Question

Populations that experience inbreeding may also experience a. a decrease in fitness due to an increased frequency of recessive genetic diseases. b. an increase in fitness due to increases in heterozygosity. c. very little genetic drift. d. no apparent change. e. increased mutation rates.

Short answer

a. a decrease in fitness due to an increased frequency of recessive genetic diseases.

Step-by-step solution

Understanding Inbreeding and Recessive Genetic Diseases

Inbreeding can lead to an increase in the frequency of homozygous genotypes and therefore recessive genetic diseases. If a harmful allele is recessive, it will only have an effect if both the parents carry and pass on this harmful allele. Inbreeding, therefore, can potentially increase the chance of recessive genetic diseases manifesting as both parents could carry the same harmful recessive allele. This can result in a decrease in fitness.

Understanding Inbreeding and Heterozygosity

Heterozygosity is when an individual has two different alleles for a trait. Inbreeding decreases the likelihood of heterozygosity as in an inbred population, the chance of both parents passing the same allele to their progeny is increased. Therefore, inbred populations will likely not see an increase in fitness due to increases in heterozygosity.

Understanding Genetic Drift and Inbreeding

Genetic drift can still occur in populations experiencing inbreeding. Inbreeding does not prevent genetic drift, which can occur with any change in allele frequency in a population from one generation to the next due to chance.

Understanding Inbreeding and Mutation Rates

Inbreeding does not inherently increase mutation rates. Mutations occur due to various reasons such as errors in DNA replication, environmental factors, or random events, but the practice of inbreeding itself doesn't increase their occurrence.

Summing up the impact of inbreeding

Option a: a decrease in fitness due to an increased frequency of recessive genetic diseases is a proper indication of the implications of inbreeding. The remaining options don't reflect the effect of inbreeding accurately.

Key concepts

Recessive Genetic Diseases

Recessive genetic diseases occur when an individual inherits two copies of a harmful allele, one from each parent. Such diseases often remain "hidden" in carriers, meaning individuals who have only one recessive allele do not express the disease but can pass it on to offspring. In populations where inbreeding is common, the likelihood of two carriers mating and producing offspring with recessive genetic diseases increases substantially. This is due to the reduced genetic diversity, which makes it more probable that both parents carry the same recessive traits. The presence of these harmful recessive alleles can lead to a decline in the overall fitness of the population, as affected individuals may experience severe health issues.

Homozygosity

Homozygosity occurs when an individual has two identical alleles for a specific gene. Inbreeding significantly increases the frequency of homozygosity within a population, as close relatives are more likely to have similar genetic makeups.
This increase can be beneficial for certain traits but is often detrimental when it comes to recessive genetic disorders. When recessive alleles stem from both parents, harmful traits are expressed.

• Homozygosity for advantageous traits can sometimes be beneficial.
• However, it often leads to the expression of deleterious alleles, which can result in genetic diseases.

The rise in homozygosity can lead to reduced diversity and resilience within the gene pool, making populations more susceptible to diseases and environmental changes.

Heterozygosity

Heterozygosity represents the genetic diversity within an individual, having two different alleles for a particular gene. This genetic variation is crucial for the survival and adaptability of a population, allowing organisms to better withstand diseases and environmental changes.
Inbreeding, however, typically reduces heterozygosity, as it increases the probability that offspring will inherit the same alleles from both parents.

• High heterozygosity is generally associated with increased fitness and adaptability.
• Low heterozygosity, as seen with inbreeding, can make populations vulnerable to pathogens and changing environments.

Thus, while heterozygosity is desirable for a robust population, inbreeding leads to its decline, potentially compromising the health and survival of future generations.

Genetic Drift

Genetic drift is a mechanism of evolution that results in random changes in allele frequencies within a population. Unlike natural selection, which is driven by adaptability and survival advantage, genetic drift occurs by chance.
Small populations are particularly susceptible to genetic drift; in such populations, even a trivial fluctuation can lead to significant changes over time. Inbreeding can exacerbate the effects of genetic drift by limiting the genetic variance within a population.

• It's not prevented by inbreeding, and its effects can be intensified in inbred populations.
• Random allele losses due to drift can lead to reduced genetic diversity over generations.

In summary, genetic drift can contribute to evolutionary changes but can also pose risks to small, inbred populations by reducing genetic variation.

Mutation Rates

Mutation rates are the frequency at which changes in the DNA sequence occur in a given population or organism. These mutations are one of the sources of genetic variation and can be beneficial, neutral, or harmful.
Despite common misconceptions, inbreeding itself does not directly impact mutation rates. The occurrence of mutations depends on various factors including environmental influences, replication errors, and more.

• Mutations create new alleles within a population, contributing to genetic diversity.
• Inbreeding can affect how mutations are propagated within a gene pool, but not their initial occurrence.

Ultimately, while mutation rates themselves are unaffected by inbreeding, inbred populations may see quicker changes due to the higher likelihood of mutations becoming fixed in a small, homogeneous group.