Question

_________ is the original source of new alleles. a. Mutation b. Natural selection c. Genetic drift d. Gene flow e. All are original sources of new alleles

Short answer

a) Mutation is the original source of new alleles.

Step-by-step solution

Understanding the Question

The question asks about the biological source of new alleles. New alleles refer to variations in genes that arise for the first time.

Analyzing the Options

The options are: mutation, natural selection, genetic drift, gene flow, and all are original sources. We need to evaluate each option based on whether it can generate entirely new alleles.

Evaluating Mutation

Mutation is a change in the DNA sequence of an organism's genome. This change can create new alleles by altering the nucleotide sequence of a gene.

Evaluating Natural Selection

Natural selection is a process where organisms better adapted to their environment tend to survive and produce more offspring, but it does not create new alleles; it only acts on existing genetic variation.

Evaluating Genetic Drift

Genetic drift is a change in the frequency of existing alleles in a population due to random sampling. It does not create new alleles but affects the frequency of existing ones.

Evaluating Gene Flow

Gene flow is the transfer of alleles or genes from one population to another. It introduces existing alleles into a population but doesn't create new alleles.

Considering "All are original sources"

While all options play roles in the diversity and distribution of alleles, only mutation creates new alleles. The other processes act on alleles that are already present.

Identifying the Correct Answer

Since mutation is the only process that can introduce new genetic variations, it is the original source of new alleles. Therefore, the correct answer is 'a) Mutation'.

Key concepts

New Alleles

New alleles are different forms of the same gene that arise due to changes in the DNA sequence. When we talk about new alleles, we are discussing variations that were not present before in the genetic makeup of an organism. These variations are crucial because they contribute to the genetic diversity within a population.

How do new alleles come into existence? The primary mechanism of their creation is through mutations. A mutation is a random change in the DNA sequence of an organism's genome. This change can occur in different ways, such as through errors during DNA replication, exposure to certain chemicals, or radiation.

When a mutation occurs, it can affect a single nucleotide, a part of a gene, or even an entire section of the DNA. These alterations can result in a new allele if they occur in the germ line cells—the cells responsible for generating offspring—which means the change can be passed on to the next generation.

The introduction of new alleles is significant for evolution. Without mutations, populations would lack the genetic variations necessary to adapt to changing environments. Thus, while mutations can sometimes result in neutral or harmful effects, they are also a source of beneficial variations that drive evolutionary change.

Genetic Variation

Genetic variation refers to the diversity in gene frequencies within a population. This variation is critical for a population's ability to adapt and evolve in response to environmental pressures.

Genetic variation arises primarily in two ways. The first is through mutations, which, as we have discussed, introduce new alleles into the gene pool. The second is through sexual reproduction, which shuffles existing alleles during the formation of gametes through processes like meiosis and random fertilization.

Within a population, individuals may carry different alleles for the same gene, leading to differences in traits such as color, size, or resistance to diseases. These traits can be influenced by environmental factors and are subject to processes like natural selection, which acts on the existing genetic variation to favor traits that increase an organism's chance of survival and reproduction.

The importance of genetic variation cannot be overstated: it is the material upon which forces like natural selection and genetic drift act. In a population with ample genetic variation, there is a greater likelihood that some individuals possess traits that confer an advantage under changing environmental conditions. This variation serves as a buffer against extinction and is a fundamental component of biodiversity.

Sources of Genetic Variation

There are several sources of genetic variation that contribute to the diversity of genes within a population. Understanding these sources provides insight into the mechanisms that drive evolution and adaptation.

One of the most significant sources is mutation. As previously mentioned, mutations are spontaneous changes in the DNA sequence of an organism. These changes can create new alleles and bring about unique traits that were not previously present in a population.

Other key contributors to genetic variation include:

• Gene flow: This occurs when alleles are transferred between populations. It can introduce new alleles to a population, increasing genetic diversity.
• Genetic recombination: During sexual reproduction, recombination occurs when chromosomes exchange genetic material during meiosis. This shuffling of alleles results in offspring that have different combinations of genes than their parents.
• Genetic drift: This refers to the random changes in allele frequencies within a population. While it does not create new alleles, it can alter the genetic structure over time, especially in small populations.

Each of these processes contributes to the overall genetic variation within a population. This variation is essential for natural selection to operate effectively, enabling populations to evolve and adapt to their ever-changing environments. Together, these sources ensure that populations are not static and can continually respond to new challenges and opportunities.