Question

in a particular species of octopus, long arm length is completely dominant over short
if an octopus of this species has long arms, what is its genotype?
○ dd
○ dd only
○ dd or dd
○ d

Explanation:

Step1: Understand dominant and recessive traits

In genetics, a dominant trait (long - arm length here) is expressed when at least one dominant allele is present. A recessive trait (short - arm length) is expressed only when two recessive alleles (\(dd\)) are present.

Step2: Analyze genotypes

• If the genotype is \(DD\), since \(D\) (long - arm allele) is dominant, the octopus will have long arms.
• If the genotype is \(Dd\), the presence of the dominant \(D\) allele means the octopus will also have long arms.
• The genotype \(dd\) would result in short arms (recessive trait). And \(D\) is not a valid genotype representation (genotypes are pairs of alleles). So an octopus with long arms can have genotype \(DD\) or \(Dd\).

Answer:

C. \(DD\) or \(Dd\)