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Calvin Bridges’s classic study of nondisjunction of sex chromosomes provided support for the chromosome theory of inheritance. Bridges performed crosses with fruit flies, tracking the sex-linked eye-color trait. Red-eyed males were crossed with white-eyed females. Which of the following is an accurate explanation of his findings?

a. The offspring were mostly white-eyed females and red-eyed males, but 1/ 2,000 offspring were white-eyed females (genotype XX) or red-eyed males (genotype XY).

b. The offspring were mostly white-eyed males and red-eyed females, but 1/ 2,000 offspring were white-eyed females (genotype XXY) or red-eyed males (genotype XO).

c. The offspring were mostly white-eyed females and red-eyed males, but 1/ 2,000 offspring were white-eyed females (genotype XXY) or red-eyed males (genotype XO).

d. The offspring were mostly white-eyed males and red-eyed females, but 1/ 2,000 offspring were white-eyed females (genotype XX) or red-eyed males (genotype XO).

e. The offspring were mostly white-eyed males and red-eyed females, but 1/ 2,000 offspring were white-eyed females (genotype XXX) or red-eyed males (genotype XY).

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Jean Keeling
Jean KeelingLv2
28 Sep 2019
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Related questions

1.A homozygous red-eyed female Drosophilamates with a red-eyed male Drosophila. What proportion of thefemale offspring will have white eyes?
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100%
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2.Red-green colorblindness is a recessive X-linked trait.If a female is red-green colorblind, which of the following isTRUE?
Her father mustbe colorblind.
Both herparents are carriers of the recessive allele.
Both herparents must be colorblind.
Her mother mustbe colorblind.
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3.Allelesare
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4.Using three bases torepresent each amino acid in a polypeptide
ensures that other organisms can read the codetoo.
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6. Atrue-breeding tall pea plant is crossed with a tall pea plant ofunknown parentage. Which of the following iscorrect?
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12.Which of the following is TRUE?
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Females can beheterozygous for sex-linked traits.
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Answer withBRIEF EXPLANATIONS please
if more than 2answers you given are wrong, low star, pretty much no pts!

Please assist with the following. Please no hand-written work, but typed work and thorough explanations please including Punnett Squares. Please Ignore Sex, as these are not sex-linked traits

Dihybrid Testcrosses

In the following crosses, the wild trait is dominant and the brown trait for eye color and ebony trait for body color are both recessive. You will compare the offspring of homozygous wild flies to the offspring of heterozygous wild flies, when each is crossed with a recessive brown-eyed fly with an ebony body.

7. Perform a monohybrid cross between a wild-type female fly and a male fly with brown eyes and ebony body.
Show results for the F1 offspring. (NOTE: You will use one of these F1 flies in the next cross.)
ENTER DATA HERE:

PUNNETT SQUARE:

List the genotypes of the flies in this cross:

List the gametes produced by each fly in this cross:

Show the Punnett Square for the above cross.

Question: By examining the offspring, determine whether the wild-type female parent was homozygous or heterozygous for eye color and body color. How did you arrive at this conclusion?

Question: Are the F1 offspring homozygous or heterozygous for eye color and body color? How did you arrive at this conclusion?

8. Now perform a cross between one wild-type F1 offspring from the previous cross and a male fly with brown eyes and ebony body.
ENTER DATA HERE:

PUNNETT SQUARE:

List the genotypes of the flies in this cross:

List the gametes produced by each fly in this cross:

Show the Punnett Square for the above cross.

Question: Even though you already knew the genotype of the wild-type fly used in this cross, how can you tell by examining the offspring of this cross whether the wild-type fly in this cross was homozygous or heterozygous for eye color?

Question: What was the phenotypic ratio for the offspring resulting from this testcross?

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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