Birth defects are a heavy blow to the family and a heavy economic burden to the country. Because one’s health is not affected by carrier status, most parents are unaware their “harm” gene until the birth of newborn with defect, which leads to the absence of genetic counseling and preconception carrier testing.
Carrier screening in healthy individuals with no a positive family history can help to testing carrier status for genetic diseases. Carrier screening early screening for genetic diseases with high incidence of ethnic populations in some geographical regions [16, 17]. Since autosomal recessive disorders are more common in certain populations, early screening work was carried out on the basis of race. The international carrier screening program has been carried out for many years, expanding from a single race to a multi-ethnic group, and the types of diseases are gradually increasing, from high-risk groups to low-risk groups.
China is a country with a high incidence of birth defects, with an average of one birth defect every 30 seconds. China is still in the early stage of research and development, and population-based carrier screening has not yet been carried out on a large scale due to limitation of associated harms and costs, especially in ethnic minority. As a minority located in north China for generations with a population of over 120,000, the Daur has their own genetic background so that the genetic characteristics of the Daur nationality are not allow to be neglected. By screening the hot spot mutation of genetic diseases, it can take the initiative to prevent some ethnic genetic diseases and block the chance of genetic diseases in the offspring.
At present, there is no reporting the prevalence of rare genetic diseases of the Daur and describing the attitudes of people towards carrier screening. In the present study, about 400 alleles associated with 11 relative common recessive disease in the Daur population were detected. Carrier frequency in the Daur population was 10.16%. The carrier positive rate of congenital hearing loss, CAH, and PKU were detecting more than 1% in the Daur population. Comparing with the Han population in China, it’s found that the distributions of carrier variation is relatively simple in the Daur (Table 4). Thalassaemia is one of the most common genetic disorders in the world, mainly distributed in coastal areas, and 4.54% and 11.07% of the population in Hunan  and Guangdong  represented heterozygous carriers of α-thalassaemia and β-thalassaemia. Different from the other populations located in the south of China, no individuals were detected with thalassaemia carrier in the Daur population. In addition, genetic deafness is highly heterogeneous, but mutations in the GJB2, SLC26A4, and MT-RNR1 are the majority in diverse populations. However, only mutation c.235 delC and c. 299_300 delAT of the GJB2 gene in 85 related variations were screened positive in the Daur population.
HLD, also known as Wilson’s disease, is another common detected disease with heterozygous carrier in our present study. However, only two variation types were found, ATP7B c.3316 G > A mutation was the most common variants in the Daur population, and another variation was ATP7B c.2621 C > T.
SMA is the most common neuromuscular AR disorder caused by SMN1 mutation, and SMA carrier screening is beneficial to genetic counseling and reduce the number of affected children. ACMG has recommended offering carrier screening for SMA to couples regardless of ethnicity . SAM carrier frequency has been reported as 1 in 72 to 1 in 47, which was different in ethnic. It has been reported that the carrier frequency in China is about 2.2% in Taiwan, 1.6% in HongKong, 1.9% in Shanghai, and 1.2 in Liuzhou population . In 2020, a largest-scale carrier screening for SMA in mainland China showed that 1.77% women were identified as carrier in 13069 women (approximately 1:56 in the population) . However, the frequency of Daur is lower than that of these populations, only one out of 246 individuals was detected to be a positive carrier.
Fragile X is a kind of X-linked disorders, which are due to mutation in genes on the X chromosome. Female carries of an X-linked disorder are at 50% risk for having an affected male newborn and a carrier female newborn. In the present study, we found there was one carrier of Fragile X in the Daur population. According to ACMG and ACOG, Fragile X should be screened based on family history. DMD, a common disease in rare diseases, also is a X-linked disorder, comparing with the treatment, screening test is an effective method to prevention it . In our study, we failed to find one carrier in the Daur population.
Our study has some limitations. First, the carrier frequency is low for many diseases, so it is necessary to expend number of included samples. Secondly, the failure to perform a more in-depth analysis due to the lack of detailed information