Chapter 9, Problem 1RQ

Summary Introduction

To review:

Methods of DNA (deoxyribonucleic acid) exchange in microorganisms.

Introduction:

Gene transfer is the method by which a foreign gene is inserted into the cell. Bacteria and other microorganisms acquire genes by this method to acquire useful genes. Horizontal gene transfer or lateral gene transfer is the lateral movement of genes between species. It is different from gene transfer in sexual reproduction in which vertical gene transfer occurs. Horizontal gene transfer can occur in three ways: transformation, transduction, and conjugation.

Explanation of Solution

Microorganisms exchange DNA in three ways:

1. Transformation: It is a method of horizontal gene transfer by which some microorganisms take up the genetic material from the environment. This process only requires the presence of DNA in the environment of the cell. The bacterial cell should be competent enough to take up foreign DNA. After entering the cytoplasm, the DNA may be integrated into the chromosome.

2. Transduction: It is a method in which the genetic material from one bacterial cell is transferred to the other cell by a virus. Bacteriophage is the class of virus which infects the bacterial cell. Bacteriophage transfers its genetic material inside the bacterial cell and uses it as a host to make progeny viruses. Later when this bacteriophage infects the new host, a part of the bacterial DNA may get incorporated into the new host.

3. Conjugation: It is the method of transferring genetic material between bacteria through direct contact. The bacteria that donate the genetic material carry a DNA sequence called F-factor or fertility factor. F-factor helps to form a tubular structure called a pilus. The genetic material is transferred to the recipient cell through the pilus.