Know that cells in all species have as least two sets (diploid) of chromosomes each with a set of genes on them.  The two copies (pairs) or versions (alleles) of a gene, may or may not be identical.  These pairs of genes are called the genotype.  These alleles may be dominant or mostly ignored, overpowered, and not used (recessive).

Know that DNA (Deoxyribonucleic Acid) is the genetic material (chemical) of organisms and is either located in the nucleus as chromatin or packed in chromosome form.

Know that a segment of DNA that codes for a specific protein is called a gene. All the genes found on all the chromosomes are called the genome. Genes, to a large degree, determine the physical (and mental if it has a brain) traits called the phenotype.

Know that Meiosis: is a special type of cell division where reproductive cells (gametes) are produced, each with only one set of chromosomes (and the genes on them). It is part of the sexual reproduction process where each of offspring inherits half of their genes from each parent.  Sexual reproduction, mutation, experimentation, and environmental factors lead to genetic variation in a population

Know that Punnett Square charts are used to understand how genes are combined during fertilization and predict the heredity of how traits are passed on.