{'fraction_non_alphanumeric': 0.02561837455830389, 'fraction_numerical': 0.006183745583038869, 'mean_word_length': 5.026595744680851, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Molecular mechanism of recessive congenital methemoglobinemia in Chinese pedigrees.

OBJECTIVE
To investigate the molecular mechanism of recessive congenital methemoglobinemia (RCM) in Chinese and to establish a gene diagnostic method of polymerase chain reaction-restricted fragment length polymorphism (PCR-RFLP).


METHODS
Total RNA was isolated from the peripheral leukocytes of the propositus and b5R cDNA synthesized by reverse transcription-polymerase chain reaction (RT-PCR). The coding region of b5R cDNA was analyzed by sequencing of the RT-PCR products.


RESULTS
Both propositi A and B were found to be homozygotes for a G to A transition at codon 57 in exon 3, changing a guanine to an adenine. This point mutation was not an artificial occurrence during polymerase chain reaction (PCR), as confirmed by Msp I restriction enzyme analysis of the genomic DNA. Propositus A's mother and propositus B's sister and her nephew were found to be heterozygotes for the mutation.


CONCLUSION
A guanine-to-adenine transition at codon 57, replacing arginine with glutamine, was the molecular basis for RCM in two Chinese families.