GENETICS

Nucleus Our cells are controlled by the nucleus. The nucleus also contains our genetic information on structures called chromosomes.

Chromosomes Humans have 46 chromosomes in each body cells, or 23 pairs. The chromosomes themselves are made of thousands of genes (over 60,000 in humans). Each parent contributes half of each chromosome pair to their offspring.

Genes The genes themselves actually control for different traits. For example a gene may control for eye color. All genes come in pairs. Half of the pair coming from mother, the other half coming from father.

Alleles There are different forms of genes called alleles. For example, brown eyes or blue eyes.

Dominant and Recessive Some genes are dominant or stronger and will appear more often. Others are recessive or weaker and will appear less often. For example brown eyes are dominant over blue, and appear more often.

Genes Dominant genes are always represented by a capital letter. Recessive genes are always represented by a lowercase letter. m j a

Because half of the genetic information is given from each parent there are different possibilities for which traits show in the offspring. Let’s use eye color as an example. B represents the dominant trait, brown and b represents the recessive trait of blue. the child could have B from one parent and B from the other = child with brown eyes the child could have b from one parent and b from the other = child with blue eyes ***Any time the dominant gene appears, the offspring will have the dominant trait.

The Chromosome Theory of Inheritance states that: genes are carried from parents to their offspring on chromosomes.