In these flies, the brown-eye allele (b) is recessive to the normal red-eye allele (B). However, a fly that has a normal body color may have the homozygous genotype EE or the heterozygous genotype Ee.

Because the genotypes Aa and AA both result in the grey fur phenotype, the probability that the offspring will have grey fur is (or 75%), and the probability that the offspring will have white fur is.

If the two versions are different, you have a heterozygous genotype for that gene. For example, being heterozygous for hair color could mean you have one allele for red hair and one allele for brown hair. The relationship between the two alleles affects which traits are expressed.

An organism with one dominant allele and one recessive allele is said to have a heterozygous genotype. In our example, this genotype is written Bb. Finally, the genotype of an organism with two recessive alleles is called homozygous recessive. In the eye color example, this genotype is written bb.

Symptoms of a MTHFR mutation

• cardiovascular and thromboembolic diseases (specifically blood clots, stroke, embolism, and heart attacks)
• depression.
• anxiety.
• bipolar disorder.
• schizophrenia.
• colon cancer.
• acute leukemia.
• chronic pain and fatigue.

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If Alan also has one of each type of gene, their children can have one of four allele combinations: DD, Dd, dD and dd. In this case, their child is 75 percent likely to have dimples.

Predicting Offspring Phenotypes Therefore, in this cross, you would expect three out of four (75 percent) of the offspring to have purple flowers and one out of four (25 percent) to have white flowers.