Biological Information

Key concepts:
• this definition states the relationship that exists between the physical and informational parts of a living organism.
• the physical nature of an organism is its phenotype
• the informational component is its genotype

Phenotype

Key concepts:
• the phenotype of an organism consists of all those parts that can be seen, touched, measured, or analyzed.
• the phenotype is the sum of the atoms, molecules, macromolecules, cells, tissues, and organs.
• the phenotype also consists of such processes and functions as energy metabolism, enzyme action, reflexes, behavioral patterns and even life span.

Genotype

Key concepts:
• biological information is stored information, a set of "blue prints" or instructions used to build and maintain a living organism.
• these instructions are carried inside (internal) the cells.
• the instructions are written in a genetic "code" that scientists can now read and understand.
• at cell division or sexual reproduction these coded instructions are copied, and a copy is passed onto the next generation.

Relationship

Key concepts:
• genotype codes for phenotype.
• organisms store enough genetic information in their cells to direct the production of all the physical parts of an organism.
• cells follow their stored instructions when constructing their macromolecules and other structures.

A trait

Key concepts:
• an organism such as a plant has an enormous phenotype that includes everything from its shape, its leaves, its flowers, its cells, its enzymes, etc.
• one small part of the phenotype of such a plant is the color of its flowers. Assume that this plant has red flowers.
• red flower color is considered to be a trait.
• this trait is determined by stored information within the cells of the plant.

Why is the flower red?

Key concepts:
• the petals of a flower are modified leaves built up from plant cells.
• the cells of the petal can be observed under a light microscope and seen to contain granules of red pigment.
• white light strikes these pigment granules. Most wavelengths of the light are absorbed and only the red light is reflected.
• plant flowers are red because of the red pigment their cells contain.

Where does the pigment come from?

Key concepts:
• a chemical reaction takes place in the cytoplasm of a cell in which a colorless molecule is changed to a different molecule that now absorbs light and reflects red light.
• without assistance, this reaction would take place very slowly and not much pigment would be produced during the life of the plant.
• thus, as with almost all chemical reactions inside cells, this reaction is catalyzed by an enzyme which speeds up the rate of the reaction hundreds of thousands of times.
• in the presence of the enzyme enough pigment is produced to quickly turn the cells and petals of the flower red.
• without the enzyme the cells would essentially stay colorless, with the enzyme the plant flowers can turn red.
• the red flower trait is thus the result of the activity of an enzyme.

The key role of proteins

Key concepts:
• as in this example, the enzyme that catalyzes the production of pigment, is a protein.
• other proteins transport material through membranes, keep the cell in its correct shape and move internal structures around to where they are needed.
• a large number of traits are produced and controlled by a wide variety of different proteins.
• proteins are facilitators, macromolecular "workers" that perform a whole range of "jobs" needed by cells and organisms.
• with the protein present the "job" gets done. When the protein is absent the "job" does not get done and the trait it produces is no longer present.

Proteins are macromolecular polymers

Key concepts:
• there are about 22 common amino acids found in proteins.
• amino acids are linked to one another by peptide bonds to produce a polypeptide chain.
• the sequence, or order, of the amino acids along the polypeptide chain is a critical property of the molecule.
• the sequence, or order, of amino acids determines the final shape of the protein and hence its function (in this case an enzyme with an active site).

Genotype codes for protein

Key concepts:
• stored in the genotype is the information that enables cells to get their amino acids in the right order.
• the information lists, using the genetic code, the correct sequence of amino acids.
• cells follow the sequence of coded instructions and join together amino acids in the order specified.
• once the polypeptide is formed it folds into an active protein (in this case an enzyme) which goes to work and produces a trait within the cell.
• the sum of those protein produced traits becomes the total phenotype of the organism.
• in this case, the genotype specifies the amino acid sequence that will produce and enzyme that will turn the flower red.