Females Heterozygous for the Recessive Second Chromosome Mutations Px, Sp

question 60

Multiple Choice

Females heterozygous for the recessive second chromosome mutations px, sp, and cn are mated to a male homozygous for all three mutations.The offspring are as follows:
\begin{array}{|l|r|}\hline p x  s p  c n & 1461 \\\hline p x  s p  c n^{+} & 3497 \\\hline p x  s p{+ c n} & 1\\\hline p x  s p^{+}  c n+ & 11 \\\hline p x^{+}  s p  c n & 9 \\\hline p x^{+}  s p  c n+ & 0 \\\hline p x^{+}  s p+ c n & 3483 \\\hline p x^{+}  s p+ c n+ & 1539 \\\hline & 10,000 \\\hline\end{array}
-Which of the following linkage maps correctly shows the order and distance between the px, sp, and cn genes?

• A)sp--0.21 m.u.--px--30.01 m.u.--cn
• B)sp--30.01 m.u.--px--0.21 m.u.--cn
• C)sp--0.2 m.u.--px--30 m.u.--cn
• D)px--0.2 m.u.--sp--30.2 m.u.--cn
• E)px--30.2 m.u.--sp--0.2 m.u.--cn

---

Definitions:

Skin Surface

The outermost layer of the skin that protects the body from the external environment, including pathogens and physical damage.

Hair Bulb

The rounded, bulbous base of a hair follicle containing actively dividing cells which produce the hair shaft.

Cuticle

The cuticle is a protective and waxy or hard outer layer found on the surface of plants, hairs, nails, and other surfaces, serving as a barrier against environmental damage.

Medulla

A section of the brainstem that controls vital bodily functions such as heartbeat and breathing.