In Humans,the Allele N Causes an Abnormal Shape of the Patella

question 21

Essay

In humans,the allele N causes an abnormal shape of the patella in the knee (n is the normal allele).A separate gene is concerned with finger length,and the allele B causes abnormally short fingers,whereas b gives normal length.A study focused on people who have both abnormal patellae and short fingers (they were most likely N/n ^. B/b in genotype),having inherited the N allele from one parent and the B allele from the other parent.These N/n ^. B/b people mated with normal spouses,producing 40 progeny classified as follows:
$$\begin{array} { l l } \text { Normal } & 3 \\\text { Abnomal knees and fingers } & 2 \\\text { Abromal knees only } & 17 \\\text { Abnomal fingers only } & 18\end{array}$$
a)Draw the chromosomes of the N/n ^. B/b individuals,their parents,and their four types of children,showing the positions of the alleles.
b)Explain why the four types of children were in the proportions shown.

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Definitions:

Biological Conditions

Physical states that affect the function and behavior of organisms, often relating to health and disease states.

Drive Reduction Theory

A motivational theory that argues the primary goal of all behavior is the reduction of drives, which are basic bodily needs.

Motivation

The method that starts, steers, and sustains behaviors aimed at achieving goals.

Reinforcement Value

The degree to which a specific outcome or reward increases the likelihood of a behavior occurring again.