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Name: D J Ferri
Status: N/A
Age: N/A
Location: N/A
Country: N/A
Date: Around 1993


Question:
We are studying genetics and we cannot find a description of a "gene." We have figured that the term is used metaphorical for the part of the DNA molecule that encodes the information for one trait. Is this correct?



Replies:
In the broadest sense of the term, gene refers to discrete heritable factors that encodes for a particular trait. Specifically, a gene is "a segment of a DNA molecule that contains all the information required for synthesis of a product (polypeptide chain or RNA molecule), including both coding and non-coding sequences. It is the biological unit of heredity, self- reproducing, and transmitted from parent to progeny. Each gene has a specific position (locus) on the chromosome map. From the standpoint of function, genes are conceived of as structural, operator, and regulatory genes." - Dorland's Illustrated Medical Dictionary, 27th ed. So, in terms of morphology, a gene is a specific sequence of nucleotide in DNA which encodes for a specific product. This DNA sequence is TRANSCRIBED into an RNA sequence, which is then TRANSLATED through the function of ribosomes to a polypeptide.

wizkid


I am sorry that your texts do not describe the structure of a gene, but many do. Try a college level Introductory Biology text like Campbell, Keeton, or Curtis. First of all, a gene does not encode the information for one trait. It does encode the information for one RNA sequence, which then usually is used to produce one protein. The one protein can then cause changes in many traits of the organism it is in. As stated in the above answer, a gene is a sequence of nucleotide that encodes a single protein. The structure of genes is varied and intensely researched. Almost all genes have 3 major parts, the promoter, the encoding region, and the stop codling. The promoter is a sequence of nucleotide that the RNA polymerase (an enzyme that builds RNA while reading DNA) binds to start transcription. Transcription of a gene into RNA involves reading the nucleotide sequence of the DNA of the gene and creating a copy of it in the RNA form. This RNA form contains information for one protein, unlike DNA strands which contain information for thousands. The encoding region is the largest part of the gene usually. Groups of three nucleotide make up a codling, which codes for one amino acid in the chain that will make up the protein. In eukayotes (all living things besides viruses, bacteria, and cyanobacteria) there are non- encoding regions interspersed in the coding regions. These are called introns and the coding regions call exons. Intron regions are skipped by the RNA polymerase and do not contribute to the RNA made. The final part of a gene is the "stop codon." This a another three nucleotide sequence that tells RNA polymerase to stop right there. There are other parts of genes too called enhancers, operators, CAP biding sites, and the TATA box. Look up "operon hypothesis."

booga



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