Two brown-eyed parents have produced three blue-eyed sons. what can be concluded about the parents? a)only the father carries an allele for blue eyes. b)only the mother carries a dominant allele for blue eyes. c)the allele for blue eyes is on the father's y chromosome. d)they both carry a recessive allele for blue eyes.

Option D,they both carry a recessive allele for blue eyes.

Explanation:

A recessive allele is expressed only when the recessive allele are in pairs.

In this case, if "B" represents brown color of eye and "b" represents blue color of eye, then the genotype of blue eyed sons would be "bb"

Thus, both the parents must be a carrier of recessive allele so that each of them can contribute one blue color allele to their son.

Hence option D is correct.

photosynthesis makes the glucose that is used in cellular respiration to make atp. the glucose is then turned back into carbon dioxide, which is used in photosynthesis. while water is broken down to form oxygen during photosynthesis, in cellular respiration oxygen is combined with hydrogen to form water.