Question

By itself, which of the following is not likely to have a major influence on allele frequencies? a. natural selection b. genetic drift c. mutation d. inbreeding e. either \(c\) and \(d\)

Short answer

d. inbreeding

Step-by-step solution

Analyze Each Option

Analyze each option individually. Natural selection is a process where certain traits become more common in a population due to survival advantage they confer, therefore it influences allele frequencies. Genetic drift refers to random changes in allele frequencies, which has a profound influence especially in small populations. Mutation, referring to changes in DNA that create new alleles, can introduce new alleles in the population, influencing allele frequencies.

Analyze Inbreeding

Inbreeding does not generate new alleles or significantly affect allele frequencies. Rather, it influences genotype frequencies by increasing homozygosity. Thus, on its own, inbreeding is less likely to have a major influence on allele frequencies.

Analyze Option E

Option E suggests either mutation or inbreeding could be less influential. However, we've established that mutation does affect allele frequencies by introducing new alleles, rendering option E incorrect.

Key concepts

Natural Selection

Natural selection is a fundamental concept in biology. It is the process where certain traits become more prevalent in a population because they offer some survival or reproductive advantage. When individuals with advantageous traits are more likely to survive and reproduce, these traits become more common in the population over time. This process directly influences allele frequencies, which are the relative frequencies of different forms (alleles) of a gene within a population. Some key points about natural selection:

• It favors beneficial alleles and increases their frequency.
• Harmful alleles are reduced as they often decrease survival chances.
• It can lead to adaptations, which are traits that improve an organism's ability to survive and reproduce.

Natural selection is a powerful force because it actively changes the genetic makeup of a population in response to the environment.

Genetic Drift

Genetic drift is a mechanism of evolution that involves random changes in allele frequencies from one generation to the next. These changes are not driven by natural selection and are often more pronounced in small populations. Unlike natural selection, which is a non-random process, genetic drift is entirely random. It can lead to the loss of genetic variation in a population and, occasionally, unexpected allele frequencies. Here are some important aspects of genetic drift:

• It's more significant in smaller populations, where chance events can have a larger impact.
• It can result in the random loss or fixation of alleles over time.
• Genetic drift can lead to genetic bottlenecks, where substantial reductions in population size alter allele frequencies.

Understanding genetic drift is crucial because it helps explain why populations may evolve differently even when subjected to similar environmental pressures.

Mutation

Mutation is the source of all genetic diversity. It refers to changes in the DNA sequence that can create new alleles in a population. Mutations can be caused by various factors, including errors during DNA replication and exposure to environmental agents like radiation. Mutations have several key roles in evolution:

• They are the original source of all new genes.
• Mutations introduce new genetic variations into a population.
• These changes can lead to new traits that may be advantageous, neutral, or harmful.

While mutation rates are generally low, their effects on allele frequencies can be significant over long periods, especially if coupled with other evolutionary processes like selection.

Inbreeding

Inbreeding occurs when closely related individuals breed with one another. It increases the probability of offspring inheriting two copies of the same allele from an ancestor. This leads to increased homozygosity within the population. Unlike natural selection or mutation, inbreeding doesn't create new alleles or directly alter allele frequencies. Instead, it affects genotype frequencies and can result in inbreeding depression. Some effects and characteristics of inbreeding include:

• Increased likelihood of genetic disorders due to recessive alleles becoming more prominent.
• Reduction in genetic diversity, as genetic variations are less likely to be passed on.
• Potential negative impacts on population fitness and survival.

Despite not affecting allele frequencies directly, inbreeding can influence the long-term genetic health and viability of populations.