Gregor Mendel’s pioneering genetic experiments with pea plants occurred before the discovery of the structure and function of chromosomes. Which of the following observations about inheritance in pea plants could be explained only after the discovery that genes may be linked on a chromosome?

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BlackTom AI · Accepted Answer

First, let's restate what we have. The question asks about Mendel's pea plant experiments and asks which observation could be explained only after the idea that genes may be linked on a chromosome, given that his work predated our understanding of chromosomes.

Option under consideration: "Most offspring in a given cross had a combination of traits that is identical to that of either one parent or the other."

Now, to analyze this option in context:
- If genes are not linked and assort independently, dihybrid crosses typically produce a mix of parental and recombinant phenotypes, as Mendel observed with his 9:3:3:1 ratio in many cases. This implies that offspring frequently show combinations not identical to either parent.
- If genes are linked on the same chromosome, especially when crossing over is rare or limited, parental allele combinations tend to be inherited together. This would result in a higher proportion of offspring whose trait combinations match one of the parents, i.e., parental types, rather than new recombinant combinations.
- Therefore, the statement that most offspring are identical to one parent or the other could be explained by linkage, and would be a clue that genes are linked rather than independently assorted. This is the kind of pattern that would become explainable only after recognizing linkage on chromosomes, because independent assortment cannot readily account for a strong bias toward parental combinations.

However, there are caveats:
- In many real crosses, recombination occurs, and you still observe some non-parental (recombinant) phenotypes. The extent of parental types versus recombinants depends on how tightly linked the genes are and on recombination frequency.
- The presence of parental-type predominance alone is not universal proof of linkage; you would need further data (such as reduced recombination frequencies in dihybrid crosses) to conclude linkage definitively.

In the absence of other answer choices, this option highlights the concept that a pattern of offspring identical to a parent becomes more interpretable if genes are linked, because linkage preserves parental allele combinations across generations rather than mixing them completely as independent assortment would.

In sum, the statement aligns with the idea that linkage can explain a preponderance of parental-type offspring, something not readily explained by Mendel’s original model of independent assortment. If other options were present, we’d compare them to see which could only be explained by linkage versus which could be explained by other phenomena (e.g., mutations, pleiotropy, or epistasis).

APBIO141-031 with labs Unit 5 Test

Gregor Mendel’s pioneering genetic experiments with pea plants occurred before the discovery of the structure and function of chromosomes. Which of the following observations about inheritance in pea plants could be explained only after the discovery that genes may be linked on a chromosome?

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