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In Drosophila, the gene for bar-shaped (B) eyes and the gene for scalloped wings (sc) are linked on the X-chromosome. (The normal or wild type eye shape is oval, and the wild type wing is rounded.) Heterozygous, bar-eyed females were mated to homozygous, scalloped-wing males. The offspring are as follows:

phenotype female male
scallop 183 186
bar 189 188
wild type 12 10
scallop & bar 9 12

-What is the map distance between the two genes?

-Give the exact phenotypes of the F1 flies.

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Deanna Hettinger
Deanna HettingerLv2
28 Sep 2019

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Related questions

1. A mutant fruit fly strain has short wings. Males ofthis strainare mated to females that have long (wild type) wings. All of theF1 offspring have long wings. When F1 males and female are mated,they producelong andshort wing offspring in a 3:1ratio.

Is the short wing mutation dominant or recessive withrespectto thewild type wing length?Explain.

Assign allele designations and write out the genotypes forthe parentaland F1 crosses. What are the genotypes of the F2offpsring?

2. A male fruit fly with bar-shaped eyes is mated to afemale with wild type round eyes. All the F1female offspringhave bar-shaped eyes and all of the F1 male offspring have roundeyes. When the F1 males and females are mated with each other, theF2 offspringare ofthe following phenotypes and ratios:

The miniature wing gene in Drosophila is on the X chromosome. It is recessive. Normal sized wings (wild type) is completely dominant over miniature wings. A HETEROZYGOUS normal winged female is mated to a wild type male. What would be the phenotypes of the offspring?

I know the answer is males with half mini and half wt wings, and females with all wt wings. I just need to know how you get that answer.

Answer the following Linked to sex genetics problems:

1.) In Drosophila the recessive mutation linked to the X chromosome, scalloped ( sd ), causes the edge of the wings to be irregular. Present the results (you must prepare the crossing scheme) phenotypic for F1 and F2 for a cross between:

A) female scallop and a normal male (regular edges)

B) A normal (homozygous) female and a scallop male .

C) Compare these results with those that would be obtained if scallop were an autosomal recessive mutation.

2.) In Drosophila the autosomal recessive ebony mutation (e) is located on chromosome 3 and produces a dark body in the fly that expresses it. What will be the phenotypic proportions for F1 and F2 that will be obtained from a cross between a scallop female and homozygous for a normal body, with an ebony male with normal wings? Solve by the bifurcated lines method.

3.) In Drosophila the recessive mutation linked to the vermilion X chromosome (v) produces bright red colored eyes in contrast to the wild phenotype that has brick red eyes. An autosomal recessive mutation, suppressor vermilion (su-v) causes homozygous or hemizygous males to females present vermilion red brick eyes. In the absence of the vermilion allele su-v has no effect on the phenotype of the eye. Determine the genotype and phenotype of F1 and F2 at a cross between a homozygous female for vermilion and su-v, with a vermilion male and wild homozygous for su-v (su-v + su-v + ) . Present the diagram of bifurcated lines for these crosses.

4.) At a crossroads with Drosophila involving recessive mutations white (linked to the X chromosome) and sepia (autosomal recessive) that produces dark eyes, predict the results of F1 and F2 when crossing pure parents with the following phenotypes.

A.) White females with sepia males.

B.) Sepia females with white males

5.) Two mothers have given birth to their children at the same time in an urban hospital with an excess of patients. The child of couple 1 has hemophilia, a condition caused by a recessive allele linked to the X chromosome. Neither parent has the condition. Couple 2 has a normal child even though the father is a hemophiliac. Several years later, couple 1 filed a lawsuit alleging that the babies were changed after birth and you are called to testify as a genetic counselor. What information would you give the jury in relation to the allegation of the couple 1?

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