How Can You Explain The Occurrence Of Birth Defects Caused

Ahow Can You Explain The Occurrence Of Birth Defects Caused By Alter

A. How can you explain the occurrence of birth defects (caused by altered genes) in children and grandchildren of WWII atomic bomb victims, when the victims themselves were only mildly affected? B. During the past 50 years, more than 200 species of insects that attack crop plants have become highly resistant to DDT and other pesticides. Based on what you have learned in this class regarding evolution, explain the rapid and widespread evolution of resistance. Now that DDT has been banned in the US, what do you expect to happen to levels of resistance to DDT among insect populations?

Paper For Above instruction

The occurrence of birth defects in descendants of atomic bomb victims, despite the victims themselves being only mildly affected, can be best explained through the lens of genetic mutations and heritable changes induced by radiation exposure. Radioactivity from nuclear bombs causes ionization of molecules within cells, leading to DNA damage including mutations. While many mutations are neutral or deleterious, some may occur in germline cells—sperm or eggs—making them heritable. These mutations, if affecting developmental genes, could manifest as birth defects in subsequent generations (Little et al., 2014). Importantly, the severity of the initial radiation exposure may not correlate directly with the heritable genetic damage transmitted to offspring. Deleterious mutations accumulated in the germline over time can lead to new genetic disorders that surface in grandchildren, even if the original victims exhibited only mild radiation effects. Hence, heritable genetic changes caused by radiation are a critical factor explaining the increased incidence of birth defects across generations, independent of the immediate somatic effects seen in the survivors (Durante et al., 2007).

Regarding the rapid development of insect resistance to DDT over the past five decades, this phenomenon exemplifies the principles of evolution by natural selection. Insect populations exposed to DDT produce genetic variation in susceptibility owing to existing mutations. Individuals harboring resistant alleles are more likely to survive DDT spraying and pass on these resistance genes to offspring. Over successive generations, this selective pressure results in a shift in allele frequencies, leading to widespread resistance. The high reproductive rates and short generation times of insects accelerate this evolutionary process, enabling resistance to become prevalent within decades (Tabashnik & Carrière, 2017). The widespread use and environmental persistence of DDT further amplified this selection pressure, enabling rapid resistance development across multiple species.

However, since DDT has been banned in the United States since the 1970s, the selection pressure maintaining resistance is largely removed. Without continued exposure, resistant insects face a disadvantage compared to susceptible ones due to potential fitness costs associated with resistance genes—such as reduced reproductive capacity or slower development. Over time, these fitness costs may lead to a decline in the frequency of resistance alleles within insect populations. Empirical studies have observed such reversion in resistance levels after cessation of DDT use, indicating that resistance traits can diminish in the absence of selective pressure (Roush & Tabashnik, 1990). Therefore, if DDT use remains discontinued, it is expected that resistance among insect populations will gradually decrease, ultimately restoring susceptibility to effective levels.

In conclusion, heritable genetic mutations resulting from radiation exposure in WWII atomic bomb victims explain the increased birth defects across generations despite mild initial effects. Simultaneously, the evolution of insect resistance to DDT exemplifies how selective pressures can rapidly drive genetic changes—a process that reverses when those pressures are removed. Studying these phenomena provides profound insights into genetics, evolution, and environmental health, emphasizing the importance of understanding heritable mutations and selective forces shaping biological diversity (Grant & Grant, 2019).

References

Durante, M., et al. (2007). Cardiac and neurological effects of radiation exposure. Journal of Radiation Research, 48(2), 101-108.

Grant, P. R., & Grant, B. R. (2019). Evolutionary dynamics of Darwin’s finches. Proceedings of the National Academy of Sciences, 116(41), 20464-20473.

Little, M. P., et al. (2014). Genetic consequences of the atomic bombings in Hiroshima and Nagasaki. Proceedings of the National Academy of Sciences, 111(9), 3302-3307.

Roush, R. T., & Tabashnik, B. E. (1990). Pesticide resistance in insects: biology, genetics, and management. CRC Press.

_TABASHNIK, B. E., & CARRIÈRE, Y. (2017). Resistance management in pest insects. Insects, 8(4), 81.