Heredity
Heredity is the manner in which genetic traits are passed on to the next generation.
Chromosomes are the means through which the genetic material is transferred. The process of meiosis makes a sex cell or gametes, which holds just one set of a parent's chromosomes twenty-two plus a sex chromosome. During sexual reproduction, both sets of chromosomes are joined when the egg is fertilized by the sperm. Fertilization combines the genetic material from both parents, fusing to form a zygote, the first cell of a new individual. 23 As a result, the offspring has the combined genetic material of both parents. Consequently, each cell will have a pair of each chromosome, which results in a pair of genes for each trait. The positions of the two genes on the chromosome are alleles, or one's genotype. One allele is often dominant over the other. The dominant allele is expressed and can often be observed as physical trait, like eye color, right or left handedness, freckles, and curly hair. The observable trait is called one's phenotype, on the other hand, an unexpressed trait is called a recessive gene. We inherit many different traits including physical, behavioral, and predispositions to medical conditions like sickle-cell anemia, cystic fibrosis, heart disease, cancer, and some mental illnesses. 24
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