If two genes on the same chromosome exhibit complete linkage, what is the expected F2 phenotypic ratio from a selfed heterozygote with the genotype a + b + ⁄⁄ ab?

From a cross between individuals with the genotypes Cc Dd Ee × cc dd ee, 1000 offspring were produced. The class that was C- D- ee included 351 individuals. Are the genes c, d, and e on the same or different chromosomes? Explain.

Assume that the length of a type of cucumber at maturity is controlled by two genes (A and B), each of which has two alleles. The A and B alleles each add 3 inches of cucumber growth, while the a and b alleles add only 1 inches. If a plant with genotype Aabb is crossed to a plant with genotype AaBb, what ratios of lengths are expected in the progeny?     1/8-12”, 3/8-10”, 3/8-8”, 1/8-6”     1/2-8”, 3/8-6”, 1/8 4”     1/8-10”, 3/8-8”, 3/8-6”, 1/8-4”     1/2-12”, 3/8-10”, 1/8 8”     1/2-10”, 3/8-8”, 1/8 6”

If genes A and B are linked, how would you figure out what would be the expected percentages of nonrecombinant and recombinant progeny in a test cross of AaBb heterozygotes?

Three enzymes are part of a sequential pathway that produces a pigment that makes flowers red.  Each enzyme is the gene product of a different locus. If a trihybrid, heterozygous (+/-) for each of the three loci, is selfed, what fraction of the offspring will not be able to produce the red pigment (and will thus have white flowers)? Express your answer as a number between 0 and 1, rounding to 2 decimal places.  For example, if you think 1/4 of the offspring will have white flowers, then answer 0.25

What is the predicted phenotypic outcome of a dihybrid cross and a dihybrid text cross? Why?

L, R, P and D are four genes located on the same chromosome in a diploid organism. Map distances between different pairs of genes were determined and the following results obtained. Based on these data, what is the order of the genes on the chromosome? D-R: 35 CM P-D: 5 CM L-R: 10 CM D-P: 30 CM D-L 25 CM P-R: 40 CM Note that only one orientation of the order is given as an answer choice. For example: ABCD has the same order as DCBA, but only ABCD would be listed as a possible answer. So be sure to check both orientations when comparing your gene order to the possible answer choices. D-L-P-R P-D-L-R P-R-D-L L-P-R-D R-L-D-P

The alleles his-5 and lys-1, found in yeast, result in cells that require histidine and lysine for growth, respectively.  A cross was made between two haploid yeast strains that are his-5 lys-1 and his+ lys+.  973 tetrads were analyzed, with the follow pattern:   7 tetrads with 2 his-5 lys+ spores and 2 his+ lys-1 spores 603 tetrads with 2 his-5 lys-1 spores and 2 his+ lys+ spores 363 tetrads with 1 his-5 lys-1 spore, 1 his-5 lys+ spore, 1 his+ lys-1 spores, and 1 his+ lys+ spore   Compute the map distance between these two genes using the method that considered double crossovers and the one that does not.  Show your work.  Which give the higher value?  Why?   What is the frequency of single crossovers between these genes?  Explain.   Based on the frequency of single-crossovers, how many double crossovers would one expect?  Is positive interference occurring?

The radish (Raphanus sativus) has a diploid number (2n) of 18. The cabbage (Brassica oleracia) also has a diploid number (2n) of 18. Why is it that if you cross these two species to produce a hybrid with a total of 18 chromosomes in its somatic cells it is sterile, but if you form an allotetraploid (also known as amphidiploid) from these two species it is fertile?

A 2n=4 plant is heterozygous at two genes, one controlling plant height (T = tall, t= short) and one controlling disease resistance (D = resistant, d = susceptible). The plant height gene is located on one chromosome, and the disease resistance gene is located on the other chromosome. In the cells below, draw to two possible arrangements of the chromosomes at metaphse I of meiosis. Hint: look at Figure 2.17 in your textbook for an example of how chromosomes can be arranged at metaphase I. Be sure to label the alleles present at the genes on the two chromosomes in each drawing. 00