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Kelly Valentine Kelly Valentine
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A month ago
describe the genetic and environmental influences on prenatal development;
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A month ago
Prenatal development is the process that occurs during the 40 weeks prior to the birth of a child, and is heavily influenced by genetics and environmental factors.

There are three stages of prenatal development — germinal, embryonic, and fetal. Prenatal development is also organized into trimesters: the first trimester ends with the end of the embryonic stage, the second trimester ends at week 20, and the third trimester ends at birth.

The environmental factors that influence prenatal development include: viruses, diseases, chemicals, drugs, and radiation. Let's focus on drugs and chemicals.


A teratogen is an environmental substance or agent — biological, chemical, or physical — that can have a detrimental effect on a developing fetus. Exposure to teratogens during the prenatal stage can significantly raise the risk of birth defects. Several factors influence the amount of damage a teratogen can have, including dose or level of exposure, heredity, age of the teratogen, and any other negative influences (for example, several teratogens or a teratogen combined with poor health). There are several known teratogens that expectant mothers are advised to avoid during pregnancy, including alcohol, prescription and/or illegal drugs, and tobacco.


Alcohol and most drugs cross the placenta and affect the fetus. Alcohol use during pregnancy has been found to be the leading preventable cause of mental disabilities in children in the United States. Excessive maternal drinking while pregnant can cause fetal alcohol spectrum disorders (FASD) with life-long consequences for the child, ranging in severity from minor to major. It is unknown how much alcohol is necessary to cause damage, and so doctors typically recommend that alcohol should be completely avoided during pregnancy. Physically, children with FASD may have a small head size and abnormal facial features. Cognitively, these children may have poor judgment, poor impulse control, higher rates of ADHD and learning issues, and lower IQ scores. These developmental problems and delays persist into adulthood. Based on studies conducted on animals, it also has been suggested that a mother’s alcohol consumption during pregnancy may predispose her child to like alcohol.

In terms of genetics, we inherit our traits from our genes present in the nucleus of the cell. These genes are encoded in DNA which makes up the 46 chromosomes inherited from both parents at conception, and arranged in 23 pairs. In addition, our genes form pairs; if both genes are dominant in the pair, the individual would display the specific trait. If one gene is dominant and the other is recessive, then the dominant one will show as the child's phenotype. If both are recessive, than the recessive trait will show. Depending on the unique combination a child inherits, it will dictate many things, including one's appearance, health, and other characteristics.
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