Genes
Genes are molecules of nucleotides that encode for the traits seen in organisms, including humans. Genes are the code used to create proteins. These proteins are used for human traits. Blue eyes, skin color, height and facial features are all specific to the way these genes are arranged during conception. A person inherits one set of genes from the father and the other set of genes from the mother. Genes are contained in sets of chromosomes. The number of chromosomes in an organism differs. Humans contain 23 pairs of chromosomes. One pair is the sex pair, which determines the gender of the person.
Meiosis
Meiosis is the process that defines genetic variance. Genetic variance is what creates the unique features of the person. Meiosis only occurs in the sex cells in the human. These sex cells are sperm in men and the egg in females. When meiosis occurs, the chromosomes line up along the middle of the cell. During this time, genetic "crossing over" occurs. This means genes transfer across chromosomes. This provides a much higher rate of genetic variance that is inherited by offspring. Additionally, sex genes only have half the number of chromosomes. Therefore, 23 chromosomes are in sperm and eggs. When conception occurs, half the genes come from the sperm and the other half come from the egg. Therefore, offspring inherit half the genes from each parent.
Genotype
Alleles are the same gene located on each part of the chromosome. There are two types of alleles: dominant and recessive. A dominant trait persists and "silences" the recessive allele. For instance, brown eyes are a dominant trait, while blue eyes are recessive. Therefore, a person who inherits the brown eye allele and the blue eye allele will display brown eyes. Some traits blend, such as eye color, so the traits can be a mixture of blue and brown to form hazel eyes. The same blending of inherited traits occur for skin and hair color. Dominant and recessive traits also determine if a person inherits certain genetic diseases such as color blindness and hemophilia.
