What Is Heredity & How Do We Acquire It? Genetics Made Easy
For those of you who are not quite as genetically inclined, rest assured that heredity is not a genetic condition, although it has something to do with both genetics as well as how conditions are acquired.
Defined most simply, the process by which heredity takes place is the passage of features from one generation to the next. In other words, it is the transfer of traits (both the recessive trait and dominant trait) from mother and father to their child. These traits are passed down because of the genetic material that determines the traits that are inherited by the children from their parents.
Heredity and Cell Division
Traits are manifestations of our genes that are made up of DNA. Genes are located on chromosomes, and most of us have a total of 46 chromosomes or 23 chromosome pairs. Out of those pairs, 22 are autosomes and one is a pair of sex chromosomes. In females, the pair of sex chromosomes is made up of two X chromosomes while males have one X and one Y chromosome.
When a female reproductive cell (ovum) is fertilized with a male reproductive cell (sperm), the next step is cell division. This process is a complex series of events that revolve around the equal distribution of genetic material via chromosomes. In other words, you are the product of your biological mother’s and father’s chromosomes. In other words, half of your genetic material comes from your mother and the other half from your father. Put differently, you inherit half of your traits from each one of your biological parents. The process of cell division that marks the proper distribution of genetic material via chromosomes is called meiosis. This, in turn, is made up of four sub-steps, each of which has a very specific task when it comes to the proper division of genetic material. This is heredity in its broadest sense.
The acquisition of traits from one generation to the next is also called inheritance whereby both parents contribute equally to the offspring’s genetic repertoire.
Before we go further into heredity and inheritance, let us first give homage to the one person who is responsible for most of what we know about genetics and genetic inheritance. Nearly two centuries ago, an Augustinian monk, driven by his love for the life sciences, set out to study inheritance and the way traits are passed down. Gregor Mendel studied almost 30,000 pea plants and pretty much lined out for us the fundamentals of modern biology and genetics as we know it today. The way he went about it was by looking at the traits of the plants he crossed, then observing the characteristics of their offspring. He then crossed the first offspring and observed the characteristics of their offspring. Based on the outward and visible characteristics of those plants, Mendel came up with several laws by which traits are passed down through the generations.
Mendel’s Principles of Inheritance
These include the law of dominance, the law of segregation, and the law of independent assortment. The law of dominance revolves around dominant genes being displayed as outward characteristics, while recessive genes are masked by the traits of the dominant ones. The law of segregation revolves around the segregation of chromosomes during cell division, whereby they are equally distributed from one parent cell among a total of four daughter cells.
An Example of Heredity
The best way to define heredity, however, is through an example.
Imagine a mother who has a daughter and a son, and each of the children needs to have a bedroom that has to be furnished. Luckily, the mother has a “set of twos” for each of the items that she passes on to the children. In other words, one chair to each of them, one bed, and one closet to each one of them. The children now each have exactly half of the mother’s belongings. That is exactly how genetic material is distributed from parents to children during cell division.
Along those lines, the father also has double the bedroom furniture that the children need to equip their bedrooms. Therefore, the father also gives one chair, one bed, and one closet to each of the kids. Now, both the girl and the boy have two of each. Imagine that each of the furniture items is a gene, and each of the doubles is called alleles. So, let’s say that one of the boy’s chair is brown and the other is blue. In other words, the boy has one chair gene, but he has two alleles—one brown and one blue. Imagine now that the chair is a symbol for the eye color gene, whereby the blue allele codes for blue eyes and the brown allele codes for brown eyes. Remember how we talked about Mendel’s law of dominance?
In this case, the dominant eye color gene is brown. In other words, the boy who has two eye color alleles (one brown and one blue) would have brown eyes because the brown allele is dominant over the blue allele. The only time the boy would have blue eyes would be if he had two blue alleles.
So, there you have it. A simple breakdown of inheritance and heredity and how it is passed on from parents to their offspring. Of course, there is a lot more to it than this, but this is a good start toward a better understanding of how genes are passed on, how they manifest themselves, and, ultimately, what makes us who we are inside and out.