Question

which of the following statements correctly describes a dihybrid cross?
a dihybrid cross involves two parents.
a dihybrid cross produces two offspring.
a dihybrid cross involves organisms that are heterozygous for two characters.
a dihybrid cross results in a 3:1 phenotype ratio in the f2

question 2
what was the most significant conclusion that gregor mendel drew from his experiments with pea plants?
there is considerable genetic variation in garden peas.
traits are inherited in discrete units and are not the results of the \blending\ of traits.
recessive genes occur more frequently in the f1 generation than do dominant ones.
an organism that is homozygous for many recessive traits is at a disadvantage.

Explanation:

• For the first question:
• A dihybrid cross is specifically defined as a cross between two organisms that are heterozygous for two different traits (characters). Just involving two parents (which is true for many crosses) or producing two offspring (which is not a defining characteristic) or having a \(3:1\) ratio (which is for monohybrid cross F2) is incorrect.
• For the second question:
• Mendel's key conclusion was that traits are inherited as discrete units (genes). The idea of genetic variation in garden peas was known before in a general sense. Recessive genes do not occur more frequently in F1 (dominant traits are expressed in F1 when crossing pure - breeding parents). And the statement about an organism homozygous for many recessive traits being at a disadvantage was not Mendel's most significant conclusion.

Answer:

• First question: A dihybrid cross involves organisms that are heterozygous for two characters.
• Second question: Traits are inherited in discrete units and are not the results of the "blending" of traits.