BIOL 121 Study Guide - Midterm Guide: Eye Color, Wild Type, Zygosity

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BIOL 121 Full Course Notes

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Topic: determining inheritance patterns: wild-type drosophila melanogaster have dark red eyes and smooth, tapered bristles (these are the hairs that they have on their back). A geneticist performed a series of crosses using d. melanogaster with the mutant eye colour phenotype scarlet (bright red) and the mutant bristle phenotype singed (singed bristles look like they have been burned). X pure-breeding male, scarlet eyes pure-breeding female, singed bristles. Progeny (f1): 82 females, wild-type eye colour and bristles (one is used for cross 2) 79 males, wild-type eye colour and singed bristles (one is used for cross 2) Predict the outcome of a cross between a pure breeding female with scarlet eyes and a pure breeding male with singed bristles. A series of crosses between the three different types of horses produce the following progeny: Cross buckskin x buckskin bay x bay perlino x perlino buckskin x bay buckskin x perlino bay x perlino.

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Can someone please help me solve this problem, I have postedthis question twice and prof, said it was still incorrect. Pleasecan someone help me get the right answer??

Drosophila has four pairs of chromosomes: the sex chromosomes(XX in the females; XY in the males) and three pairs of autosomes.You are studying a new mutant strain with blue eyes. You wish toknow if blue eye colour is a dominant mutation and on whichchromosome the blue eye locus can be found. When you cross apureâbreeding female blueâeyed fly with vestigial wings andspineless bristles to a male fly with wild type eye colour, wings,and bristles, all of the F1 progeny are completely wild type. An F1male is backcrossed to a triple mutant female, producing thefollowing progeny (remember that there is no crossing over inDrosophila males):

Wild type eyes, wings, and bristles: 72 females, 69 males

Wild type eyes and bristles, vestigial: 83 females, 77 males

Wild type wings, blue eyes, spineless: 60 females, 65 males

Blue eyes, spineless, vestigial: 62 females, 58 males

1- Is the mutation dominant or recessive?Explain.

2-Since you know that the locus for vestigial wings is onchromosome 2 and the locus for spineless bristles is on chromosome3, what chromosome carries the locus for blue eyes? Show your work,including the stepâbyâstep reasoning you used to arrive at youranswer.

3-When an F1 female is backcrossed to a triple mutant male, thefollowing 1,000 progeny are produced:

Wild type eyes, wings, and bristles: 90 females, 89 males

Wild type eyes and bristles, vestigial: 83 females, 98 males

Wild type eyes and wings, spineless: 37 females, 35 males

Wild type wings and bristles, blue eyes: 36 females, 34males

Wild type wings, blue eyes, spineless: 92 females, 88 males

Wild type eyes, spineless, vestigial: 34 females, 39 males

Wild type bristles, vestigial, blue eyes: 33 females, 37males

Blue eyes, spineless, vestigial: 90 females, 85 males

4-Calculate the map distance between blue eye and any linkedgenes from the above progeny. Show your work

coffeewhale367

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

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?

BIOL 121 Study Guide - Midterm Guide: Eye Color, Wild Type, Zygosity

BIOL 121 Full Course Notes

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