Relate the structure of a particular protein such as hemoglobin to the function it performs, noting how errors in amino acid sequencing alters the function. The similarity of human DNA sequences and the resulting similarity in cell chemistry and anatomy identify human beings as a single species. Discuss the difficulty of defining a species and explain the biological meaning of species, e.g., the constant reclassification of some bird species. The sorting and recombination of genes in sexual reproduction results in a countless possible gene combinations from the offspring of any two parents. Discuss why the number of chromosomes in gametes is one half the chromosome number in body cells.
Genes are segments of DNA molecules.
Inserting, deleting, or substituting DNA segments can alter genes. An altered gene may be passed on to every cell that develops from it. The resulting features may help, harm, or have little or no effect on the offspring's success in its environment. Gene mutations can be caused by such things as radiation and chemicals. The experiences an organism has during its lifetime can affect its offspring only if the genes in its own sex cells are changed by the experience.