An interactive Punnett Square inheritance calculator to work out patterns of recessive inheritance for a trait, such as straight or peaked hairline.

An example of a recessive genetic trait is straight hairline (versus peaked). What is the chance a child will have a straight hairline? Drag an icon from the top for the mother and father, representing the gene combinations that determine straight or peaked hairline. Tap MATE and see all possible gene combinations for offspring based on the parents’ genes. A recessive trait results when offspring inherit two copies of a recessive gene (t) – one from each parent. In this case, 1 of 4 possible gene combinations is tt, so 25% of offspring will have a straight hairline. Tt offspring (50%) have one dominant and one recessive gene; they will not have a straight hairline but are “carriers” of the recessive gene. Tap OFFSPRING to see which of the four possible gene combinations may occur for the first pregnancy. A TT offspring does not have a straight hairline. There is no possibility of passing on a recessive gene (t) to the next generation. A Tt offspring does not have a straight hairline, but is a “healthy carrier” with one copy of the recessive gene (t) that may be passed on to the next generation. A tt offspring has a straight hairline, and will pass the recessive gene (t) on to the next generation. Tap OFFSPRING again to see which of the four possible gene combinations may occur for another pregnancy.

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