Nucleic acids are required for the storage and expression of genetic information.
DNA Structure, Replication, and Repair
OVERVIEW
Nucleic acids are
required for the storage and expression of genetic information. There are two
chemically distinct types of nucleic acids: deoxyribonucleic acid (DNA) and
ribonucleic acid ([RNA], see Chapter 30). DNA, the repository of genetic
information, is present not only in chromosomes in the nucleus of eukaryotic
organisms, but also in mitochondria and the chloroplasts of plants. Prokaryotic
cells, which lack nuclei, have a single chromosome but may also contain
nonchromosomal DNA in the form of plasmids. The genetic information found in
DNA is copied and transmitted to daughter cells through DNA replication. The
DNA contained in a fertilized egg encodes the information that directs the
development of an organism. This development may involve the production of
billions of cells. Each cell is specialized, expressing only those functions
that are required for it to perform its role in maintaining the organism.
Therefore, DNA must be able to not only replicate precisely each time a cell
divides, but also to have the information that it contains be selectively
expressed. Transcription (RNA synthesis) is the first stage in the expression
of genetic information (see Chapter 30). Next, the code contained in the
nucleotide sequence of messenger RNA molecules is translated (protein
synthesis; see Chapter 31), thus completing gene expression. The regulation of
gene expression is discussed in Chapter 32.
Figure 29.1 The “central
dogma” of molecular biology.
The flow of information from DNA to RNA to protein is termed the “central dogma” of molecular biology (Figure 29.1) and is descriptive of all organisms, with the exception of some viruses that have RNA as the repository of their genetic information.
Related Topics
TH 2019 - 2024 pharmacy180.com; Developed by Therithal info.