The Jaina Doctrine of Karma And The Science Of Genetics: Chromosomal Abnormalities

Sperm and egg cells are different from other cells is the body. These productive cells have only 23 unpaired chromosomes. When sperm and egg cell unite—and pregnancy begins, they form a fertilized egg with 46 chromosomes.

But sometimes goes wrong before pregnancy begins. In the process of cell division, an error occurs that leaves an egg or sperm cell with too many or too few chromosomes. When this cell with the wrong number of chromosomes joins with a normal egg or sperm cell, the resulting embryo has a chromosomal abnormality. A common type of chromosomal abnormality is called a trisomy. This means that an individual has three copies, instead of two of a specific chromosome. Down Syndrome is an example of trisomy. In most cases an embryo with the wrong number of chromosomes will not survive. In such cases, the pregnant woman has a miscarriage often without knowing it. Upto 70% of first trimester miscarriages are caused by chromosomal abnormalities.^[44]

A person can inherit a genetic disease when one parent (who may or may not have the disease) passes along a single faulty gene. This is called dominant inheritance. Examples include achondroplasia (a form of dwarfism) and Marfan syndrome (a connective tissue disease). Many other genetic diseases are inherited only when both parents (who do not have those diseases) happen to carry the same abnormal gene and pass it on to a child. This is called recessive inheritance. Examples include Tay-sachs disease (a fatal disorder seen mainly in people of European Jewish heritage) and cystic fibrosis (a fatal disorder of Lungs and other organs, affecting mainly Caucasians). There also is a form of inheritance (x-linked) where sons can inherit a genetic disease from a mother who carries the gene (usually with no effect on her own health). Examples include hemophilla (a blood cloting disorder) and Duchenne muscular dystrophy (progressive muscle weakness).

Birth defects also may result from environmental factors such as drug or alcohol abuse, infections, or exposure to certain medications (such as the acne drug accurate) or other chemicals. Many birth defects appear to be caused by combination of one or more genes and environmental factors (called multifactorial inheritance). Some examples include cleft lip/palate, clubfoot and some heart defects.^[45]

Chromosomal abnormalities (numerical or structural alterations) occur from time to time in human beings. The arise in various ways:

1. Non-disjunction
   By an error in nuclear division called "non disjunction" a pair of chromosomes may fail and both are carried to one pole. The resulting daughter cells contain an unequal number of chromosomes 45 to 47. This numerical abnormality in which the chromosome number is not an exact multiple of the haploid number is called aneuploidy. If a particular pair of chromosomes has three chromosomes instead of two, it is called trisomy, if there is only one chromosome instead of two in any given pair of chromosome, it is called "monosomy", non-disjuction may occur during gametogenesis or during mitosis.
   
2. Translocation
   Some time during nuclear division, a portion of one chromosome breaks away and becomes attached to another, which is not homologous to the first. This is called translocation.
   
   
3. Deletion
   A piece of chromosome may become detached and lost from the karyotype resulting in the loss of one or more genes. If the loss is severe, it may be incompatible with live birth.
   
   
4. Duplication
   Some genes may appear twice in the same chromosome. This is called duplication.
   
   
5. Inversion
   Sometimes a chromosomal segment becomes inverted and then the order of sequence of genes is altered.
   
6. Isochromosomes
   These are special class of structurally abnormal chromosomes, arising because of misdivision i.e. transverse division instead of normal longitudinal division.
   
   
7. Mosaicism
   The cells of body are compounded of cells of two or more genetically different chromosomal types. This can result by mutation or non-disjunction either during embryo or later life.

Genes are usually stable, but sometime normal genes may be converted in abnormal ones, this change is called MUTATION. Mutation is a regular phenomenon in nature. The natural mutation rate is increased by exposure to mutagens such as ultraviolet rays, radiation or chemical carcinogens. ^[46]