Chapter 3, Section 4 The DNA Connection Monday, November 16, 2009 Pages

Objectives Explain the term “genetic code”. Describe the process by which a cell produces proteins. Describe the different types of mutations and how they affect organism.

Vocabulary Words Messenger RNA Transfer RNA Mutation

Review… The main function of genes is to control the production of proteins in the organism’s cells. Proteins help to determine the size, shape, and many other traits of an organism. DNA is the major component of chromosomes.

Review--cont’d… A DNA molecule is made up of four different nitrogen bases (A, T, G, C). Nitrogen bases for the rungs of the DNA ladder. A single gene on a chromosome may contain anywhere from several hundred to a million or more bases.

Genetic Code The order of the nitrogen bases along a gene forms a genetic code that specifies what type of protein will be produced. In the genetic code, a group of 3 bases code for the attachment of a specific amino acid. The order of these bases determine the type of protein.

Protein Synthesis Protein synthesis the process in which protein is produced. During protein synthesis, the cell uses information from a gene on a chromosome to produce a specific protein. Protein synthesis occur on the ribosomes in the cytoplasm of the cell.

The Role of RNA RNA is the genetic messenger that carries the genetic code from the DNA inside the nucleus to the cytoplasm. Physically, RNA looks like half a ladder.

RNA vs. DNA Looks like half a ladder. Contains a different sugar molecule. Nitrogen base is different. RNA contains uracil instead of thymine.

RNA There are 2 types of RNA involved in protein synthesis. Messenger RNA Copies the code message from the DNA in the nucleus and carries the message into the cytoplasm. Transfer RNA Carries amino acids and adds them to the growing protein chain.

Protein Synthesis DNA Nucleus Messenger RNA Ribosome Protein Amino Acid Transfer RNA Protein

Mutations A mutation is any change that occurs in a gene or chromosome. Mutations can cause a cell to produce an incorrect protein during protein synthesis. Result: The phenotype will be different than expected.

Types of Mutations Mutations occurring protein synthesis. Substitution of a nitrogen base DNA replication process Incomplete separation during meiosis. Mutations in a body cell.

Effects of Mutations A source of genetic variety. Some changes are harmful to the organism. It reduces the organism’s chances for survival and reproduction. Example: Cancer. Some changes are helpful. Improves an organism’s chances for survival and reproduction. Some changes are neither harmful nor helpful.

Homework Workbook 3.4 (due 11/18) Vocabulary quiz 3.4 (11/18)