In fruit flies, the autosomal recessive mutation pr causes brown eyes whereas the cn mutation causes bright-red eyes (again autosomal recessive). When both mutations are homozygous in the individual (double mutant; pr-cn combination), it causes orange eyes. Wild-type flies have red eyes. It is known that these genes are found on the same chromosome.

In Drosophila, a cross (cross 1) was made between twomutant flies, one homozygous for the recessive mutationbent wing (b) and the other homozygous for the recessivemutation eyeless (e). The mutations e and b are alleles oftwo different genes that are known to be very closelylinked on the tiny autosomal chromosome 4. All the progeny had a wild-type phenotype. One of the female progeny was crossed with a male of genotype b e/b e ; we willcall this cross 2. Most of the progeny of cross 2 were of theexpected types, but there was also one rare female ofwild-type phenotype.a. Explain what the common progeny are expected tobe from cross 2.b. Could the rare wild-type female have arisen by (1)crossing over or (2) nondisjunction? Explain.

Drosophila can have a yellow-brown body (wild-type [+]) or a black body [b] as a result of a mutation in the black gene (marked b). a mutation in the black gene (marked b). There is also a mutation in the purple gene (marked pr) which purple eyes (mutant phenotype [pr]). Flies with normal eyes are noted [+]. a/ Pure strains of male Drosophila [b] are crossed with female Drosophila [pr] (1st cross). The F1 progeny contains only wild-type Drosophila for the two [+, +] traits. both [+, +] traits. The reciprocal cross gives the same result. What information can you draw from this?

In Drosophila, females heterozygous for the recessive alleles c, d, and e were crossed to males homozygous recessive for these three mutant genes.  The phenotypes of the resulting progeny were:           cd+            350        ++e            350          c + e          51        + d +          49           c + +         100        + d e         100      _________     _____     Total progeny   1000 How were the three pairs of alleles arranged in the heterozygous females?   a. +d+/c+e   B. cde/+++   C. +de/c++   D. cd+/++e

In the fruit fly, dumpy wings (d) and purple eyes (p) are encoded by mutant alleles that are recessive to those that produce wild type traits; long wings (d+) and red eyes (p+). These two genes are on the same chromosome. In a particular lab, two researchers Walt and Jesse crossed a fly homozygous for dumpy wings and purple eyes with a fly homozygous for the wild type traits. The F1 progeny, which had long wings and red eyes, was then crossed with flies that had dumpy wings and purple eyes. Unfortunately, the progeny of this cross somehow escaped. To prevent their other projects from contamination, they decided to spend an exceptionally boring hour in the lab catching and counting the progeny and found the following:   long wings, red eyes – 482 dumpy wings, purple eyes – 473 long wings, purple eyes – 23 dumpy wings, red eyes - 22   What is the genetic distance between these two loci? a. 4.5 cM b. 55 cM c. 45 cM d. 49.5 cM  e. 4.7 cM

In Drosophila, the genes st (scarlet eyes), ss (spineless bris- tles), and e (ebony body) are located on chromosome 3, with map positions as indicated: st SS e 44 58 70 Each of these mutations is recessive to its wild-type allele (st*, dark red eyes; ss*, smooth bristles; e*, gray body). Phenotypically wild-type females with the genotype st ss e*/st* st* ss+ e were crossed with triply recessive males. Predict the phenotypes of the progeny and the frequen- cies with which they will occur assuming (a) no interfer- ence and (b) complete interference.

A defective gene on chromosome 15 causes Tay-Sachs disease. It is a central nervous system neurodegenerative disease that most often affects infants, though older children and adults can have late-onset forms of the disease. The defective gene prevents the body from making a protein called hexosaminidase A. Without, hexosaminidase A, chemicals called gangliosides build up in the nerve cells of the brain, destroying brain cells. Pedigree information regarding the incidence of Tay-Sachs within a family is depicted above. The row below that indicates the genotypes of individuals II-1, II-2, and III-1 is Select one: a. II-1 II-2 III-1 Aa Aa aa b. II-1 II-2 III-1 XAY XAXa XAXa c. II-1 II-2 III-1 XAY XAXA XaXa d. II-1 II-2 III-1 AA aa Aa

There are two genetic disorders that result from mutation in imprinted genes: Prader-Willi syndrome, Angelman syndrome.  Angelman syndrome results from deletion of UBE3A, which is a gene imprinted such that only the maternal copy is expressed. In the pedigree above, individual I-1 is heterozygous for a deletion of UBE3A and does not have Angelman syndrome.  Individual I-2 is homozygous wild type for UBE3A.  Which individuals in the pedigree are at risk for exhibiting Angelman syndrome, if any?  (Who could potentially have the syndrome, based on what alleles it is possible for them to inherit and express?)   Question 8 options:   Only I-1 could have been at risk.  If he does not have the syndrome, no one in the pedigree could.   Only III-1 is at risk   I-1, II-2, and III-1 are all at risk   Only II-2 is at risk   No one in the pedigree is at risk   Both II-2 and III-1 are at…

Suppose researchers identified two Drosophila melanogaster mutant phenotypes. One phenotype is called maniac and the other is called shiny. In order to determine the mode of inheritance of the mutant allele responsible for each phenotype, males that have both mutant phenotypes are mated with wild-type (wt) females to produce F₁ progeny. Then, the F₁ progeny are mated together and the F2 progeny are scored. F₁ phenotypic class maniac male maniac female n 481 478 autosomal dominant for maniac and X-linked dominant for shiny autosomal recessive for maniac and autosomal recessive for shiny autosomal dominant for maniac and X-linked recessive for shiny X-linked dominant for maniac and X-linked recessive for shiny What is the genotype of the original male parent? F2 phenotypic class maniac female maniac male What is the mode of inheritance for the genes controlling maniac and shiny? maniac, shiny male shiny male wt female wt male homozygous mutant at both loci heterozygous mutant at one…

Males of many diploid species (like us) have X and Y sex chromosomes. They are hemizygous for most X- linked genes. Thus, males express most X-linked alleles, whether they are dominant or recessive in females. In the fruit fly Drosophila, it is common to achieve the equivalent of a test cross of X-linked genes in females by assessing the readily observed phenotypes of their male progeny. Since males do not receive X-linked genes from their father, sires of these crosses can be normal or wild-type flies. In fly genetics, it is conventional to name a gene after the mutant phenotype that enabled its discovery. Your challenge is to establish gene order and map distances between three X-linked genes in Drosophila. Each gene is represented by recessive mutant alleles that express rather distinctive phenotypes relative to their dominant wild-type alternative alleles. Flies expressing fruitless (f) are bisexual, lush (1) have a heightened responses to ethanol, and ken&barbie (kb) lack external…