Gene S Controls the Sharpness of Spines in a Type

question 60

Multiple Choice

Gene S controls the sharpness of spines in a type of cactus. Cactuses with the dominant allele, S, have sharp spines, whereas homozygous recessive ss cactuses have dull spines. At the same time, a second gene, N, determines whether or not cactuses have spines. Homozygous recessive nn cactuses have no spines at all. A cross between a true-breeding sharp-spined cactus and a spineless cactus would produce ________.

• A) all sharp-spined progeny
• B) 50 percent sharp-spined, 50 percent dull-spined progeny
• C) 25 percent sharp-spined, 50 percent dull-spined, 25 percent spineless progeny
• D) all spineless progeny
• E) It is impossible to determine the phenotypes of the progeny.

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Definitions:

Cast Iron Pipe

A type of durable pipe made from iron that has been cast in a mold, often used for water or sewage systems.

ABS Pipe

Acrylonitrile Butadiene Styrene pipe, a type of plastic piping used for waste water and vent lines due to its high resistance to impact and durability.

Valves

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Reducing Fittings

Pipe fittings used to connect pipes of different diameters, allowing for a change in pipe size.