Concept explainers
Genes A, B, C, D, and E are linked on a chromosomeand occur in the order given. The test cross
a. If
b. Previous genetic linkage crosses have determined that recombination frequencies for these genes are
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GENETIC ANALYSIS: INTEGRATED - ACCESS
- In autotetraploid Chinese primrose (Primula sinensis L.), the gene controlling stigma color is very near the centromere of the chromosome carrying it. The allele G for green stigma is dominant to g for red stigmas. A homozygous green autotetraploid strain is crossed with a homozygous red autotetraploid strain. Show the types of gametes the F1’s may be expected to form and derive the expected proportion of each.arrow_forwardIn an autotetraploid Chinese primrose (Primula sinensis L.), the gene controlling stigma color is very near the centromere of the chromosome carrying it. The allele G for green stigma is dominant to g for red stigmas. A homozygous green autotetraploid strain is crossed with a homozygous red autotetraploid strain. What is the genotype of the F1? Show the types of gametes the F1’s may be expected to form and derive the expected proportion of each. What phenotypic ratio of green to red is expected if: The F1’s are intercrossed? The F1’s are crossed with red plants If the G locus were 50 or more map units from the centromere, what types and proportions of gametes would the F1 be expected to produce? Derive the expected F2 phenotypic ratio.arrow_forward+ ec +/Y + + w/Y y ec +/Y + ec +/y ec w ++ w/y ec w у ес +у ес и Determine the order in which the three loci y, ec, and w Occur on the chromosome and prepare a linkage map. 7.22 A cross involving X-linked genes was made between yellow, bar, vermilion female fies and wild males, and the F1 females were crossed with y B v males. The following phenotypes were obtained when 1000 progeny were exam- ined: Dra ord ma the 7.2 546 244 160 50 + + + + Bv y Bv y+ + y+v y B+ and an and and and +B + re + + v ge Determine the order in which the three loci occur on the chromosome and prepare a linkage map. 7.23 Female Drosophila heterozygous for ebony (e"le), scarlet (st*/st), and spineless (ss*/ss) were testcrossed, and the following progeny were obtained: PROGENCY PHENOTYPES NUMBER ir Wild type Ebony Ebony, scarlet Ebony, spineless Ebony, scarlet, spineless Scarlet 67 8. 68 347 78 368 Scarlet, spineless Spineless (a) Are these genes linked? Justify your answer. (b) Write the genes given on a…arrow_forward
- In com, male sterility is controlled by maternal cytoplasmic elements. However, the presence of a nuclear fertility restorer gene (F_) restores fertility to male sterile lines. a. What are the crosses male sterile female x FF male? Give the genotypes and phenotypes of the offspring in each cross. Explain.arrow_forwardDeduce the phenotypic proportions in the progeny of thefollowing crosses of autotetraploids in which the a+/a locus is very close to the centromere. (Assume that the fourhomologous chromosomes of any one type pair randomly two by two and that only one copy of the a+ allele isnecessary for the wild-type phenotype.)a. a+/a+/a/a × a/a/a /ab. a+/a/a /a × a/a/a/ac. a+/a/a /a × a+/a/a /ad. a+/a+/a /a × a+/a/a /aarrow_forwardAssume that there is complete interference in the Lf-W region. The cross between the triple heterozygote (Lf J W/ lf j w) and a triple homozygous recessive produced 350 progenies. Give the frequency of each specific progeny type:a. with crossover in the Lf-J and J-W regionsb. with crossover in the Lf-J regionc. with crossover in the J-W regiond. without crossover in the Lf-W regionarrow_forward
- In a fungus with four ascospores, a mutant allele lys-5causes the ascospores bearing that allele to be white,whereas the wild-type allele lys-5+ results in black ascospores. (Ascospores are the spores that constitute thefour products of meiosis.) Draw an ascus from each ofthe following crosses:a. lys-5 × lys-5+b. lys-5 × lys-5c. lys-5+ × lys-5+arrow_forwardIn autotetraploid Chinese primrose (Primula sinensis L.), the gene controlling stigma color is very near the centromere of the chromosome carrying it. The allele G for green stigma is dominant to g for red stigmas. A homozygous green autotetraploid strain is crossed with a homozygous red autotetraploid strain. Each of the F1 GGgg plants would obtain 12 gametes which are 2GG, 8Gg, and 2g. How were these obtained?arrow_forwardn corn, male sterility is controlled by maternal cytoplasmic elements. This phenotype renders the male part of the corn plants (i.e the tassel) unable to produce fertile pollen; the female parts, however, remain receptive to pollination by pollen from male fertile corn plants. However, the presence of a nuclear fertility restorer gene F restores fertility to male sterile lines Using the cardboard chips, simulate the crosses indicated below. Give the genotypes and phenotypes of the offsprings in each cross, and properly label the nucleus and the cytoplasm each individual in the cross Legend male sterile cytoplasm Male fertile cytoplasm FF nucleus Ff nucleus ff nucleus A. Male sterile female x FF male Explain the phenotype of the offspring B. Male sterile female x Ff male Explain the phenotype of the offspringarrow_forward
- b) You test cross an F1 fish (with genotype BbCc) and obtain 1000 offsprings in F2 generation with the following results: 474 Bbcc, 480 bbCc, 20 BbCc and 26 bbcc.1. Create and fill in a Punnet square for this cross.2. What type of cross is it? 3. Are these loci linked? 4. What are the two parental classes and the two recombinant classes of offspring? 5. What is the percentage of recombination between these two loci? Show your calculations. 6. How many map units apart are they?arrow_forwardIn autotetraploid Chinese primrose (Primula sinensis L.), the gene controlling stigma color is very near the centromere of the chromosome carrying it. The allele G for green stigma is dominant to g for red stigmas. A homozygous green autotetraploid strain is crossed with a homozygous red autotetraploid strain. 1. What is the genotype of the Fl? 2. Show the types of gametes the Fl's may be expected to form and derive the expected proportion of each. Show your solution. 3. What phenotypic ratio of green to red is expected if: a. the Fl's are intercrossed? Show your solution. b. the Fl's are crossed with red plants? Show your solution. c. If the G locus were 50 or more map units from the centromere, what types and proportions of gametes would the Fl be expected to produce? Derive the expected F2 phenotypic ratio.arrow_forwardshows the results of a dihybrid cross involving seed shape and seed color. a. What proportion of the round and yellow F2 progeny from this cross is homozygous at both loci? b. What proportion of the round and yellow F2 progeny from this cross is homozygous at least at one locus?arrow_forward
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