Negative Influences on the Developing Fetus

Topics: Allele, Pregnancy, Phenylketonuria Pages: 6 (2174 words) Published: May 10, 2006
Negative Influences on the Developing Fetus

The purpose of this posting is to discuss the maternal / paternal, environmental, and teratogenic factors that have a negative influence on the developing fetus. This information will be related to how it concerns the practice of mental health counseling.

Maternal and paternal factors both affect the developing fetus. According to the reading in Broderick and Blewitt 23 of the 46 chromosomes were contributed by the father so his part can not be down played. With personal experience under the belt of having to boys. It can honestly be stated that during labor and delivery, kind thoughts about their father's role, especially during the painful part, did enter into the equation. Hereditary diseases, according to Broderick and Blewitt, are passed on from parents to children, and the blame could either be a function of normal hereditary processes, or because something went wrong during the production of the ova or the sperm. Disorders can be influenced by recessive, defective alleles, dominant, defective alleles, disorders of polygenic origin, chromosomal abnormalities, and sex-linked disorders.

According to Broderick and Blewitt "many hereditary disorders are caused by recessive. defective alleles, and it is estimated that most people are carriers of three to five such alleles." Most of the illnesses are said to be rare because the individual has to be unlucky enough to have both parents be carriers of the same defective allele, and then to be the one in four (on average) that gets the recessive alleles from both the mother and the father (Broderick & Blewitt, 2006). The disorders that have been traced to recessive gene alleles are; Cystic fibrosis, PKU, Sickle-cell anemia, Tay-Sachs disease, Thalassemia, Hemophilia, and Duchenne's' muscular dystrophy. The last two disorders mentioned are X linked and are expressed primarily or exclusively in males (Table 2.3, p.41). In order to be an good genetic counselor it seems that not only do mom and dad play a large part, but there is also a huge connection to the generations that came before them.

Disorders that are influenced by dominant, defective alleles are related to one defective gene. There are no carriers of such disorders. Anyone who has a defective gene will have the problem, due to the fact that the dominant gene allele is always expressed in the phenotype (Broderick & Blewitt, 2006). If the illness causes the early death of the individual then the illness will die with the victim and not be passed on to the next generation. If the alleles pop up in a future generation it is said to be the product of spontaneous mutation or because of an environmental influence. If the victim does not die during childhood there is always a chance that the dominant, defective allele can be passed from one generation to the next. If one parent has the disease there is a 50% chance that the fetus will inherit this gene from the parent who carries it.

Disorders of a polygenic origin are said to be related to multiple pairs of genes and the combination of defective alleles at several chromosomal sites (Broderick & Blewitt, 2006). The diseases that have been indicated to be of a polygenic nature include; most forms of muscular dystrophy, diabetes, clubfoot, some forms of Alzheimer's disease, and multiple sclerosis (Broderick & Blewitt, 2006). It was stated that genetic effects on behavioral traits are usually polygenic in nature. "This appears to be true for many mental illnesses and behavioral disorders as well, such as alcoholism, criminality, schizophrenia, and clinical depression" (e.g., Charney, Nestler, & Bunnet, 1999; DeAngelis, 1997; Heath et. al., 1997; Plomin, Owen, & McGuffin, 1994).

Disorders caused by chromosomal abnormalities are related to a zygote containing too many, or too few chromosomes. Most zygotes with chromosomal abnormalities are not viable and do not survive. If they do survive, the...
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