Variation plays a vital role in human survival. Variation occurs in the process of meiosis. Meiosis is the process in which human sex cells, called gametes, are produced. Meiosis starts with a parent cell, called a diploid, replicating its DNA. After the DNA is replicated, the chromosomes line up in the middle of the cell where each pair touches each other and genetic information from the alleles are shuffled and exchanged, a process called crossing-over.
The crossing-over over of chromosomes results in what is called recombination, where genetic information from the maternal chromosome (chromosome from the mother) is now on the paternal chromosome (chromosome from the father) or vice versa. Crossing-over and recombination is what causes genetic variation, reshuffling of the chromosomes and then exchanging genetic information. After the chromosomes are lined up and genetic information is exchanged, the parent cell then splits into two identical daughter cells.
The two daughter cells have 23 sets of chromosomes, totaling to 46 chromosomes in all, which is the same amount of chromosomes as the parent cell. Unlike the parent cells, the daughter cells do not replicate their DNA. Instead the chromosomes are split into four haploid cells, the gametes. The gametes are similar to the parent cell but they are not identical, each being unique from one another. The gametes only contain half of the chromosomes as the daughter cells, totaling to 23 chromosomes with no pairs.
One gamete only contains 23 chromosomes because it will then get paired with another gamete during sexual reproduction where even more variation will occur being that those two paired gametes will then reshuffle and exchange their genetic information. (Larsen, 2008) This constant shuffling of genetic information between gametes is the source of variation. Variation is key to survival. If there is no variation, every living thing will be born the same. Larsen, 2008) For example, the peppered moths that live in Great Britain. The color of the peppered moths vary. Some peppered moths were born “peppered”, being all white with black speckles, and some are born completely black.
The peppered moths potentially would have been wiped out during the Industrial Revolution, when the pollution in the air caused the trees to turn black and it was hard for the white speckled moths to blend into the trees. Larsen, 2008) The black peppered moths were able to blend into the darkened tress, making it easy to camouflage themselves against being eaten by birds. Variation amongst the peppered moths saved them from being non-existent. This shows how variation is important amongst humans as well, all being born different with different traits that can or cannot be advantageous. (Larsen, 2008) Variation amongst the population is headed toward a limited future. One example of variation becoming limited is due to designer babies.
Designer babies is a term used to describe a procedure in which parents actually pick the genes their child will have before they are born. This is done by doctors screening embryos. As the embryos are screened, doctors can select the desired sex of the baby that the parents want and they can also search for any genetic disorders and then choose the healthy embryos that are free of genetic disorders to be developed into a “healthy” baby (Design-A-Baby? , 2002).
Although this may sound like a very positive thing for parents that want a certain sex of a baby or also give them the confidence that their baby will come out free of any genetic disorders that may have had a negative effect on their families past, doctors can also screen embryos and choose babies that have genetic disorders that parents actually want them to have such as deafness. (Jabr, 2013) Taking a look at the deaf community shows a limit on variation. Being that I spent a great amount of time around the
Deaf community, I personally saw how the Deaf community intentionally puts a limit to variation amongst their community. Reading on the website blogs. scientificamerican. com about the deaf couple Sharon Duchesneau and Candy McCullough, who desperately wanted to have a Deaf child brought me back to when I first heard about Deaf people actually wanting their children to be born deaf. (Jabr, 2013) | initially thought “why would they want their child to be born with a disability? ” being that I had no idea about Deaf culture.
As time went on and the more I learned about Deaf people and their culture it became totally clear to me as to why they want would want to have deaf children. They do not view their Deafness as a disability, they view their Deafness as a culture. When a deaf couple has a child that is born hearing, whether he/she can hear completely or even have slight hearing, there is a bit of disappointment from the parents and also to the rest of the Deaf community. This disappointment comes from them knowing that the hearing child will not have such a strong Deaf culture being that they will be a part of both the Deaf and hearing communities.
They are very proud of their deafness and they really believe in passing their deafness on to their children in order to keep their Deaf culture alive generation after generation. In the process of learning about variation, it became clear that the Deaf community actually does limit variation amongst their community. Just as Sharon Duchesneau and Candy McCullough searched for a deaf sperm donor to increase the chance to have a deaf baby, couples may actually get to easily choose this specific gene, as well as other genes, through designer babies.
As parents get more and more specific on what they want their “perfect child” to be born as, variation is being limited. Of course no parent wants their child to be born with any life threatening diseases, but if parents do not allow their children’s genes to mutate naturally, more and more humans are going to be born with similar genes. As our genes become more similar to one another, variation amongst the population will decrease.
