Prentice Hall- Science Explorer- Cells and Heredity
Chapter 3- The Science of Heredity
Section 4- The DNA Connection
Questions- Comments- Key Words- Connections |
Main Ideas; Visuals + PredictionsThe Genetic Code
*The main function of genes is to control the production of proteins in an organism’s cells. Proteins help to determine the size, shape, color, and many other traits of an organism. |
Messenger RNA Transfer RNA |
Genes and DNA
*DNA molecule is made up of four different nitrogen bases—adenine (A), thymine (T), guanine (G), and cytosine (C). These bases form the rungs of the DNA “ladder" or Double helix. Order of the Bases *The order of the nitrogen bases along a gene forms a genetic code that specifies what type of protein will be produced. How Cells make Proteins *During protein synthesis, the cell uses information from a gene on a chromosome to produce a specific protein. *Protein synthesis takes place on the ribosomes in the cytoplasm of a cell. The role of RNA *RNA is has only one strand *Like DNA, RNA contains adenine, guanine, and cytosine. However, instead of thymine, RNA contains uracil. Types of RNA Messenger RNA: RNA that copies the coded message from DNA in the nucleus and carries the message into the cytoplasm. Transfer RNA: RNA in the cytoplasm that carries an amino acid to the ribosome and adds it to the growing protein chain. |
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Mutations
*Mutations can cause a cell to produce an incorrect protein during protein synthesis. As a result, the organism’s trait, or phenotype, may be different from what it normally would have been. *Mutations can be helpful, neutral or harmful depending on how it affects the organisms ability to survive in its environment. |