Hyperprothrombinemia is a disorder of prothrombin which leads to hypercoagulation.

Substitution of adenine

Adenine

Adenine is a nucleobase with a variety of roles in biochemistry including cellular respiration, in the form of both the energy-rich adenosine triphosphate and the cofactors nicotinamide adenine dinucleotide and flavin adenine dinucleotide , and protein synthesis, as a chemical component of DNA...

 for guanine

Guanine

Guanine is one of the four main nucleobases found in the nucleic acids DNA and RNA, the others being adenine, cytosine, and thymine . In DNA, guanine is paired with cytosine. With the formula C5H5N5O, guanine is a derivative of purine, consisting of a fused pyrimidine-imidazole ring system with...

 at position 20210 of the prothrombin gene, known as the prothrombin 20210a mutation, prothrombin 20210 mutation and, less precise, just factor II mutation, leads to hypercoagulability and may be a factor that contributes to infertility

Infertility

Infertility primarily refers to the biological inability of a person to contribute to conception. Infertility may also refer to the state of a woman who is unable to carry a pregnancy to full term...

. Its prevalence is thought to be approximately 2% in caucasians and 0.5% in blacks.

Position 20210 falls outside of the reading frame

Reading frame

In biology, a reading frame is a way of breaking a sequence of nucleotides in DNA or RNA into three letter codons which can be translated in amino acids. There are 3 possible reading frames in an mRNA strand: each reading frame corresponding to starting at a different alignment...

 for the protein and is thought to play a role in promoting prothrombin production; the substitution leads to high levels of prothrombin.