In Drosophila, singed bristles (sn)and carnation eyes (car)are both caused by recessive X-linked alleles.The wild-type alleles (sn + and car + )are responsible for straight bristles and red eyes, respectively.A sn car female is mated to a sn + car + male and the F 1 progeny are interbred.The F 2 are distributed as follows:
$$\begin{array} { | l | r | }
\hline s n~ c a r & 55 \
\hline s n~ c a r^+ & 45\
\hline s n ^{+ c a r} & 45 \
\hline s n ^ { + c a r +} & \underline{55} \
\hline & 200 \
\hline
\end{array}$$
-If you want to analyze this data for evidence of linkage between sn and car, what is the null hypothesis?
A)Genes sn and car are linked.
B)Genes sn and car are not linked.
C)Genes sn and car are located close together on the same chromosome.
D)Crossing-over sometimes occurs between sn and car.

Question

In Drosophila, singed bristles (sn)and carnation eyes (car)are both caused by recessive X-linked alleles.The wild-type alleles (sn + and car + )are responsible for straight bristles and red eyes, respectively.A sn car female is mated to a sn + car + male and the F 1 progeny are interbred.The F 2 are distributed as follows:
 $$\begin{array} { | l | r | } 
\hline s n~ c a r & 55 \
\hline s n~ c a r^+ & 45\
\hline s n ^{+ c a r} & 45 \
\hline s n ^ { + c a r +}  & \underline{55} \
\hline & 200 \
\hline
\end{array}$$ 
-If you want to analyze this data for evidence of linkage between sn and car, what is the null hypothesis?
A)Genes sn and car are linked. 
B)Genes sn and car are not linked. 
C)Genes sn and car are located close together on the same chromosome. 
D)Crossing-over sometimes occurs between sn and car.

Quizplus · Accepted Answer

The null hypothesis typically assumes no effect or no relationship between variables. In this context, stating that genes sn and car are not linked assumes no relationship between their locations, which is what you would test against to find evidence of linkage.

In Drosophila, Singed Bristles (Sn)and Carnation Eyes (Car)are Both Caused