Mendelian Genetics

AP Biology· difficulty 3/5

A red-flowered pea plant is crossed with a white-flowered pea (assumed homozygous recessive ww). The cross produces 53 red and 47 white offspring out of 100.

What does this 1:1 ratio reveal about the red-flowered parent?

  • A

    It is homozygous recessive (ww)

  • B

    Color is environmentally determined

  • C

    It is homozygous dominant (WW)

  • D

    It is heterozygous (Ww)

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Explanation

A test cross of the unknown red parent with white (ww) yields 1:1 if the red parent is Ww (Ww x ww gives 1/2 Ww red, 1/2 ww white). A WW parent would give 100% red.

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