ABSTRACT
To understand the principles of genetic engineering it is necessary first to review the composition and functions of the cell. Living organisms can be divided into two major groups, prokaryotes and eukaryotes. There are several basic differences between these two groups, which are represented, in part, in Table 1 and Figure 1. Schematic of prokaryote and eukaryote cells. The fundamental structural difference of these two cell types lies in the absence of a nucleus in the prokaryote and in the pronounced difference in cell size. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780203753699/85a9a6bc-cc25-40df-b58d-669bc048989c/content/fig2_1_OB.tif"/> Characteristics of Organisms
Feature
Prokaryote
Eukaryote
Structural unit
Bacteria, algae
Unicellular organisms, multicellular plants and animals
Size
<1–2 × 1–4 μm
>5 μm in width or diameter
Location of genetic material
Nucleoid, chromatin body, or nuclear material (different names for same area in which DNA is concentrated)
Nucleus, mitochondria, and chloroplasts
Chromosomes
1
>1
Nuclear membrane
Absent
Present
Histones
Absent
Present
Nucleolus
Absent
Present
Mitochondria
Absent
Present
Chloroplasts
Absent
Present
Golgi apparatus
Absent
Present
Endoplasmic reticulum
Absent
Present
Ribosomes
70S structure
80S structure
Site of electron transport
Cell membrane
Organelles
Genetic exchange mechanisms
Conjugation (plasmid-mediated, unidirectional)
Gamete fusion
Transformation
Transduction
