Congenital Birth Defects Essay -- Genetic Causes, Chromosomal Abnormal

1.1 Congenital Birth Defects Birth defects, congenital abnormalities are terms used to describe developmental defects that are present at birth. There are a lot of genetic and environmental interactions in the complex transition from a fertilised ovum to a fully formed human being. The stage of development that the interactions are affected influences the type of birth defects. Birth defect causes can be divided into two types, genetic and environmental causes. There are also birth defects which are caused due to multifactorial inheritance (George, 2007). Genetic causes of birth defects It has been estimated that 25% of all birth defects are caused due to genetic factors and out of these 85% causes are known (Brent, 2004). Birth defects can be caused due to chromosomal aberrations, mutations in single genes and interactions of both environmental and genetic factors. Chromosomal aberrations are seen frequently as the complex mechanisms such as meiosis or mitosis are prone to error. Another frequent causative factor of multiple birth defects is chromosomal aneuploidy (loss or gain of whole chromosome). Multiple congenital anomaly syndromes are caused due to single gene defects (Prescott, 2001). Chromosomal abnormalities They may be numerical or structural and are important causes of approximately 5-6% of all birth defects (Young, 2005). These abnormalities may arise newly or maybe inherited from a parent with same chromosomal aberration. Numerical abnormalities are caused due to any deviation from the human diploid number of 46 chromosomes which is called chromosomal aneuploidy. This leads to multiple birth defects as it disturbs the action of multiple genes. Usually, numerical chromosomal abnormalities are resu... ...Synthetic lethality does indicate that when two genes have the same role and mutation occurs in them both making them non-functional only then it results in lethality. Moreover when both the genes have the same function in the pathway, each mutation in the genes diminishes the function of the pathway. Even though genome sequencing of mouse and humans are completed the function of a major part of the genomes are still unknown. An effective way to discover the gene function is by determining the consequence of mutations in organisms. This study focuses on congenital birth defects by studying the mutations in mouse genome causing developmental abnormalities which serve as models for human congenital birth defects. In this study an attempt is made to identify the genes that cause developmental defects and lethality thus aids the study of congenital birth defects.