What is a gene referred to that is absent or turned off due to a mutation that blocks the gene's expression?

What is a gene referred to that is absent or turned off due to a mutation that blocks the gene's expression?

• A. Wild type
• B. Null
• C. Recombinant
• D. Knockin

Answer: (B)

When a mutation stops a gene from being expressed, that gene is called a null allele—a loss-of-function variant in which no functional product is produced. The product is absent or nonfunctional, yielding a null phenotype for that trait. By comparison, wild type is the normal functional allele, recombinant describes DNA assembled from different sources, and knockin means adding a new copy of a gene. So the term that fits an absent or silenced gene due to mutation is null.

When a mutation stops a gene from being expressed, that gene is called a null allele—a loss-of-function variant in which no functional product is produced. The product is absent or nonfunctional, yielding a null phenotype for that trait. By comparison, wild type is the normal functional allele, recombinant describes DNA assembled from different sources, and knockin means adding a new copy of a gene. So the term that fits an absent or silenced gene due to mutation is null.