Transcription and RNA Processing: Lecture Notes PDF

1940- Beadle and Tatum: Found that deficiency in an enzyme in Neurospora crassa that resulted in the fungi not being able to synthesize an amino acid was inherited One gene  one enzyme hypothesis (not correct) 1950s and 1960s- Ochoa, Brenner, Jacob,...

1940- Beadle and Tatum: Found that deficiency in an enzyme in Neurospora crassa that resulted in the fungi not being able to synthesize an amino acid was inherited One gene  one enzyme hypothesis (not correct) 1950s and 1960s- Ochoa, Brenner, Jacob, and Meselson: RNA was an intermediate molecule Central dogma The central dogma Replication Transcription The complete DNA molecule is Only some DNA fragments are copied copied Both DNA strands are copied Only one of the DNA strands is copied, not always the same strand for a given DNA molecule DNA RNA Replication Transcription The complete DNA molecule is copied Only some DNA fragments are copied Both DNA strands are copied Only one of the DNA strands is copied, not always the same strand for a given DNA molecule DNA Polymerase RNA Polymerase Needs a template Needs a template Needs a primer Does not need a primer Uses dNTPs as substrates Uses NTPs as substrates Synthesizes in the 5’3’ direction Synthesizes in the 5’3’ direction DNA RNA When a single strand is given for the sequence of a gene, the sequence given is that of the coding strand in the 5’ to 3’ direction from left to right Replication Transcription The complete DNA molecule is copied Only some DNA fragments are copied Both DNA strands are copied Only one of the DNA strands is copied, not always the same strand for a given DNA molecule DNA Polymerase RNA Polymerase Needs a template Needs a template Needs a primer Does not need a primer Uses dNTPs as substrates Uses NTPs as substrates Synthesizes in the 5’ 3’ direction Synthesizes in the 5’ 3’ direction Starts at origins of replication Starts next to promoters Template strand Coding strand Coding strand Template strand Gene- DNA sequences that have all the information necessary for the synthesis of an RNA Processing of pre-mRNA All All except histones mRNAs Many  Alternative splicing One gene  more than one polypeptide  Sequencing of genomes from organisms number of genes is not proportional to complexity of organism ▪ Humans : about 20,000-25,000 genes ▪ Fruit flies: about 14,000 genes Being able to produce more proteins from the same number of genes can add to the complexity of the organisms Alternative splicing results in more proteins from the same pre- mRNA and therefore can result in more proteins and more specific functions without increasing the amount of DNA in the genome