Genetics : Recessive Trait

Genetics : Recessive Trait

By : Sudhamsh

Genetics is the study of genes and alleles and how they are passed on. When we are dealing with regular [Mendelian] genetics, we would ONLY have 2 types of alleles : Dominant and recessive. The words themselves are self-explanatory, one is dominant over the other while the other being recessive. We will focus on the recessive gene because people sort of naturally believe that it is not as useful to learn about it. But, there are fascinating things about recessive which, I think, happened so much by chance. Otherwise, we would have all had a particular gene in EVERY single human.

Things to know : 

                     1) Recessive is always masked by dominant.

                2) Having a recessive trait is rare, considering 95% of the time it is masked by the dominant gene.

                     3) Represented by lower-case letters when working with regular genetics.

                     4) Recessive does NOT mean you don't have the disease/ trait [sometimes].

                     5) Dominant alleles are NOT better than recessive alleles.

Summary : As we saw in the 4th bullet point above, I said : Recessive does NOT mean you don't have the disease/ trait because some diseases only occur when there is a recessive allele present for it. Take for example : Color blindness, it is a recessive disease which ONLY happens when you have all recessive alleles to make the disease happen. Because in males, there is only 1 x-chromosome [neglecting the y because not much genetic info] and you only need one recessive allele to actually get the disease. So, they are more likely to get recessive diseases or to put it better : they are more likely to get diseases that are X-linked meaning they are linked to the 23rd chromosome pair. In the 5th bullet point, I said dominant is not better than recessive. Consider an example for this one, like say some rock pocket mice have dark fur, and some have light fur. The dark-fur allele is dominant, and the light-fur allele is recessive. When mice live in a habitat filled with dark rocks, dark fur is “better” because it makes the mice less visible to predators. But when mice live in a habitat filled with light rocks and sand, light fur is “better.” It’s the environment that matters, not whether the allele is dominant or recessive. So, it is important to understand what trait and allele is acting on which environment which changes how long they survive. Having a dominant trait when you don't need it is NOT good at all. But, having a recessive trait might just be perfect for that situation. So, just understand that recessive traits are not just being masked by dominant, but they hide a fascinating story behind them.

Source : http://learn.genetics.utah.edu/content/basics/patterns/

Mr. Black's Powerpoint[s]