Some people look like their grandparents because they inherit a similar genetic makeup as that of their grandparents. This has to do with the Law of Dominance.
We’ve all had those moments when someone approaches us at a family party and instantly relates us to our grandparents. There are also times when someone may casually tell you that you don’t look like either of your parents, but then some other time they’ll mention that you look more like your grandmother or grandfather! Well, that sort of resemblance is not uncanny, it’s actually quite scientific. Don’t worry, by the end of this article, you’ll know why!
Our genes contribute to our physical appearance in a major way. Genes are hereditary, which means that they are transmitted from one generation to another, and every individual is a product of its genetic makeup. A human gets its set of genes from both its parents in different combinations. Your parents, in turn, get their genes from their parents. The interesting part is that this transmission doesn’t eliminate any genes at any step. Only the combination varies. Therefore, when your genetic combination resembles that of your grandparents, you end up looking like them, rather than your parents!
What are genes and heredity?
Genes carry the information that determines the characteristics of an individual. Every creature on Earth is a product of its unique genome. In scientific terms, genes are small sections of DNA that contribute to the coding of proteins. They are not haphazardly arranged, but are specific for each protein an organism needs to function. In human cells, the DNA is present on the chromosomes inside the nucleus.
An easy way to understand what genes do is by considering yourself as an example. Are your eyes green? If yes, then either or both of your parents may have green eyes. Do you have blond hair? If the answer is yes, then someone from either your paternal or maternal family must also be blonde. Apart from physical traits, genes are also responsible for the transmission of diseases. A disease called hemophilia, which runs in the family of Queen Victoria, is a prime example of such a condition.
Every organism acquires genetic information from their parents. This passing of traits from parents to their offsprings is called heredity. One can therefore conclude that genes are the functional units of heredity. It is this interplay of genes and inheritance that has resulted in the diverse world we see today. However, the pattern in which genes are inherited may explain we may sometimes resemble our grandparents!
What are the laws of inheritance?
Interestingly, genes are passed from one generation to another in definite patterns. These were studied for the first time by Gregor Johan Mendel. Mendel was initially a priest, but his keen and observant eye pushed him to study the characteristics of pea plants. He spent years studying the differences in their height, the color of their flowers, and the type of seeds etc. based on the pairings of their reproduction. His commendable research gained him the title by which he is now known—The Father of Modern Genetics.
Before diving into the laws of inheritance, let’s take a look at what alleles are. An allele, in the simplest terms, is an alternate form of a gene. Any gene can have multiple alleles. For example, a gene for height will have two alleles, short and tall. A gene for color might also have two alleles, such as red and white. The presence of alleles in a particular combination gives rise to a trait!
According to Mendelian genetics, there are three laws of inheritance. The Law of Dominance states that in a gene, one allele is dominant over the other. This ‘other’ allele is called the recessive allele. Generally, when a pea offspring has one tall allele and one dwarf allele, the offspring turns out to be tall. This means that the tall allele is dominant over the other.
The Law of Segregation says that alleles separate during the formation of the male and female gamete. This means that only one allele for height comes from the father, while the other comes from the mother. These alleles randomly unite when the sperm and ovum fuse. Finally, the Law of Independent Assortment states that alleles of one gene don’t mix with the alleles of another. For example, an allele for height won’t mix with an allele for eye color!
Why do some people look like their grandparents?
Now that you understand the basic laws of inheritance, you may be able to conclude the answer to this article’s question. The Law of Dominance is mainly responsible for such an occurrence. In Mendel’s pea plants, two plants were made to reproduce, a process called a cross. One plant was tall and the other was short. After crossing, the next generation of plants contained only tall plants. One could therefore conclude that the allele for tall height was dominant, and therefore hid the effect of the dwarf allele.
Interestingly, when this generation of tall plants was crossed amongst themselves, the next generation came up with both tall and dwarf plants. How did that happen when both the parent plants were tall? Well, the answer lies in the genes. Even though the previous generation was all tall, the generation did possess the alleles of dwarf height. When recombined, it formed genetic combinations that resulted in both short and tall plants in the new generation. What’s even more fascinating is that this phenomenon happens in well-defined ratios—3:1!
This example can also be related to the case of humans. Even though your parents may look a certain way, their genes still possess their parents’ alleles. In your case, a similar pathway can be observed. The alleles in you must have recombined in such a way that they represent those of your grandparents! This may result in either making you look like them physically, or possibly exhibiting a disease that one of your grandparents experienced.
Basically, the next time someone tells you that you look just like your grandparents, you can blame it on your genes!