## DNA, RNA, Chromosomes, and Genes## Genetics and the Human Genome |

## What is the relationship between probability and genetics? |

Yes, the environment can affect genes. For example, some genes are sensitive to temperature—like the enzyme that controls the synthesis of black pigment melanin in Siamese cats, which is only active at cool temperatures. The cooler the body part, the darker the pigment; since the body is warmer than the extremities, it remains lighter in color. During the winter if your Siamese cat goes outdoors, the fur may become darker, while Siamese kittens are usually white due to the warmth of the mother’s body.

Probability is a branch of mathematics used to predict the likelihood of an event occurring. It is also an important tool for understanding inheritance patterns of specific traits. Two rules are applied to genetic inheritance: 1) The rule of multiplication is used when determining the probability of any two events happening simultaneously. For example, if the probability of having dimples is ¼, and the probability of having a male child is ½, then the probability of having a boy with dimples is ¼ × ½, or1⅛) The rule of addition is used when determining the outcome of an event that can occur in two or more ways. For example, if we were to consider the probability of having a male child or of having a child with dimples, then the probability would be ½ ¼, or ¾. In other words, chances are 3 out of 4 that a given birth will produce a male child or a child with dimples.