Transcription and Translation Notes for IB Diploma Year 1
DNA is a huge information database that carries the complete set of instructions for making all the proteins a cell will ever need! Although there are only four different bases in DNA (A, C, G and T), the order in which the bases occur determines the information to make a protein, just like the 26 letters of the alphabet combine to form words and sentences: Compare: RAT - TAR - ART - same 3 letters; completely different meanings. And with DNA: GAC - AGC - CGA - same 3 'letters'; completely different meanings to the cell (specifies the amino acids Aspartic Acid, Serine, and Arginine) Q: Review: What are genes?
A: The DNA in each chromosome that DOES provide the instructions for a protein is called a gene. * In the 1940s, scientists proposed, fairly correctly, that each gene "codes for" (contains the instructions for) one protein. This is referred to as the "one-gene, one-protein" hypothesis. * One gene will code for perhaps two or more related proteins. * Scientists realized that we had only about 30,000 genes, coding for 100,000 different proteins - rather than the 100,000 genes that had been estimated for the human genome * The basic hypothesis is still the same, but we know a lot more details. Q: If DNA is in the nucleus and proteins are synthesized in the cytoplasm, on ribosomes and in the RER, how to they "get together"? A: The answer: use a "messenger" to carry the instructions from DNA out into the cytoplasm. A nucleic acid very similar to DNA, called mRNA or messenger RNA, is a copy of a gene, and serves this function the "bridge" between DNA and protein: The Central Dogma:DNA encodes the information to make RNA and RNA molecules function together to make protein
| II. What is RNA and how is it different from DNA?
Two big differences between DNA and RNA:
* 1. The sugar in DNA is deoxyribose; in RNA it is ribose * 2. The nitrogenous base uracil (U) is used in RNA in place...
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