Genes (alleles) determine sequence of amino acids, which in turn influence the structure of proteins, which influence all structures and biochemical aspects of the organism.

DNA Each gene is composed of deoxyribonucleic acid (adenine, guanine, cytosine, thymine)

Bases There are 3-4 billion base pairs (AGCT) making the strand of DNA. The specific arrangement of these bases determines the amino acids and proteins to be created by the gene.

Chromosomes All genes found withing the 46 chromosomes in each somatic cell.

Genotype Total genes found in an individual’s cell.

Phenotype Total genes which are activated and can be observed.

Dominant genes Genes which will always be a part of phenotype.

Recessive genes Genes which will only be a part of phenotype if there are no dominant genes.

Why sex? Transmit genes into next generation. Promotes variation.

How sex? Through meiosis 23 pairs of chromosomes split (crossing over) to become 23 chromosome sex cells (sperm and ova).

What sex? Sex linked chromosomes (xx,xy) and testes activating factor.

Descent with modification is the result.

What? Variation among descendants.

How? Meiosis, recombination of genes, mutations.

Result? Variation, variation, variation.

*** Most offspring do not survive to reproduce. Variation increases the likelihood that someone will have a trait which aids their survival in competition with others, environment, predators, parasites.

*** "Nature" selects the winners (fitness). In addition to natural selection, note sexual and artificial selection. For example, most things we eat are genetically modified through artificial selection.

Over time, traits (and their genes) change in a population because of selection of variants. May lead to speciation.