Question

1. In the absence of folate-fortified foods, is it possible that mutations in the pathway of folate synthesis could cause Spina Bifida?

2. What are the possible advantages or disadvantages to the organism or its offsrping resulting from DNA modification by environmental factor?

Answer 1

Answer =1

Dissecting Genes and Environment in Spina Bifida

Spina bifida (SB) is one of the most common and most complex birth defects involving the nervous system. It occurs with a frequency of 1–2 per 1,000 births in the United States but is higher in other populations. SB is one of a group of disorders called neural tube defects. The neural tube forms early in embryonic development and gives rise to the brain and the spinal cord. Neural tube defects occur during days 17 and 30 of development (the embryo is about the size of a grain of rice at this time) often before a woman realizes she is pregnant. Diagnosis usually occurs by ultrasound during week 15–17 of development. SB is a highly variable disorder, ranging from stillbirth to a form only discovered in apparently normal individuals by X-ray. Many affected individuals have nervous system problems that cause muscle imbalance resulting in crippling deformities and varying degrees of paralysis. In addition, most SB individuals have learning disabilities and may have bladder and bowel problems.

Family and twin studies show that SB has a significant genetic component. It is a complex trait with significant environmental components; nutrition is a key factor. As with other complex traits, it is not clear whether SB is caused by a few rare genes (>10) each of which has a major effect, or is caused by many common genes (<100), each of which has a small effect. One gene associated with SB has been identified. This gene, VANGL1 (MIM 610132), normally controls the movement of cells during development. Mutations in this gene may cause abnormalities in neural tube formation, but how often this happens is not yet known.

Research has shown that nutrition, especially the amount of folate in the diet has a significant impact on the frequency of SB. Folate is a vitamin found in green, leafy vegetables, peas, and beans. It is essential for the formation of new cells, and is important for normal development. How folate and related molecules such as vitamin B12 exert their effects is not well understood, but experiments show that folate causes chemical modifications to DNA that, in turn, change patterns of gene expression.

A diet rich in folate has been shown to reduce the incidence of SB by about 70% and reduces the severity of defects when they do occur. In the United States, grain products have been fortified with folic acid since 1998. Women of childbearing age should eat a folate-rich diet to reduce the risk of having a child with spina bifida.

In the absence of folate-fortified foods, is it possible that mutations in the pathway of folate synthesis could cause SB?