Naina B. answered • 05/31/14
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Dear Gloria,
In sixties, the hypothesis was one gene-one polypeptide. However, that concept has completely changed. The central dogma used to be:
Chromosome/DNA to mRNA to protein.
Again that has changed. A gene or a locus can have multiple transcripts that can be tissue-specific or development specific. For instance, oncogenes are turned on early in the development to promote growth through cell-proliferation. They are supposed to stay off during the adult life. Their misregulation induces proliferation that may lead to tumor formation or tumorigenesis.
A locus or gene can produce different RNAs in different cells and different times of organism's life. Therefore, one gene to one polypeptide is not true any more.
Broadly, there are quantitative and qualitative traits that are formed by number of biochemical pathways that come from gene-networks. There are structural genes such as actin and myosin for muscle fibers and there are regulatory genes that turn on or switch off the transcription of such structural genes. There are monogenic traits or polygenic traits. Sometimes a single nucleotide change creates a stop codon resulting in truncated polypeptide or a longer polypeptide due to single nucleotide change in splice site.
Many traits are likely to be polygenic, however, there is classic example of hemophilia. If trait is going to be polygenic or monogenic will depend on the trait as well.
Hope it helps.
