Predicting Traits

Probability means how likely it is that something will happen. The probability that something will happen can be calculated using mathematics.
In genetics, a kind of table is used to help predict inherited traits. This table is a Punnett square. A Punnett square is a table for predicting the outcome of crossing different forms of a trait. In a Punnett square, letters are used to represent factors for each trait. A capital letter stands for the dominant factor, and a lowercase letter stands for the recessive factor. To make a Punnett square, draw a large square and divide it into smaller squares. Write the parent's factor for each trait outside the square. Fill in each square with the letter above it and the letter to the left of it. The squares show all the possible combinations of traits in the offspring.
The combination of factors inherited by offspring is not exactly the same thing as physical appearance of the offspring. You can use the probability ratios obtained from a Punnett square to predict how many offspring will show a dominant trait and how many will show a recessive trait.
Humans inherit thousands of factors for traits from their parents. Humans inherit one factor for each trait from each parent. This results in a total of two factors for each trait in the child.
A pedigree is a chart used to trace the history of traits in a family. A pedigree shows which members of the family have a particular trait, such as curly hair, long eyelashes, or attached earlobes.
In a pedigree some individuals are called carriers. A carrier is an individual who has inherited a factor for a trait but does not show the trait. Some inherited traits do not follow the patterns of Mendel's basic ideas. There are some dominant factors that do not completely mask factors for the other form of the trait. In four-o'clock flowers, the dominant factor for color results in a red flower only if the plant has inherited two dominant factors for red color. Plants with one dominant factor for red color and one dominant factor for white color may have pink flowers. This pattern is called incomplete dominance.This is how you can predict traits.