Time is really a great phenomenon. It heals old wounds or creates new ones, and is perfectly synonymous with change. When hypotheses are made in science, they are tested with experiments and when they are found to be true by a couple of independent researchers, such hypotheses become theories and when tested widely and found to be true, they become laws. The scientists involved in the formulation and testing of the hypotheses end up etching their names in the history of science.
However, with time, theories or even laws may change or be modified as a result of obvious inconsistencies, telling us that nothing is written in stone in science. This reminds me of the atomic theory that initially postulated that atoms are the smallest, indivisible portion of any substance only for studies to reveal that atoms can later be divided into protons, electrons, and neutrons.
The Mendel's situation
Gregor Mendel is not an unknown man in the science world, especially for his contributions to Genetics and scientific development in general. While the Botanist laid the foundation for many things in science, many of his laws have failed the test of time due to inconsistencies.
Mendel formulated many theories relating to the inheritance of traits from one generation to another through his comprehensive study involving several breeding experiments with the pea plant. In one of his laws known as the law of independent assortment of genes, he postulated that traits are inherited independently of one another. Later discoveries however showed that many of the traits displayed by living organisms are actually a result of the interaction of two or more genes. In other words, what Mendel postulated as the law of independent assortment is more of an exception rather than a general law.
Another of Mendel's laws that seem to have withstood scrutiny until now is the law of segregation. In this law, he opined that each gene coding for a trait is made up of two alternate forms known as alleles. These alleles separate during meiosis and gamete formation. Hence, only one-half (haploid) of the gene is present in every gamete.
During fertilization, a gamete containing one-half of the gene from the male combines with another gamete containing one-half from the female to form the complete gene in the zygote.IN other words, a haploid male gamete fuses with a haploid female gamete to produce a diploid zygote. According to Mendel, the combination/fusion is a random event rather than a structured one. Properly put, Mendel stated that alleles separate during gamete formation and randomly unite during fertilization.
Meiosis takes to produce haploid eggs and sperms in the female and male's human reproductive organs respectively. Since the female is homogametic, the two alleles representing each of the genes within the egg are the same. The male, however, produces different alleles for each gene because of his heterogameity. In other words, the female produces all X eggs while the male produces both X and Y sperms. During fertilization, the X eggs randomly unite with either of the X or Y sperms. An egg fusing with an X sperm would result in a female zygote (XX) while fusion with a Y sperm would result in a male zygote (XY). This is according to Mendel's law of segregation and randomization of fusion.
Why the law may no longer hold true
Findings from a recent study may put the law of segregation and random fusion of gametes in jeopardy. According to the research conducted by scientists from Stockholm University and the Manchester University NHS Foundation Trust, it appears the female egg has the inherent ability to choose which of the sperms (X or Y) would fertilize (fuse with) it.
It was reported that the female eggs produce a signaling molecule into the fluid within the follicle known as chemoattractant with which it communicates with the preferred sperm. On getting to the follicle, the desired sperm picks up the signal and this changes its physiology enabling it to swim faster than the rest of the sperm cells. Concurrently, the chemoattractant slows down the physiology and the swimming ability of the remaining sperms in order to give the desired sperm an advantage in the fertilization race.
If the findings by the researchers are found to be true and widely acceptable to the science world, it will not only put the theory of random union of gametes during fertilization to rest but also poses a major paradigm shift from what we have accepted as norms in genetics. For example, the widely held view in Africa that females are biologically liable in cases where only male or female children are being produced in marriages might hold true. The view has been largely condemned by scientists and labeled a patriarchal one before now but the production of chemoattractant to select which sperm fertilizes the egg would change things.
Also, scientists might be able to manipulate the chemoattractant or produce a counter signaling molecule in order to influence the sperm to be selected for fertilization, thereby being able to pre-select the gender of babies. All in all, another of Mendel's laws may no longer hold true but his works and contributions will never be forgotten in science.
Thank you all for reading.