Antigens on red blood cells are hereditary traits that allow blood to be typed in different ways. One system is based on a gene with two alleles, M and N. If the frequency of the M allele in a population is 0.4, then according to the Hardy-Weinberg rule, the expected frequency of the heterozygous MN genotype is ___.

Question

A.  0.16
B.  0.24
C.  0.36
D.  0.48
E.  0.6

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?
· What key words does the question contain and what do they mean?
 
Gather Content· What do you already know about the Hardy-Weinberg principle? How does it relate to the question?

  Consider Possibilities
· What other information is related to the question? Which information is most useful?
 
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?

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?
 

Answer 1

D.  0.48

Clarify Question
· What is the key concept addressed by the question?
        o This question is asking you to calculate various frequencies for a population in Hardy-Weinberg equilibrium. What are the formulas involved in calculating the frequencies for a population in Hardy-Weinberg equilibrium?
· What type of thinking is required?
        o This is an analyze question because you have to calculate various frequencies for a population in Hardy-Weinberg equilibrium.
· What key words does the question contain and what do they mean?
        o Frequency, which refers to the number of times a particular event occurs in a sample.
        o Heterozygote, which means the individual contains different alleles for the gene.
        o Hardy-Weinberg equilibrium, which refers to populations whose genotype frequencies do not change from generation to generation.
        o Allele, which refers to a version of a gene.
 
Gather Content· What do you already know about the Hardy-Weinberg principle? How does it relate to the question?
        o To solve this problem you will need to apply the Hardy-Weinberg equations. Recall that there are two equations involved in the Hardy-Weinberg principle. One equation is p + q = 1; where p is the frequency of the dominant allele, q is the frequency of the recessive allele, and 1 is 100% of the alleles. The other equation is p2 + 2pq + q2 = 1; where p2 is the frequency of the homozygous dominant genotype, 2pq is the frequency of the heterozygous genotype, q2 is the frequency of the homozygous recessive genotype, and 1 is 100% of the individuals. How are these two equations related? How can we go from a homozygous genotype frequency to an allele frequency?

  Consider Possibilities
· What other information is related to the question? Which information is most useful?
        o The question provides you with an allele frequency. How can you find the other allele frequency and subsequently the heterozygous genotype frequency?
 
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o The question provides you with two different numbers to calculate the frequency of a dominant phenotype. One of these numbers is the part of the population expressing the trait and the other number is total population. How can you calculate a frequency if you know the number expressing the trait of interest and the number for the whole population?
        o How do you get from a value that is squared, like p2, to a value that is not squared but has the same variable, like p? What is the mathematical function involved in this process?

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 asked you to determine the frequency of the heterozygous MN blood type.
        o Answering this question correctly depended not only on distinguishing between genotypic and phenotypic frequencies, but on your ability to break down, or analyze, various frequencies.
        o If you got the correct answer, excellent! If you got an incorrect answer, where did the process break down? Did you remember how to calculate the square root of a decimal? Do you understand that the recessive phenotype must have a homozygous recessive genotype? Therefore, the frequency of the recessive phenotype must equal the frequency of which genotype? Did you have trouble breaking down the Hardy-Weinberg equations to determine the correct answer?