Who Do You Look Like?

Have you ever wondered why your mom has brown eyes, your dad blue eyes, and you have green eyes? I know what you are probably thinking, “Is that even possible?” Well, in biology we can analyze and predict the probability that offspring will inherit certain characteristics or traits from their parents, all the way from the genetic or cellular level. Before we start, remember that in the reproduction of cells, daughter cells come out identical to their parent cells. However, with us humans, who are multicellular organisms, there is always something that differentiates from our parents.

In human reproduction, the sperm of the father fertilizes the ovum of the mother in order to begin the process that will give shape to who you will become. After spending nine months in the mother’s womb, a really cute and small human being will birth and the question that everyone will ask themselves will be, “Who does he or she look like?” In the process of human reproduction and of almost all living organisms there exists a transference and combining of specific genetic traits and characteristics residing in our DNA that will define head-shape, eye-color, body-size, body-shape, and will practically define all that you will be in spirit, soul, and body. By analyzing these genes in the different generational lines we are able to identify, or at least predict what the next generation will look and be like.

Certain scientists have studied these phenomena and have come to very accurate conclusions that have given an open door to more research that has expanded knowledge to a broader and greater level in the areas of genetic inheritance and reproduction. The first of these scientists was Gregor Mendel who tested the inheritance of pea plants. What this man found was that in reproduction there exist two types of traits, a dominant and a recessive. The dominant trait will be the one that defines about 75% of the characteristics and traits of the offspring. For example, your dad has brown hair and your mother red hair and we want to predict what type of hair color the child will have, well, it will all depend on which of the parents has the dominant and recessive traits. Let’s say the brown hair is the recessive and the red is dominant. In this, we will use a model called Punnet Square to come to the conclusion that there will be a 75% chance of the child having red hair.

The sperm and the ovum are gametes or the cells involved in the reproduction of human beings and each gamete from the parents has one allele and when these gametes fuse together in reproduction, they form the child. Each trait of a child is determined by an allele, which is a specific version of a gene, and a gene is the one that controls the characteristics of the offspring. Now, the child will have two alleles, or specific versions of genes, by inheriting only one from each parent and will exhibit the traits of the dominant allele, in this case, the red hair from the mother.

If you read my essay titled, “The Reproduction of Cells”, you will notice that the process used for cellular reproduction is called Mitosis. In human reproduction and in the great majority of organisms, however, the process of reproduction occurring at the cellular level is called Meiosis. Meiosis is very similar to mitosis with some exceptions, for example, in Meiosis the daughter cells will not be genetically identical and the process of cell division that occurs here, divides in two phases, Meiosis I and Meiosis II.

Most multicellular organisms have two sets of chromosomes that have a copy of one allele in each and are used in reproduction. The two sets of chromosomes are called a diploid. In meiosis segregation occurs, and the diploid is divided and reduced to one set of chromosomes, also known as a haploid. When the gametes carrying now one set of chromosomes of both father and mother fuse together in the fertilization process of reproduction, the two half sets of chromosomes (one half of the father and the other from mother) will restore in a new cell or zygote that will have two alleles newly formed, where the offspring will, in time, express the dominant traits of the dominant alleles or genes in father or mother.

The father and mother, each also contains two sets of alleles they can be heterozygous, where they have one dominant and one recessive allele, or homozygous, where they have two dominant alleles. By knowing which kind of alleles each parent has, we can use two kinds of models called Punnet Squares and Pedigree, with which we can predict what trait the child will exhibit or phenotype and what disease it might carry in his or her DNA. As I said before the child will usually have a three to one probability of exhibiting certain phenotypes.

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