Anonymous
Anonymous asked in Science & MathematicsBiology · 1 month ago

A certain species of plant usually has leaves with seven leaflets.?

 A certain species of plant usually has leaves with seven leaflets. Your not-so-good friend Jim is a bit of a horticulturalist and grows these plants at home. He notices a plant with five-leaflet leaves and decides to breed a five-leaflet variety. However, every time he crosses five-leaflet plants to each other, he gets a 2:1 ratio of five-leaflet and seven-leaflet progeny. And every time he crosses a five-leaflet plant to a seven-leaflet plant, he gets 1:1 ratio of five-leaflet and seven-leaflet progeny. With a genuinely puzzled look on his face, he comes to you, the biology major, for advice. These observations are best described by:

a. the five-leaflet and seven-leaflet alleles are co-dominant for leaflet number

b. the five-leaflet allele is incompletely dominant over the seven-leaflet allele for leaflet number

c. the five-leaflet allele is homozygous recessive for lethality

d. the seven-leaflet allele is homozygous recessive for lethality

e. All of the above scenarios are equally likely and chill

1 Answer

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  • 1 month ago

    Badly worded, and none of the choices are good.

    A.  No.  You're not seeing any plants with both 5 and 7 leaflets on the same plant, so you can't say it's codominance.

    Eliminating A also eliminates E.

    So now here's a scenario:  F and f are alleles for the same gene locus.  F stands for "Five" and f stands for "Seven."

    FF is lethal.

    Ff is a heterozygote which has five leaflets.

    ff is a homozygous recessive.

    You can do your Punnett squares with that and find that you get the observed ratios.

    This situation does not quite fit with any of the remaining choices.

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