What do genes specify

The role of DNA is similar to the role of the alphabet. It has the potential to carry information, but only if the letters are combined in ways that make meaningful words. Stringing words together makes instructions, as in a recipe. So genes are instructions for the cell. If genes are like a basic recipe, alleles Ah-LEE-uhls are versions of that recipe. We inherit one allele, or gene version, from each of our parents.

That means most of our cells contain two alleles, one per chromosome. The reason: Before we inherit them, alleles are shuffled like a deck of cards.

This happens when the body makes egg and sperm cells. They are the only cells with just one version of each gene instead of two , packaged into 23 chromosomes. Egg and sperm cells will fuse in a process known as fertilization. This starts the development of a new person. By combining two sets of 23 chromosomes — one set from the egg, one set from the sperm cell — that new person ends up with the usual two alleles and 46 chromosomes.

And her unique combination of alleles will never arise in the exact same way again. To multiply, a cell splits into two identical copies. The cell uses the instructions on its DNA and the chemicals in the cell to produce an identical DNA copy for the new cell. Then the process repeats itself many times as one cell copies to become two.

And two copy to become four. And so on. To make organs and tissues, the cells use the instructions on their DNA to build tiny machines. They control reactions between chemicals in the cell that eventually produce organs and tissues.

The tiny machines are proteins. Gene expression relies on helper molecules. One important group of those helpers is known as RNA. The second step, called translation , takes place outside of the nucleus. All human proteins are chains with different combinations of 20 amino acids. Some proteins control chemical reactions. Some carry messages. Still others function as building materials.

Other chapters in Help Me Understand Genetics. Genetics Home Reference has merged with MedlinePlus. Learn more. The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.

How do genes direct the production of proteins? From Genetics Home Reference. Topics in the How Genes Work chapter What are proteins and what do they do? In addition to specifying the amino acid methionine, it also serves as the start codon to initiate translation. The reading frame for translation is set by the AUG start codon. The genetic code is universal. With a few exceptions, virtually all species use the same genetic code for protein synthesis.

The universal nature of the genetic code is powerful evidence that all of life on Earth shares a common origin. Codons and the universal genetic code.

Ribosomes are able to read the genetic information inscribed on a strand of messenger RNA and use this information to string amino acids together into a protein.

It states that genes specify the sequence of mRNA molecules, which in turn specify the sequence of proteins. The translation of this information to a protein is more complex because three mRNA nucleotides correspond to one amino acid in the polypeptide sequence. Transcription is the first step in gene expression. Some transcripts are used as structural or regulatory RNAs, and others encode one or more proteins.

If the transcribed gene encodes a protein, the result of transcription is messenger RNA mRNA , which will then be used to create that protein in the process of translation. Translation is the process by which mRNA is decoded and translated to produce a polypeptide sequence, otherwise known as a protein. The main function of tRNA is to transfer a free amino acid from the cytoplasm to a ribosome, where it is attached to the growing polypeptide chain. The ribosome then releases the completed protein into the cell.

Privacy Policy. Skip to main content. Genes and Proteins. Search for:.