Chapter 17, Problem 1SQ

___ is the original source of new alleles.

1. a. Mutation
2. b. Natural selection
3. c. Genetic drift
4. d. Gene flow
5. e. All are original sources of new alleles

Summary Introduction

Introduction: Every organism consists of genes that are made up of DNA. All organisms appear different from one another and also from their ancestors as a result of evolution. Mutation is the key for evolution and the original source for the appearance of new alleles.

Answer to Problem 1SQ

Correct answer: Mutation is the original source of new alleles.

Hence, the correct answer is option a.

Explanation of Solution

Reason for correct answer:

Mutation is a process where a change in the DNA content is inherited to the offspring. Mutation is an alteration in the sequence of an organism's DNA. Mutations can be harmful, but they are sometimes beneficial. They play a vital role in the evolution of an organism or its population. Each and every new genetic trait in an organism will appear as a result of the mutation. This new allele formed as a result of mutation is passed to another through reproduction. Newly formed genetic variant helps an organism to evolve and adapt to unfavorable conditions.

Option a. is given as “Mutation”. Mutation alters the genomic content of an organism and thereby produces new alleles of genes.

Hence, the correct answer is option a.

Reasons for the incorrect answer:

Option b. is given as “Natural selection”. Natural selection is a process where an organism survives an adverse condition by adapting to it. Natural selection does not produce new alleles in organisms, but it takes place after the organisms undergo mutation to adapt to that environment.

Hence, option b.  is incorrect.

Option c. is given as “Gene flow”.  Gene flow is a process where the genes are transferred from one population to another. Gene flow usually carries out the transfer of genetically varied allele. Therefore, it is not involved in the formation of new allele, but only in transferring it.

Hence, option c.  is incorrect.

Option d. is given as “Genetic drift”. Genetic drift is a process where the frequencies of the allele change over generations in a population due to sampling errors. Therefore, it is not involved in the formation of new allele, but only in the measures of change.

Hence, option d. is incorrect.

Option e. is given as “All are original sources of new alleles”. Mutation is the main source of formation of new alleles of a particular gene. This statement is incorrect because all of the above given terms do not lead to form new alleles.

Hence, option e. is incorrect.

Hence, options b., c., d., and e. are incorrect.

Conclusion

Mutation is the original source of new alleles and helps in natural selection and evolution.