Reciprocal crosses involving drosophila mutant small winged ( recessive) flies gave different results. Crosses between small winged males and wild type females produced only wild type flies. On the other hand, when wild type males were used for the cross, both small winged and wild type flies were seen among the progeny. Give an explanation for this result. ( Draw the crosses and expected result). If the F1 progeny from the second cross were intercrossed, what F2 progeny ratio is expected ? ( genotypic and phenotypic ratio)

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Elin HesselLv2

2 Nov 2018

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One day while perusing the grapes at my local Safeway store, I spied a mutant fruit fly that had no wings. This trait is called vestigial (vg) to fruit fly geneticists and is recessive to the wild type allele for normal wings (+). So, I captured the little devil and decided to cross this vestigial fly with one of my prized normal winged flies. All of the progeny from this cross have normal wings. What is the genotype of my prized normal winged fly? If I were to cross two of the F1s, what would the expected genotypic and phenotypic ratios of the F2 generation be? Use Morganâs method in setting up your Punnett square.

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During the course of the infamous Drosophila experiment, two students noticed a female fly that behaved in a peculiar manner. She crawled very slowly and did not fly. Realizing that this fly, collected as a virgin female, was abnormal, they did not use her in their experiment, but decided to investigate the inheritance of this tired trait. They crossed the tired female with a wild-type male and were surprised to find that all the F1 flies, male and female, exhibited the tired trait. They allowed these flies to mate and observed that all the F2 flies were tired. They generated an F3 and F4 generation. All flies were tired. Satisfied that they had a true-breeding stock, they performed reciprocal crosses with wild type. Wild-type males by tired females yielded all tired flies in the F1 and succeeding generations. However, when tired males were crossed to wild-type females, the F1 progeny were all wild type. Succeeding generations were wild type.

A. What type of inheritance is exhibited by tired? Explain. Suggest a likely location in the cell for this mutation. Explain.

During their studies, an apparently wild-type fly, a male, appeared in one of their tired stocks. Since the fly carried several other markers, these two students concluded--after much argument--that this fly was not a contaminant. They crossed this revertant male with a tired female from the pure-breeding stock. The progeny were phenotypically 50% tired and 50% wild type. Males and females were represented equally between both phenotypes.

B. Was the mutation that produced the wild-type phenotype in the unusual male dominant or recessive? Explain. What is the most likely origin of this mutation? Explain.

greyox830

Drosophila diploid 2n=8 tolerate trisomy and monosomy of their smolest chromosome 4 so all trisomic and monosomic for this chromosome are viable. However, nullisomic and tetrasomics for chromosome 4 are letal and this type of progeny never born.

Consider the segment polarity gene cubitus interruptus (ci), that affets cuticle characteristics (mutant has naked cuticle) and also alters the wing vein pattern. Consider that ci recessive mutations results in vein interraption in the wing while the ci+ wild type allows the normal vein pattern in the wing. Deduce the phenotypic proportions in the progeny of the following crosses involving trisomcs. What are the expected phenotypes and genotypes of the progeny from these different fly crosses?

Assume tat the presence ofone wild type ci+ allele is sufficient to confer the wild type wing vein pattern phenotype.

write the diagramm of the cross, genotype, phenotype

for F1 - genotypic and phenotypic ratio - # wild type (split as # diploid # trisomic or # ?) : # mutant (split as # diploid # trisomic or # ?)

1) ci+/ci+/ci x ci+/ci

2) ci/ci/ci x ci+/ci/ci

3) ci+/ci/ci x ci+/ci