When does a pattern form between the species of an organism and the number of chromosomes that it has? Why does the number of chromosomes change? These two questions are the reasoning for my research and I have found some very interesting data to answer them. Scientists around the world have been trying to explain the reasoning behind the varying numbers of chromosomes that species have acquired throughout history. Scientist all have their own interpretation of the evidence, therefore they have different phrasing behind their explanations, but all evidence points to mutation. This is how all evolution works. Depending on the mutation the number of chromosomes can increase or decrease. In organisms like humans, every chromosome comes in a pair. This is also known as a “diploid organismâ€.
.An example of a mutation is when anaphase is occurring and the chromosomes are being separated to be shared between the parent and the daughter cell.If an extra chromosome is created by mutation problems can occur, a grouping of three chromosomes can not be separated equally. The end result of this is one of the two cells having an extra chromosome. Two things could happen from here, either the cell is unaffected and the number of chromosomes has increased or the cell is defective and problems occur for the organism. The name for this is trisomy and a prime example of this is a common disease in humans called down syndrome. This is when the 21st chromosome is copied an extra time and instead of there being a total of 46 chromosomes there are now 47.
The number of chromosomes does not have to increase for a mutation like this to occur. Chromosomes can also “disappearâ€, an example of this is when humans evolved from apes. An ape has 48 chromosomes and a human only has 46. How could it be that two chromosomes became one? The answer lies in the humans second chromosome. This chromosome is unique to humans because it is the product of fusion between two chromosomes that are separate in other primates. There is strong evidence to prove that the two chromosomes fused together. For example the chromosome normally has one centromere. This is the center point at which two identical chromosomes are joined together. In the human chromosome there are inactive remnants of a second centromere.
Although in my research I was not able to find a definitive answer for my first question of a pattern between the different numbers of chromosomes. I was able to answer how they were created or “lostâ€. After my analysis of the subject, I believe that mutation is how the number of chromosomes changes in different species and there is more than one way that chromosomes can be added or lost. For example the DNA of the organism could become mutated and the cell fuses or creates chromosomes not strictly by mutation, but by following the genetic code in its DNA. The research I did showed me very interesting characteristics of chromosomes and how they are formed, but I am certain I have only scratched the surfaces of the biology behind them.
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