Chapter 17, Problem 1SQ

Summary Introduction

Introduction:

DNA is the genetic material of all organisms except some viruses. DNA replication is the process by which the genetic material of the organism copies itself to be distributed among the daughter cells during cell division. The DNA replication takes place before the cell division and prepares the cell for mitosis and meiosis.

Answer to Problem 1SQ

Correct answer:

Mutation serves as the source for new alleles as they change in the protein structure and gene sequence. Hence, the correct answer is option a.

Explanation of Solution

Reason for correct answer:

Option a. is given as “mutation.”

The mutation is the change in the nucleotide sequence of the gene, which results in either the formation of a defective protein or no protein at all. The mutation can also alter the regulation of certain genes leading to their hyperactivity or hypoactivity. Hence, option a. is correct.

Reason for incorrect answer:

Option b. is given as, “natural selection.”

Natural selection is a progressive evolutionary process which is brought about by the alteration in the inheritable characteristics in a group of individuals or populations over generations. This helps in the differential selection of the species and their reproduction based on the ability to adapt. Hence, option b. is incorrect.

Option c. is given as, “Genetic drift”.

Genetic drift is the alteration in the frequency of a gene variant that exists within a population, because of a random sampling of organisms. Hence, option c. is incorrect.

Option d. is given as, “Gene flow”.

Gene flow is the passing of the genetic characters in the form of genes from one generation to another generation within a population. The gene flow is constant in a population but varies among different populations or communities. Hence, option d. is incorrect.

Option e. is given as, “All are original sources of new alleles”.

The mutation is the new sources of alleles as it changes the genetic sequence of the genetic material while other phenomenon does not bring about the formation of new alleles. Hence, option e. is incorrect.

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

Conclusion

A mutation can lead to the change in the gene sequence, which alters the protein and is the cause responsible for the formation of new alleles. Thus, the correct option is a.