Life: The Science of Biology
11th Edition
ISBN: 9781319010164
Author: David E. Sadava, David M. Hillis, H. Craig Heller, Sally D. Hacker
Publisher: W. H. Freeman
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Chapter 12.4, Problem 6R
Summary Introduction
To review:
The linked genes from the data and the distance between them in map units.
Introduction:
Linked genes are those, which get inherited together and do not follow the normal
The cross results of three autosomal characteristics in Drosophila, namely, the body color, wings shape, and eye color are as follows:
Cross I:
Parents: Heterozygous red eye color, normal wings × sepia eye color, vestigial wings.
Offspring results:
| 131 | Red-eye color, Normal wings |
| 120 | Sepia eye color, Vestigial wings |
| 122 | Red-eye color, Vestigial wings |
| 127 | Sepia eye color, Normal wings |
Cross II:
Parents: Heterozygous gray body, normal wings × black body color, vestigial wings.
Offspring results:
| 236 | Gray body, normal wings. |
| 253 | Black body, Vestigial wings. |
| 50 | Gray body, Vestigial wings. |
| 61 | Black body, Normal wings. |
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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).
. In fruit flies (Drosophila melanogaster), the bn+ allele for normal dull red eyes is dominant to the bn allele that gives brown eyes. Another gene affects wing shape; for this gene, the ct+ allele for normal wings is dominant to the ct allele, which gives “cut” wings, with jagged edges. A fly with dull red eyes and normal wings was crossed with a fly that had dull red eyes and cut wings, and the following progeny were obtained:
16 dull red eyes, normal wings
14 dull red eyes, cut wings
5 brown eyes, normal wings
5 brown eyes, cut wings
What were the genotypes of the parents?
In 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.
Chapter 12 Solutions
Life: The Science of Biology
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