Concept explainers
In Drosophila, the autosomal recessive brown eye color mutation displays interactions with both the X-linked recessive vermilion mutation and the autosomal recessive scarlet mutation. Flies homozygous for brown and simultaneously hemizygous or homozygous for vermilion have white eyes. Flies simultaneously homozygous for both the brown and scarlet mutations also have white eyes. Predict the F1 and F2 progeny of crossing the following true-breeding parents:
a. vermilion females × brown males
b. brown females × vermilion males
c. scarlet females × brown males
d. brown females × scarlet males
To determine:
The F1 and F2 progeny from the cross between vermilion females and brown males
Introduction:
The genes are the sequence of nucleotides that are present on the chromosomes and encode for a specific protein that plays a crucial role in the functioning of the different processes in an organism. The gene is located at specific gene loci and can be structural or regulatory in nature.
Explanation of Solution
The allele for vermillion trait can be expressed as (XVXV) and the allele for brown trait is (EbEb). The F1 progeny from cross between vermilion females and brown males will be as follows:
Gametes | XV | XV |
Eb | XV Eb | XV Eb |
Eb | XV Eb | XV Eb |
The F2 progeny will be as follows:
Gametes | XV | Eb |
XV | XV XV | XV Eb |
Eb | XV Eb | Xb Eb |
To determine:
The F1 and F2 progeny from the cross between brown females and vermilion males
Introduction:
The genotype is the genetic constitution of the organism while the phenotype is the external characters visible in an organism. The alleles are the contrasting forms of a gene and one of them is dominant and other is recessive
Explanation of Solution
The vermillion males can be expressed as (XVY) and the brown females can be expressed as (Eb Eb). The progeny from the cross of vermilion males and brown females will be as follows:
Gametes | Eb | Eb |
XV | XV Eb | XV Xb |
Y | Eb Y | Eb Y |
The progeny obtained from the F2 cross will be
Gametes | Eb | Y |
XV | XV Eb | XVY |
Eb | Eb Eb | Eb Y |
To determine:
The F1 and F2 progeny from the cross between brown females and vermilion males
Introduction:
The dominant allele masks the expression of the recessive allele. Therefore the dominant allele is expressed in homozygous and heterozygous genotype while the recessive phenotype is only expressed under homozygous condition.
Explanation of Solution
The scarlet females can be expressed through alleles (ESES) and the brown males are expressed as (EbEb). The progeny from the cross of brown males and scarlet females will be as follows:
Gametes | Eb | Eb |
Es | Eb Es | Eb Es |
Es | Eb Es | Eb Es |
The progeny obtained from the F2 cross will be
Gametes | Es | Eb |
Eb | Eb Es | Eb Eb |
Es | Es Es | Eb Es |
To determine:
The F1 and F2 progeny from the cross between brown females and scarlet males
Introduction:
Fertilization is the process by which the male gamete, sperm, fertilize with the female gamete, ovary. The process brings about the fusion of two haploid pronuclei into a diploid zygote.
Explanation of Solution
The brown females can be seen as (EbEb) and scarlet males are represented as (ESES). The progeny from the cross of brown females and scarlet males will be as follows:
Gametes | Eb | Eb |
Es | Eb Es | Eb Es |
Es | Eb Es | Eb Es |
The progeny obtained from the F2 cross will be
Gametes | Es | Eb |
Eb | Eb Es | Eb Eb |
Es | Es Es | Eb Es |
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Chapter 4 Solutions
Genetics: From Genes to Genomes
- The recessive, X-linked z1mutation of the Drosophilagene zeste (z) can produce a yellow (zeste) eye coloronly in flies that have two or more copies of the wildtype white (w) gene. Using this property, tandem duplications of the w+ gene called w+Rwere identified.Males with the genotype y+ z1w+R spl+ / Y thus havezeste eyes. These males were crossed to females withthe genotype y z1 w+R spl / y+ z1 w+R spl+. (These fourgenes are closely linked on the X chromosome, in theorder given in the genotype, with the centromere tothe right of all these genes: y = yellow bodies; y+ =tan bodies; spl = split bristles; spl+ = normal bristles.) Out of 81,540 male progeny of these females,the following exceptions were found:Class A 2430 yellow bodies, zeste eyes, wild-type bristlesClass B 2394 tan bodies, zeste eyes, split bristlesClass C 23 yellow bodies, wild-type eyes, wild-type bristlesClass D 22 tan bodies, wild-type eyes, split bristlesa. What were the phenotypes of the remainder of the81,540 males…arrow_forwardMiniature wings (Xm) in Drosophila result from an X-linked allele that is recessive to the allele for long wings (X*). Give the genotypes of the parents in the following cross: Male parent Female parent Male offspring Female offspring Long Miniature 750 miniature 761 long O male: X* / X* and female X™ /x+ O male: X*/Xt and female Xm /xm O male: X*/ Y and female Xm /xm O male: Xm/ Y and female Xm /xmarrow_forwardIn Drosophila melanogaster, white eyes (w) is an X-linked recessive mutation. Normal eyes are red (W). At the autosomal wing shape locus, normal shaped wings (Vg) are dominant to vestigial wings (vg). The following cross was made: XWXW Vgvg x XWY Vgvg What proportion of the progeny from this cross will be males with white eyes and normal wings? Write your answer as a numerical value rounded properly to 4 decimal digits. Do not write the answer as a fraction or percentage.arrow_forward
- In Drosophila fruit flies, the genes for warped wings (dwp), rumpled bristles (rmp), and pallid wings (pld) are linked. A trihybrid female for all three allleles is crossed with homozygous recessive male for all three alleles and the offspring obtained showed the following phenotypes: 3 pld rmp dwp 428 pld rmp + 427 + + dwp 48 + rmp + 47 pld + dwp 23 pld + + 2 + + + 22 + rmp dwp What is the order and map distance between these three alleles?arrow_forwardIn Drosophila, the autosomal recessive brown eye color mutation displays interactions with the X-linked recessivevermilion mutation. Flies homozygous for brown and hemizygous or homozygous for vermilion have white eyes.Predict the F1 and F2 progeny of crossing these true-breeding parents: brown females and vermilion males.arrow_forwardConsider the following three autosomal recessive mutations in Drosophila:vestigial wings (v); wild type is long (v+)black body color (b); wildtype is gray (b+)plum eyes (p); wildtype is red (p+)A vestigal, gray, red female (homozygous for all three genes) is crossed with a long wing, black, plum male (homozygous for all three genes). The F1 female progeny are mated with triple homozygous recessive males. Here is the phenotypic data for the F2 progeny:vestigal; gray; red 580long wings; black; plum 592vestigal; black; red 45long; gray; plum 40vestigal; black; plum 89long; gray; red 94vestigal; gray; plum 3long; black; red 5A total of 1448 progeny were counted.Which one of the following values is the approximate distance between the plum eye color and black body color loci?arrow_forward
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