In the fruit fly Drosophila, there is a dominant gene for normal wings and its recessive allele for vestigial wings. At another gene locus on the same chromosome, there is a dominant gene for red eyes and its recessive allele for purple eyes. A male that was heterozygous at both gene loci was mated with a female that was homozygous for both recessive alleles and the following results were observed among the offspring:Normal wings and red eyes - 420Vestigial wings and red eyes - 80Normal wings and purple eyes - 70Vestigial wings and purple eyes - 430According to these data, what is the distance, in centimorgans, between these 2 gene loci? (Enter the number only without the units. For example, 100 cM would be entered as 100)
Fill in the blank(s) with the appropriate word(s).
15
Clarify Question
• What is the key concept addressed by the question?
o This question addresses linkage mapping by recombination.
• What type of thinking is required?
o Although you may not have seen this example before, you know enough about the concept to Apply your knowledge and understanding to this unfamiliar situation.
• What key words does the question contain?
o Dominant alleles are expressed in the heterozygote; recessive alleles are only expressed in the homozygote. Centimorgans are a unit of map distance. 1 centimorgan is equivalent to a 1% recombination frequency.
Gather Content
• What do you already know about linkage mapping by recombination?
o Linkage mapping uses recombination frequencies as a proxy for distance along the chromosome.
Consider Possibilities
• What other information is related to the question? Which information is most useful?
o Centimorgans are the unit of map distance. 1 centimorgan is equivalent to a 1% recombination frequency.
Choose Answer
• Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
o To analyze the data, we should first determine which were the likely parental chromosomes in the father. Since vg+ pr+ / vg pr (normal wings and red eyes) and vg pr / vg pr (vestigial wings and purple eyes) are the most common classes, those are the original paternal chromosomes.
o So the recombinant chromosomes are vg pr+ / vg pr (vestigial wings and red eyes) and vg+ pr / vg pr (normal wings and purple eyes).
o The recombinant chromosomes constitute the fraction of progeny: 80 + 70 / 420 + 80 + 70 + 430, or 150 / 1000.
o To determine the percentage recombination frequency, 150 / 1000 = 15 / 100 = 15%.
o Since 1% recombination = 1 cM, then 15% recombination is 15 cM.
Reflect on Process
• Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
o This question required you to Apply your knowledge and understanding to this unfamiliar situation.
o Did you remember that 1% recombination = 1 centimorgan?
o Did you recognize that you needed to determine which two classes were the recombinant classes?
o Did you determine the percent recombination using the equation : 80 + 70 / 420 + 80 + 70 + 430, or 150 / 1000?
You might also like to view...
A transport system in which transport of an ion in one direction provides the energy for active
transport in the opposite direction is known as ____.
a. antiport b. active diffusion c. symport d. cotransport e. osmosis
In what other areas of biological study is systematics important?
a. ecology b. physiology c. anatomy d. genetics e. all of the these
The two nucleotide sequences are
a. identical b. 80 to 90% the same c. 80 to 90% different d. none of the above
There are three aspects of entire populations that are important and often studied. Select the best choice from the ones listed.
A. a population's range, the pattern of spacing of individuals within the range, and the size that the population attains B. a population's range, the amount of food available within the range, and the size that the population attains C. a population's range, the parental care received by each offspring within the population, and the size that the population attains D. a population's range, the size home range of an individual in the population, and the parental care expended for each offspring