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What is a gene?

A gene is a part of DNA that carries the information needed to make a protein. People inherit one copy of each gene from their mother and one copy from their father. The genes that a person inherits from his or her parents can determine many things. For example, genes affect what a person will look like and whether the person might have certain diseases.

How many genes do humans have?

It is estimated that humans have between 20,000 and 25,000 genes, although research is ongoing. 

What are genes made of?

Genes are small sections of the very long molecules called DNA. The building blocks of DNA are nucleotides. Each nucleotide contains a small chemical called a base, either the A, C, T, or G base. Each gene is a sequence of these base letters. 

What is a recessive gene?

A recessive gene is the gene that may be masked by a dominant gene. We receive one version of a gene from each parent, which are called alleles. When the alleles are different, the recessive allele will be masked and the dominant allele will be expressed. When we receive two recessive alleles for the same gene, then a recessive allele may be expressed. 

What are linked genes?

The genes that are physically closer together within the same chromosome are considered to be linked genes. Due to their close proximity, they are more likely to be inherited as a unit compared with those that are further apart or not on the same chromosome.

Learn more about Gene:

Photo of Kristin Ricklefs-Johnson

Medically reviewed by:

Kristin Ricklefs-Johnson, Ph.D., RD

Kristin is an RDN who also earned her Ph.D. in Nutrition from Arizona State University with an emphasis on insulin resistance, lipid metabolism disorders, and obesity. She completed her post-doctoral fellowship at Mayo Clinic where she focused on nutrition-related proteomic and metabolic research. Her interests include understanding the exact mechanism of action of various genetic variations underlying individual predispositions to nutrition-related health outcomes. Her goal is to help all individuals prevent chronic diseases and achieve long, healthy lives through eating well.

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