Cells that have stopped cycling, such as muscle and nerve cells, are said to be in a special state called G0. G1 phase (gap 1) is a period of cellular growth preceding DNA synthesis.Gene expression occurs throughout all stages of interphase. Interphase describes the time between 2 cell divisions or mitoses. The M phase (mitosis) is the time in which the cell divides to form 2 daughter cells. The concept of the cell cycle can be used to describe the timing of some of these events in a eukaryotic cell. DNA replication is the process in which each chromosome is duplicated before cell division. When cells divide, each daughter cell must receive an accurate copy of the
If the RNA molecule is a messenger RNA, then the process known as translation converts the information in the RNA base sequence to the amino acid sequence of a protein. Transcription, the first stage in gene expression, involves transfer of information found in a double-stranded DNA molecule to the base sequence of a single-stranded RNA molecule. Gene Expression and DNA Replication Gene expression and DNA replication are compared below. Although this definition is now complicated by our increased appreciation of the ways in which genes may be expressed, it is still useful as a working definition. Classically, a gene is a unit of the DNA that encodes a particular protein or RNA molecule. Ultimately, during the process of gene expression, this information is used to synthesize all the proteins made by an organism. Genetic information is stored in the base sequence of DNA molecules. The major steps involved in handling genetic information are illustrated by the central dogma of molecular biology. An organism must be able to store and preserve its genetic information, pass that information along to future generations, and express that information as it carries out all the processes of life.
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