A Geneticist Is Investigating the Inheritance of Two Autosomal Recessive

question 21

Short Answer

A geneticist is investigating the inheritance of two autosomal recessive genes in mice, one for obesity (LEP) and another for autism (oprm1). The table below provides the number of offspring observed, for each phenotype, when dihybrid mice are testcrossed: $$\begin{array} { | l | c | l | l | l | l | } \hline \text { Phenotype } & \text { Observed(O) } & \text { Expected } ( \mathrm { E } ) & \mathrm { O } - \mathrm { E } & ( \mathrm { O } - \mathrm { E } ) 2 & ( \mathrm { O } - \mathrm { E } ) 2 / \mathrm { E } \\\hline \text { wild- type } & 88 & & & & \\\hline \text { obese } & 68 & & & & \\\hline \text { autistic } & 64 & & & & \\\hline \text { obese, autistic } & 80 & & & & \\\hline & & & & & \sum ( \mathrm { O } - \mathrm { E } ) ^ { 2 } / \mathrm { E } = \\\hline\end{array}$$ Fill in the table above and determine:
a. the chi- square (χ²) value (to the nearest hundredth) for the chance hypothesis that the two genes assort independently
b. the degrees of freedom
c. whether or not you would reject your chance hypothesis that the two genes assort independently, based on approximate P value, and the justification for why

---

Definitions:

Aversive Event

An unpleasant or undesirable event that causes a negative reaction in an individual, often used in psychology to study behaviors and conditioning.

Organism

A living entity that can function independently, including animals, plants, fungi, microorganisms, and in some contexts, viruses.

Punishment Learning

A form of learning in which an undesirable behavior decreases in frequency because it is followed by an unpleasant stimulus.

Spanking

The act of striking the buttocks of another person to cause physical pain, typically used as a form of punishment.