The whole of a person's DNA, called the genome, consists of components called nucleotide bases. The bases link together to form a series of base pairs, and the sequence of base pairs codes for thousands of genes required for growth and survival. Genetic diseases in babies are mutations passed on from the parents. There are a number of causes for genetic diseases in babies, which arise from different types of genetic mutations or mistakes. Each broad type of mutation or mistake can lead to a number of genetic diseases in babies.
Chromosome Trisomy
A person's DNA is divided into large sections, called chromosomes. Most of the cells of the body contain two sets of 23 chromosomes, for 46 chromosomes total. Babies inherit each set of 23 chromosomes from the parents--one set of 23 from the mother and one set from the father. In certain cases, either the mother or father may pass on an extra copy of a chromosome leading to trisomy, resulting in a child whose cells contain 47 chromosomes instead of 46.
A genetic disease in babies caused by this kind of genetic abnormality is Down syndrome. This genetic disorder occurs when a child contains three copies of chromosome 21, instead of two. Screening for down syndrome may occur while the child remains in utero, either through genetic testing or examining the fetus for physical symptoms of down syndrome. Either the mother or the father can pass on the extra chromosome, though the University of Utah reports that the mother provides the extra chromosome in 90% of cases.
Chromosome Deletions
Another cause of genetic disease in babies includes chromosome deletions. Each chromosome contains a series of genes, and abnormalities within the chromosome of the parents' egg or sperm lead to missing genes in the resulting child. Genetic deletions may involve the loss of a single gene if a very small part of the chromosome becomes lost, or the loss of several genes due to deletion of a large part of a chromosome. Merck states that chromosome deletion often leads to very severe developmental disorders, and the baby will face severe mental and physical retardation.
An example of a genetic disease in babies caused by chromosome deletions is cri du chat syndrome, a disorder caused by the deletion of part of chromosome 5. Babies with cri du chat syndrome have a very low birth weight and abnormal craniofacial features, as well as severe mental and physical retardation later in life.
Point Mutations
Another cause of genetic diseases in babies are point mutations. Genes code for specific proteins within the cell, and the sequence of base pairs in the gene corresponds with the makeup of the protein. In a point mutation, a base pair within a gene becomes mutated. This leads to a change in the resulting protein, which may render the protein dysfunctional. Point mutations that change protein function can cause genetic diseases in babies.
A genetic disease affecting babies that results from a point mutation is type 2 Gaucher disease, a disease that results in the accumulation of fatty substances within cells. Babies with Gaucher disease experience progressive brain damage, accompanied by seizures and difficulty sucking or swallowing. According to a study published in Pediatric and Developmental Pathology in 2000, specific genetic point mutations that affect a protein called glucocerebrosidase lead to severe cases of Gaucher syndrome that cause neonatal death.
