Life begins when the fusion of an egg and sperm forms a single cell, which contains the DNA blueprint required to grow and develop into a complex organism. Almost all human cells contain a pair of each of 23 chromosomes--very large stretches of DNA that each contain several genes required for cellular function--one from the mother and one from the father. Each chromosome contains millions of chemicals called nucleotide base pairs, which link together in specific sequences to make up genes. Inherited genetic mutations from parents can lead to the development of serious genetic diseases in babies, which can ultimately prove fatal.
Tay-Sachs Disease
Tay-Sachs is a genetic disease that affects babies and often leads to death. Babies with Tay-Sachs experience neurological defects that manifest as deafness; lack of muscle tone and muscle control; blindness; and eventually, seizure and paralysis, which can prove fatal.
The genetic basis of Tay-Sachs stems from a mutation to a gene on chromosome 15. The Tay-Sachs mutation leads to an inability to break down substances called gangliosides, and the accumulation of gangliosides leads to nerve cell death.
Tay-Sachs is an autosomal recessive disorder, which means that the baby must receive a copy of the mutated gene from both parents. Parents may carry the Tay-Sachs mutation without having the disease. If both parents carry the Tay-Sachs mutation, their child has a 25 percent chance of developing the disease.
Phenylketonuria
Phenylketonuria, also called PKU, is a genetic disease that affects babies. Patients with PKU carry a mutation in the gene PAH, which normally plays a role in breaking down the amino acid phenylalanine. Without a functional PAH gene, phenylalanine accumulates in nerve cells, leading to nerve cell damage and death, reports the University of Utah. Although babies are asymptomatic at birth, untreated PKU leads to massive brain damage. Like Tay-Sachs, PKU is an autosomal recessive disorder. Shortly after birth, babies are tested for blood levels of phenylalanine, and an abnormally high level may be used to diagnose PKU. PKU can be treated by consuming a protein-deficient diet to limit phenylalanine intake, and by avoiding artificial sweeteners that contain phenylalanine.
Fragile X Syndrome
Another genetic disease that affects babies is fragile X syndrome, also called Martin-Bell syndrome. It is the most common cause of inherited genetic mental retardation and impairment, reports the National Fragile X Foundation. It affects both males and females, though the symptoms of fragile X syndrome are typically more severe in males. Patients with fragile X syndrome experience mental disorders such as autism, along with bone and joint abnormalities and heart defects.
Fragile X syndrome is caused by mutation to a gene FMR1, which is found on the X chromosome. Patients with fragile X syndrome have abnormal repeats of small sequences with DNA within the FMR1 gene, which causes the cells to inactivate the gene. Without an active FMR1 gene, cells lack a protein required for proper functioning, which causes the symptoms of fragile X syndrome. The treatment for fragile X syndrome typically includes therapies to treat the symptoms of the disease.
