Gregor mendel formulated his laws of heredity in 1860 before

In explanation.

Explanation:

Gregor Mendel formulated his laws of heredity in 1860 before...

-The structure of DNA was known, the existence of chromosomes and genes were known and the mechanisms which create variation in offspring were known.

If your quiz is like this:

Question: Gregor Mendel formulated his laws of heredity in 1860 before .

A). The structure of DNA was known.

B). The existence of chromosomes and genes was known.

C). The mechanisms which create variation in offspring were known.

D). All of the choices above are correct.

E). An understanding of mitosis and meiosis was known.

The correct answer is the "D" because yes after Gregor Mendel formulated his laws of heredity in 1860 the structure of DNA was known, the existence of chromosomes and genes were known and the mechanisms which create variation in offspring were known. (Referring that A, B, and C are correct).

Hope this helps.

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