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Inheritance Patterns for a Lethal Gene

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1. A short-tailed mutant of mouse was discovered. Multiple crosses of this mouse to normal mice produced 27 normal, long-tailed mice and 25 short-tailed mice. A series of crosses among short tailed mice were made and 21 short-tailed mice and 11 long-tailed mice were produced. Determine which phenotype is dominant and explain the ratios observed with regards to the genotypes of the parents in each cross

2. In a species of beetle, the wing covers can be either green, blue or turquoise. From an interbreeding, mixed, laboratory stock population, individual virgin beetles were selected and mated in specific controlled crosses to determine the inheritance of wing-cover color. The results were as follows:
Cross Parents Progeny
1 bluexgreen all blue
2 bluexblue 3/4 blue, 1/4 turquoise
3 green x green 3/4 green, 1/4 turquoise
4 blue x turquoise 1/2 blue, 1/2 turquoise
5 blue x blue 3/4 blue; 1/4 green
6 blue x green 1/2 blue,1/2 green
7 blue x green 1/2 blue, 1/4 green, 1/4 turquoise
8 turquoise x turquoise all turquoise
Suggest a hypothesis how these traits are determined which would explain all results. Write the genotypes of the parents and the progeny
Cross Parents Progeny

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Solution Summary

This solution explains the concept of lethal genes.

See Also This Related BrainMass Solution

Recessive Epistasis: Phenotypes

A locus in Australian Bearded Dragons is involved in the production of pigment. When heterozygous parents mate, 75% of the progeny are colored and the rest are albino. Another phenotype concerns the specific colors that are expressed such that when two green bearded dragons mate, 2/3 of the progeny are green and the rest are speckled green and purple. The albino dragons cannot express whatever alleles they may have that determine specific color.

When a certain line of green dragons is crossed with a certain line of albino dragons, half of the progeny were green and the other half were speckled green and purple. The green progeny were allowed to interbreed, and 24 eggs were produced. How many of each possible phenotype would you expect to see after they hatch?

How many albinos?
How many greens?
How many speckled?

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