Who We Are to Become Begins Long Before Birth

Theme: “Who we are to become begins long before birth.”

Each of us began life as a single cell weighing about one twenty-millionth of an ounce (Santrock 77)! From the moment of conception, all individuals are the same, what happens after this is what shapes us into different special people. We are all composed of DNA, and each of us has completely different strands which make up our unique identity. DNA produces what is known as genes that influence our genetic makeup. These genes get passed down from generation to generation and help shape who we become. How they get passed down can be explained through three processes; mitosis, meiosis and fertilization.

Mitosis is a process in which our cells duplicate themselves and divide into two matching cells with 23 chromosomes. Another type of cell division called meiosis-forms eggs and sperm (Santrock 78). During meiosis, a cell of t testes (in men) or ovaries (in women) duplicates its chromosomes but then divides twice, thus forming four cells, each of which has only half of the genetic material of the parent cell (Santrock 78). So by this time, each sperm or egg has 23 unpaired chromosomes. Next is the fertilization, in which a sperm and egg fuse together to create a single cell, called the zygote, and the 23 unpaired chromosomes come together. Now this new cell has half chromosomes from the mother, and half from the father. So each parent contributes to half of the child’s genetic makeup. The individual chromosomes have major impact on features like sex, hair color, height and weight. Each fused chromosome contains the same feature, but one might be female and the other male. The difference between becoming male or female, is dependent on the pair having two chromosomes called X chromosomes, which would be female, or the pair having an X and Y chromosome, would be male.

What genes are passed down from the mother and father is simply by chance, and the fusing together creates a very unique offspring. All of a person’s genetic material makes up his or her genotype (Santrock 79). However, not all of the genetic material is apparent in our observed and measurable characteristics. A phenotype consists of observable characteristics, including physical characteristics (such as height, weight, and hair color) and psychological characteristics (such as personality and intelligence). For example, an individual can inherit the genetic potential to have a high intelligence level, but the child still needs to be exposed to reading and learning activities throughout infancy to reach full potential. This phenomenon has a name, Heredity-environment interaction, or gene-environment interaction.

So how does it happen that an individual has blonde hair instead of brown hair if both genes were present in the fused chromosome? Well one gene of a pair is known as the dominant gene, which overrides the effect of the other gene known as the recessive gene. If an individual receives two identical recessive genes, the child will show the trait. However, if a child only receives one recessive gene; the trait will not show through. Brown hair, farsightedness, and dimples rule over blond hair, nearsightedness, and freckles in the world of dominant-recessive genes (Santrock 79).

One way to view whether the fetus is developing normally is through a process known as an ultrasound sonography. Ultrasound sonography is a prenatal medical procedure in which high-frequency sound waves are directed into the pregnant woman’s abdomen. The echo from the sounds is transformed into a visual representation of the fetus’s inner structures (Santrock 85). This can be performed seven weeks into pregnancy, and can tell the sex of the child, and if the brain is developing properly. It also gives the new parents a first glimpse of their new child.

Pregnancy is divided into three different stages. First is the germinal period that takes place in the first two weeks after conception. During this stage, the zygote is created and attached to the uterine wall. Next is the embryonic period that occurs two to eight weeks after conception. This is when the organs are starting to appear, and when the umbilical cord is created and attached to the placenta. The final stage is the fetal period, which lasts two months to the end of the pregnancy. Each is prominent in the development of the child. The environment can affect the unborn baby in many ways. First we will talk about a teratogen, which is an agent that can harm the embryo.

Every fetus is exposed to some sort of teratogens, but the dose, genetic susceptibility and the time of exposure to a certain teratogen influence the severity of the damage. The dose would be like a certain kind of drug, the more that is taken in, the greater the effect. The type or severity of abnormalities caused by a teratogen is linked to the genotype of the pregnant woman and the genotype of the embryo of the fetus (Santrock 107). For example, how a mother metabolizes a particular drug can influence the degree to which the drug effects are transmitted to the embryo or fetus (Santrock 107). The time of exposure means what stage the drug was taken in; damage during the germinal period could cause a miscarriage, damage in the embryonic period could cause abnormalities within the limbs. Exposure during the fetal period can stunt growth or create problems with the organs and cause them not to function properly. There are several different types of teratogens, so I will start with prescription drugs.

Although many women are prescribed drugs during pregnancy, they have lifelong affects on the growing fetus. Certain prescribed drugs that can cause the most damage are antibiotics, some antidepressants,

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