Use the Following Information to Answer the Question If Recombination Frequency Is Equal to Distance in Map Units

question 26

Multiple Choice

Use the following information to answer the question.
A plantlike organism on the planet Pandora can have three recessive genetic traits: bluish leaves, due to an allele (a) of gene A; a feathered stem, due to an allele (b) of gene B; and hollow roots due to an allele (c) of gene C. The three genes are linked and recombine.
A geneticist performed a testcross with an organism that had been found to be heterozygous for the three recessive traits, and she was able to identify progeny of the following phenotypic distribution (+ = wild type) :
$$\begin{array} { | l | l | l | l | l | } \hline \text { Phenotypes } & \text { Leaves } & \text { Stems } & { \text { Roots } } & { \text { Number } } \\\hline1 & a & + & + & 14 \\\hline 2 & a & + & c & 0 \\\hline 3 & a & b & + & 32 \\\hline 4 & a & b & c & 440 \\\hline 5 & + & b & + & 0 \\\hline 6 & + & b & c & 16 \\\hline 7 & + & + & c & 28 \\\hline 8 & + & + & + & 470 \\\hline &&& \text { Total } & 1000 \\\hline\end{array}$$
If recombination frequency is equal to distance in map units, what is the approximate distance between genes A and B?

• A) 3 map units
• B) 6 map units
• C) 15 map units
• D) 30 map units

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