Why Are the Progeny of a Testcross Generally Used to Map

question 4

Multiple Choice

Why are the progeny of a testcross generally used to map loci? Why not the F₂ progeny from an F₁ × F₁ cross?

• A) Only recombinant offspring would be found in the progeny of an F₁ × F₁ cross.
• B) The progeny of an F₁ × F₁ cross would be found in a 9:3:3:1 ratio when two genes are involved, whereas the progeny of a testcross would result in a 1:1:1:1 ratio.
• C) It is easier to classify recombinant and parental offspring of a testcross than with the progeny of an F₁ × F₁ cross.
• D) In a testcross more of the progeny would be expected to display the dominant phenotype than in the progeny of an F₁ × F₁ cross.
• E) A testcross is more useful for mapping genes that are located near each other but, when genes are quite far apart on the same chromosome, an F₁ × F₁ cross actually is more useful.

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Definitions:

Independent Variables

Variables that are manipulated or controlled in an experiment to test their effect on dependent variables.

Random Assignment

A method used in experiments to divide participants into groups in a way that each has an equal chance of being placed in any group, minimizing biases.

Generalizable

The extent to which findings from a study can be applied or extended to larger populations beyond the sample studied.

Client Variables

Aspects or characteristics of clients that might influence the outcome of a service, program, or study, such as their background or personal preferences.