In Drosophila, allelic series of gene w+ determine the color of an eye. w+ determines red color (wild type), w^e determines eosin color and w^a â apricot color. The allelic realtions are w+ > w^e > w^a > w. The gene is sex-linked.

A female fly with eosin eyes was crossed with a male fly with apricot eyes. Write down the cross showing the genotypes for P. F1, F2 and a ratio observed in F2.

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Nestor RutherfordLv2

28 Aug 2018

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You are given 4 true-breeding mutant strains of fruit flies, each with a different eye colour
phenotype (apricot, orange, brown & scarlet). Specific reciprocal crosses between the recessive
mutant strains produced the following results in the F1 generations:
P1: apricot female x orange male F1 : apricot males and orange females
P1: orange female x apricot male F1 : orange males and females
P1: brown female x scarlet male F1 : wildtype males and females
P1: scarlet female x brown male F1 : wildtype males and females

i) Are the four mutant phenotypes all controlled by different alleles of a single gene? Explain.

ii) Which of the mutant phenotypes, if any, are due to allelic mutations?

iii) Which of the mutant phenotypes, if any, are due to alleles of autosomal genes? Explain.

iv) Using your own symbols for the mutations, indicate the genotypes of the F1 generation males
and females in each of the crosses.

v) Which of the F1 generations when intercrossed are likely to yield recombinant phenotypes in
the F2 generations? Explain showing the expected phenotypes and their proportions. (You
may assume that Mendelâs 2nd Law of Heredity holds true for the mutations involved in this
situation. Further assume that the double mutant results in a white eye color).

vi) Predict the outcome in the F1 generations of a reciprocal cross between a truebreeding strain
with brown eyes and another with apricot eyes.

1. The eye color of wild-type Drosophila flies is red. Differentmutations in a single or in multiple genes lead to flies with whiteeyes. Mutations in the w gene on the X chromosome lead to whiteeyes instead of the normal red. You have isolated both a white-eyedmutation (designated W-1) that gives a dominant phenotype, and awhite-eyed mutation (designated w-2) that gives a recessivephenotype.

(a) A white-eyed male from the W-1 line is crossed to awild-type female. What color eyes will the female progeny from thiscross have?

(b) What color eyes will the male progeny from the cross in part(a) have?

(c) One of the female progeny from the cross in part (a) ismated to a white-eyed male from the w- 2 line. What fraction of thewhite-eyed progeny from this cross will be female?

2. The body color of Drosophila adult flies is regulated bymultiple genes, including the autosomal ebony gene. Ebony body (e)is recessive to the wild type (yellowish) body (e+). A second gene,which is X-linked, controls bristle shape. Normal bristle shape(f+) is dominant to the mutant forked bristles (f). A female withforked bristles that is heterozygous for the body color gene ismated with an ebony body male (his bristles are normal).

(a) What are the genotypes of the parents?

(b) Using a Punnett square, determine the expected proportionsof each possible progeny phenotype. Since there is a sex-linkedgene here, be sure to include consider sex as part of thephenotype.

3. Describe in your own words what a balancer chromosome is andwhy it is important in fly genetics (you will have to do someresearch for this one!)

mauvepug893

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?