucien Cuenot discovered an interesting mutant mou
ID: 173824 • Letter: I
Question
In 1905, the French biologist Lucien Cuenot discovered an interesting mutant mouse displaying a yellow coat color. He bred the mouse and its progeny for several generations but could never obtain a pure breeding stock of yellow mice!
Normal mice have a coat color called Agouti which appears gray. When he crossed pure breeding gray Agouti mice with the yellow mouse, half the progeny had the gray Agouti coat and half had the light yellow coat. When he crossed the F1 yellow mice with each other, he found that 1/3 of the F2 progeny had the gray Agouti coat and 2/3 had the yellow coat. When he crossed the F2 yellow progeny with pure breeding Agouti mice, he found again that they produced 50% gray Agouti mice and 50% yellow mice.
A. 2 point. Based on these results, you would conclude that relative to the Agouti coat color, the Yellow coat color is: (circle the best single answer)
Completely Dominant / Incompletely Dominant / Co-dominant / Incompletely Penetrant/ Recessive
B. 3 points. Cuenot was never able to produce a pure breeding strain of yellow mice even after trying several crosses for several years. Provide a one-sentence explanation for why Cuenot was unable to obtain yellow mice but not a pure breeding stock of yellow mice.
5. (5 points) Pleiotropy In 1905, the French biologist Lucien Cuénot discovered an interesting mutant mouse displaying a yellow coat color. He bred the mouse and its progeny for several generations but could never obtain a pure breeding stock of yellow mice! Normal mice have a coat color called Agouti which appears gray. When he crossed pure breeding gray Agouti mice with the yellow mouse, half the progeny had the gray Agouti coat and half had the light yellow coat. When he crossed the F1 yellow mice with each other, he found that 1/3 of the F2 progeny had the gray Agouti coat and 2/3 had the yellow coat. When he crossed the F2 yellow progeny with pure breeding Agouti mice, he found again that they produced 50% gray Agouti mice and 50% yellow mice A. 2 point. Based on these results, you would conclude that relative to the Agouti coat color, the Yellow coat color is: (circle the best single answer) Completely Dominant Incompletely Dominant Co-dominant Incompletely Penetrant/ Recessive B. 3 points. Cuénot was never able to produce a pure breeding strain of yellow mice even after trying several crosses for several years. Provide a one-sentence explanation for why Cuénot was unable to obtain yellow mice but not a pure breeding stock of yellow miceExplanation / Answer
A) It is complete dominant. As per definition, dominant allele shows phenotype in homozygous as well as heterozygous conditions. Yellow mice are heterozygous and if they are crossed with pure bred Agouti mice, they gave half agouti and half yellow mice. This suggests that yellow allele is dominant.
B) Yellow gene in homozygous condition is lethal. So, the mice of this genotype die as tiny embryos. So, Cuenot could not obtain pure bred yellow mice.
However, yellow allele in heterozygous condition is not lethal.