Concept explainers
To review:
The
Introduction:
When the genes are present on X-chromosomes, it is known as X-linked trait. The example can be seen in Drosophila, where the genes for colored eyes are present on the X-chromosome. The red-colored eye is dominant in Drosophila over the white-colored eye.
Explanation of Solution
Genes for colored eyes in Drosophila are present on the X-chromosome. The white-colored eyes is an X-linked recessive trait found in Drosophila. The red-colored eyes are dominant in them.
Let
The cross can be made as:
Parents
Gametes
Gametes | |||
F1 female progeny is crossed with her father:
The cross can be made as:
Parents
Gametes
F1 progeny
Gametes | ||
So, the ratio of female progenies, red to white is 2:0 and for male progenies, red to white is 1:1.
Now,
The cross can be made as follows:
Parents
Gametes
Gametes | ||
Therefore, the ratio of red to white female progenies is
Thus, it can be concluded that when the F1 female progeny is crossed with her father, the ratio of female progenies, red to white, is 2:0, whereas, for male progenies, the ratio of red to white is 1:1. When the F1 male progeny is crossed with his mother, the ratio of female progenies, red to white, is 0:2, whereas, for male progenies, the ratio of red to white is 0:2.
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Chapter 13 Solutions
Biology: The Dynamic Science (MindTap Course List)
- In Drosophila, a cross was made between a yellow-bodied male with vestigial wings and a wild-type (WT) female(brown body and normal wings). The F1 generation consisted of WT males and WT females. The F1 males and females were crossed, and the F2 progeny consisted of 16 yellow males with vestigial wings, 48 yellow males with WT wings, 15 brown males with vestigial wings, 49 WT males, 31 brown females with vestigial wings, and 97 WT females. Based on these results, explain the inheritance of the two genes (i.e. autosomal or sex-linked, dominant or recessive).arrow_forwardAnother cross in Drosophila involved the recessive, X-linked genes yellow (y), white (w) and cut (ct). A yellow-bodied, white-eyed female with normal wings was crossed to a male whose eyes and body were normal but whose wings were cut. The F1 females were wild type for all three traits, while the F1 males expressed the yellow-body and white eyes traits. The cross was carried to an F2 progeny and only male offspring were tallied. Based on the data shown here, a genetic map was constructed. a) Diagram the genotypes of the F1 parents. b) Construct a map, assuming the white is at locus 1.5 on the X-chromosome. Phenotype Male offspring y + ct 9 + w + 6 y w ct 90 + + + 95 + + ct 424 y w + 376 y + + 0 + w ct 0arrow_forwardA mutant sex-linked trait called “notched” (N) is deadly in Drosophila when homozygous in females. Males who have a single N allele will also die. The heterozygous condition (Nn) causes small notches on the wing. The normal condition in both male and females is represented by the allele n. a) Indicate the phenotypes of the F1 generation from the following cross: XNXn x XnY b) Explain why dead females are never found in the F1 generation no matter which parents are crossed. c) Explain why the mating of female XNXn and a male XNy is unlikely.arrow_forward
- Another cross in Drosophila involved the recessive, X-linked genes yellow (y), white (w) and cut (ct). A yellow-bodied, white-eyed female with normal wings was crossed to a male whose eyes and body were normal but whose wings were cut. The F1 females were wild type for all three traits, while the F1 males expressed the yellow-body and white eyes traits. The cross was carried to an F2 progeny and only male offspring were tallied. Based on the data shown here, a genetic map was constructed. a) Diagram the genotypes of the F1 parents. b) Construct a map, assuming the white is at locus 1.5 on the X-chromosome *******ANSWER PART B NOT PART A!!!! Phenotype Male offspring y + ct 9 + w + 6 y w ct 90 + + + 95 + + ct 424 y w + 376 y + + 0 + w ct 0arrow_forwardIn Drosophila, white eyes (w) are recessive to red eyes (w+) at one locus and black body (b) is recessive to gray body (b+). A homozygous white eyes, gray bodied female is crossed with a homozygous red eyes, black bodied male to produce the F1 progeny. The F1 progeny are testcrossed and produce the following progeny: White eyes, black body: 212 White eyes, gray body: 288 Red eyes, black body: 308 Red eyes, gray body: 192 Does the evidence indicate that w and b loci are linked? Explain why or why not? If they are linked, what is the map distance between the two loci? If they are not linked, what is the map distance between the two loci? If they are linked, are the allels in the F1 in coupling or repulsion? How do you know? Draw the genotypes of all individuals described in the problem (original parents, F1, testcross, and F2 progeny) using the appropriate notation.arrow_forwardIn fruit flies, the following X-linked traits are found: white eyes are recessive to red eyes, ebony body is recessive to gray body, and short wings is recessive to long wings. A cross was made between wild-type males with red eyes, long wings, and gray bodies and females with white eyes, short wings, and ebony bodies. Female heterozygote resulting from this cross, which had red eyes, long wings, and gray bodies, were then crossed with males with white eyes, short wings, and ebony bodies. The F2 generation data is obtained below: 1299 white eyes, short wings, ebony bodies 1367 red eyes, long wings, gray bodies 99 white eyes, short wings, gray body 89 red eyes, long wings, ebony bodies 49 white eyes, long wings, ebony bodies 49 red eyes, short wings, gray bodies 1 red eyes, short wings, ebony bodies 1 white eyes, long wings, gray bodies A) Calculate the map distance separating the three genes B) Which gene is in the middle?arrow_forward
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- A recessive allele causes Drosophila to have white eyes instead of wild-type eyes. This eye colourgene is known to be X-linked. In a cross between homozygous wild-type females and white-eyedmales, all F1 progeny have wild-type eyes. What ratio of wild-type to white-eyed progeny can be expected in each sex if F1 females arecrossed to males of the same genotype as their father?a. Males – 1 : 0; females – 1 : 0b. Males – 1 : 1; females – 1 : 0c. Males – 0 : 1; females – 1 : 1d. Males – 1 : 1; females – 1 : 1arrow_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, the sepia mutation (se, chromosome 3, position 26) results in dark brown eyes, while cinnabar (cn, chromosome 2, position 57.5) results in bright orange-red eyes. True breeding, wild type females are mated with true breeding males homozygous recessive for both traits. Using Drosophila notation, diagram the P1 and F1 crosses. P1 F1 Fill in the chart with phenotypic ratios that would be expected in the F2 generation. Use the space provided to show your work. Phenotype Females Males Overall (♀and ♂) =1 =1arrow_forward
- Human Biology (MindTap Course List)BiologyISBN:9781305112100Author:Cecie Starr, Beverly McMillanPublisher:Cengage Learning