Why Some DNA sequence can code for more than one protein?

One reason for this is that there are 20 different amino acids in proteins but only four nucleotides in DNA, so genes that are unrelated usually appear to be more different from one another when their amino acid sequences are compared (Figure 7.10).

How do viruses express genes?

Viral genomes are expressed from mRNAs that are either the nucleic acid of positive-sense [(+)-sense] ssRNA viruses or transcripts from negative-sense [(–)-sense] or dsRNA or from ds or ss DNA viruses.

How many nucleotides are in a virus?

Size of the DNA viruses is larger than that of RNA viruses. Few DNA viruses can be as large as 305,000 nucleotides. DNA viruses are called large viruses and RNA viruses are small. Size of a few single stranded RNA genomes is up to 31,000 nucleotides.

How are viral proteins synthesized?

Viral Proteins These proteins have been synthesized by ribosomes linked to the endoplasmic reticulum. Then, the Golgi system is used to insert the proteins into the plasmic membrane and therefore called late proteins due to their synthesis latency during the viral cycle (Webster et al., 1992).

Can one gene encode more than one protein?

A single gene can produce multiple protein sequences, depending on which exons are included in the mRNA transcript, which carries instructions to the cell’s protein-building machinery. Two different forms of the same protein, known as isoforms, can have different, even completely opposite functions.

What is transcription in viruses?

Abstract. Genome transcription is a critical stage in the life cycle of a virus, as this is the process by which the viral genetic information is presented to the host cell protein synthesis machinery for the production of the viral proteins needed for genome replication and progeny virion assembly.

What is the term used to describe viral nucleic acid surrounded by a protein shell?

A complete virus particle, known as a virion, consists of nucleic acid surrounded by a protective coat of protein called a capsid. These are formed from identical protein subunits called capsomeres. Viruses can have a lipid “envelope” derived from the host cell membrane.

How are viruses different from cells?

Cells are the basic units of life. Cells can exist by themselves, like bacteria, or as part of a larger organism, like our cells. Viruses are non-living infectious particles, much smaller than a cell, and need a living host to reproduce. The genetic material of the cell is DNA, a double stranded helix.

How does protein relate to viral replication?

Viruses cannot replicate on their own, but rather depend on their host cell’s protein synthesis pathways to reproduce. This typically occurs by the virus inserting its genetic material in host cells, co-opting the proteins to create viral replicates, until the cell bursts from the high volume of new viral particles.

How do viruses encode proteins?

Viruses are non-living and do not have the means to reproduce on their own, instead depending on their host cell’s resources in order to reproduce. Thus, viruses do not code for many of their own viral proteins, and instead use the host cell’s machinery to produce the viral proteins they require for replication.