From Genes To Proteins

Chapter 10, Section 1: From Genes to Proteins

Proteins have many functions, including acting as enzymes and cell membrane channels. Proteins, however, are not built directly from DNA. Ribonucleic acid is also involved.

Like DNA, ribonucleic acid (RNA) is a nucleic acid--- a molecule made up of nucleotides linked together.

RNA differs from DNA in 3 ways

o RNA consists of a single strand of nucleotides, instead of 2 strands found in DNA.

o RNA nucleotides contain the 5 carbon sugar ribose rather than the sugar deoxyribose found in DNA nucleotides.

o In addition to A, G, and C nitrogen bases found in DNA, RNA nucleotides have a nitrogen base called uracil. No thymine bases are found in RNA.

A gene's instructions for making a protein are coded in the sequence of nucleotides in the gene. The instructions for making a protein are transferred from a gene to an RNA molecule in a process called transcription. Cell then use 2 different types of RNA to read the instructions on the RNA molecule and put together the amino acids that make up the protein in a process called transcription. The entire process by which proteins are made based on the information encoded in DNA is called gene expression, or protein synthesis.

The first step in the making of a protein, transcription, takes the information found in a gene in the DNA and transfers it to a molecule of RNA. RNA polymerase, an enzyme that adds and links complementary RNA nucleotides during transcription, is required.

Steps of transcription

Transcription begins when RNA polymerase binds to the genes promoter--a specific sequence of DNA that acts as a "start" signal for transcription

RNA