A three point cross was performed using fruit flies. The three loci are physically linked on the same autosome. The d allele, in the homozygous state, results in the recessive âdouble dorsalâ phenotype. Similarly, the r allele results in the recessive âround earsâ phenotype and the e allele in the recessive âendless eyeâ phenotype. In contrast, the D, R, and E alleles encode for the dominant wild type phenotypes at each of these loci.
True breeding (homozygous) flies were crossed to produce F1 offspring. Due to poor book-keeping, the genotypes of the parent flies were not recorded â but one parent fly had one mutant phenotype, while the other parent had the other two mutant phenotypes.
Phenotype Number of F2 Flies
Ears Dorsal Eyes
1) Round ears Double Dorsal Endless Eyes 230
2) Wild-type Wild-type Wild-type 260
3) Round ears Wild-type Wild-type 4,390
4) Wild-type Double Dorsal Endless Eyes 4,100
5) Round ears Double Dorsal Wild-type 15
6) Wild-type Wild-type Endless Eyes 15
7) Round ears Wild-type Endless Eyes 510
8) Wild-type Double Dorsal Wild-type 480
10,000 total
a) What is the phenotype of the F1 flies?
b) What is the genotype of the F1 flies? Your answer should indicate the phase of linkage.
c) What are the genotypes and phenotypes of the original parent flies (previously not recorded)? Your answer should indicate the phase of linkage.
d) Calculate the map distance in cM between each of the three loci and determine the gene order. Show all work for full credit. (6 points)
A three point cross was performed using fruit flies. The three loci are physically linked on the same autosome. The d allele, in the homozygous state, results in the recessive âdouble dorsalâ phenotype. Similarly, the r allele results in the recessive âround earsâ phenotype and the e allele in the recessive âendless eyeâ phenotype. In contrast, the D, R, and E alleles encode for the dominant wild type phenotypes at each of these loci.
True breeding (homozygous) flies were crossed to produce F1 offspring. Due to poor book-keeping, the genotypes of the parent flies were not recorded â but one parent fly had one mutant phenotype, while the other parent had the other two mutant phenotypes.
Phenotype Number of F2 Flies
Ears Dorsal Eyes
1) Round ears Double Dorsal Endless Eyes 230
2) Wild-type Wild-type Wild-type 260
3) Round ears Wild-type Wild-type 4,390
4) Wild-type Double Dorsal Endless Eyes 4,100
5) Round ears Double Dorsal Wild-type 15
6) Wild-type Wild-type Endless Eyes 15
7) Round ears Wild-type Endless Eyes 510
8) Wild-type Double Dorsal Wild-type 480
10,000 total
a) What is the phenotype of the F1 flies?
b) What is the genotype of the F1 flies? Your answer should indicate the phase of linkage.
c) What are the genotypes and phenotypes of the original parent flies (previously not recorded)? Your answer should indicate the phase of linkage.
d) Calculate the map distance in cM between each of the three loci and determine the gene order. Show all work for full credit. (6 points)
Related textbook solutions
Related questions
In Drosophila, the map positions of genes are given in map units numbering from one end of a chromosome to the other. The X chromosome of Drosophila is 66 m.u.. long. The X-linked gene for body color-with two alleles, y +for gray body and y for yellow body-resides at one end of the chromosome at map position 0.0. A nearby locus for eye color, with alleles w +for red eye and w for white eye, is located at map position 1.5. A third X-linked gene, controlling bristle form, with f + for normal bristles and f for forked bristles, is located at map position 56.7. Each gene resides on the Xchromosome, and at each locus the wild-type allele is dominant over the mutant allele.
Predict the frequency of gray with white eyes and forked bristles progeny type produced by this mating.
Enter your answer as a percentage to three decimal places (example 0.235 or 0.230).
Frequency=_________
2.
| Phenotype | Number |
| Pale | 648 |
| Pale, oval | 64 |
| Pale, short | 10 |
| Pale, oval, short | 102 |
| Oval | 6 |
| Oval, short | 618 |
| Short | 84 |
| Wild type | 98 |
| 1630 |
A wild-type trihybrid soybean plant is crossed to a pure-breeding soybean plant with the recessive phenotypes pale leaf l, oval seed (r), and short height (t). The results of the three-point test cross are shown in the table. Traits not listed are wild type.
Calculate the interference value for these data.
Enter your answer to three decimal places (example 0.201).
