How can you tell the genotype if an organismexpresses or presents a recessive phenotype.  What are some examples of this?

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2 Answers

If an organism expresses a recessive phenotype it must be carrying two recessive alleles.  The recessive trait is only expressed if there is no dominant allele.  As an example, let’s say that flower color is determined by one gene.

There are red and blue flowers.

Red is dominant

Blue is recessive

You have the following for genotypes

FF, Ff, fF, ff

Any genotype with a big F has the dominant red allele.  The phenotype will be a red flower.  If there is no big F then the blue allele will be expressed.




Red Flowers


Red Flowers


Red Flowers


Blue Flowers

The ff genotype will display the recessive gene because there is no big F to be dominant.

by Level 3 User (8.5k points)

If an organism is displaying the recessive phenotype, then you always know thegenotype (assuming there's only one gene involved). Take the example of blood type(which I know is multi-gene, but it's a good example). If someone has blood-type A, they could have the genotype AA, Aa, or Ai. However, for blood-type O, which is the recessive phenotype, the only genotype possible is ii.

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