1. How are proteins made?
How are proteins made?

4. A structure found within the cytoplasm of cells, made up of protein and RNA, that serves as the site of protein synthesis.

5. Where is DNA stored?
Where are proteins built?

6. Even bacteria need to build proteins
To make an enzyme that it needs, the chemical mechanisms inside an E. coli cell make a copy of a gene from the DNA strand and use this template to form the enzyme. The E. coli might have thousands of copies of some enzymes floating around inside it, and only a few copies of others. The collection of 1,000 or so different types of enzymes floating in the cell makes all of the cell's chemistry possible. This chemistry makes the cell "alive" -- it allows the E. coli to sense food, move around, eat and reproduce.

9. Building A Protein click on title above to view important animation

10. How Life Works: DNA and Enzymes
To understand a gene pool, you need to know a little bit about genes. If you have read How Cells Work, then you are familiar with the inner workings of the E. coli bacteria and can skip this section. Here's a quick summary to highlight the most important points in How Cells Work
·A bacterium is a small, single-celled organism. In the case of E. coli, the bacteria are about one-hundredth the size of a typical human cell. You can think of the bacteria as a cell wall (think of the cell wall as a tiny plastic bag) filled with various proteins, enzymes and other molecules, plus a long strand of DNA, all floating in water.
·The DNA strand in E. coli contains about 4 million base pairs, and these base pairs are organized into about 1,000 genes. A gene is simply a template for a protein, and often these proteins are enzymes.

11. Sexual Reproduction
Bacteria reproduce asexually. This means that, when a bacteria cell splits, both halves of the split are identical -- they contain exactly the same DNA. The offspring is a clone of the parent.
As explained in How Human Reproduction Works , higher organisms like plants, insects and animals reproduce sexually, and this process makes the actions of evolution more interesting. Sexual reproduction can create a tremendous amount of variation within a species. For example, if two parents have multiple children, all of the children can be remarkably different. Two brothers can have different hair color, different heights, different blood types and so on. Here's why that happens:
·Instead of a long loop of DNA like a bacterium, cells of plants and animals have chromosomes that hold the DNA strands. Humans have 23 pairs of chromosomes, for a total of 46 chromosomes. Fruit flies have five pairs. Dogs have 39 pairs, and some plants have as many as 100.

12. Chromosomes come in pairs
Chromosomes come in pairs. Each chromosome is a tightly packed strand of DNA. There are two strands of DNA joined together at the centromere to form an X-shaped structure. One strand comes from the mother and one from the father. Because there are two strands of DNA, it means that animals have two copies of every gene, rather than one copy as in an E. coli cell.

13. When a female creates an egg or a male creates a sperm, the two strands of DNA must combine into a single strand. The sperm and egg from the mother and father each contribute one copy of each chromosome. They meet to give the new child two copies of each gene. To form the single strand in the sperm or egg, one or the other copy of each gene is randomly chosen. One or the other gene from the pair of genes in each chromosome gets passed on to the child.

14. Because of the random nature of gene selection, each child gets a different mix of genes from the DNA of the mother and father. This is why children from the same parents can have so many differences.
A gene is nothing but a template for creating an enzyme. This means that, in any plant or animal, there are actually two templates for every enzyme. In some cases, the two templates are the same (homozygous), but in many cases the two templates are different (heterozygous).