Central dogma in the cell DNA is in the nucleus Protein synthesis takes place in the cytoplasm cid 127 mRNA travels in and out of the nucleus transcription to reach both DNA and ribosomes which translate mRNA cid 127 Genotype notes the various sequences present for a gene are the alleles for that gene cid 127 Many sequences can lead it the same phenotype because many of the alleles are loss of function alleles Conceptual Translation All information is stored in DNA and therefore it can be read when the rules are known DNA is transcribed into mRNA cid 127 mRNA is translated into proteins amino acids Rules for transcription cid 127 mRNA is always built from the template strand of DNA cid 127 mRNA is anti parallel to the template strand DNA uses thymine and RNA uses uracil Rules for translation cid 127 mRNA is read in the 5 to 3 direction in codons triplets of bases Reading if mRNA begins at the start codon AUG Codons can be looked up in the genetic code table Reading stops at one of three stop codons Practice DNA strand slide 11 5 Ttt tca gga cac cat gcg 3 template strand 3 aaa agu ccu gug gua cgc 5 Code in the opposite direction Met val ser The template strand is read to synthesize mRNA the coding stand is not read cid 127 mRNA is a copy of the coding strand with all thymine replaced eith uracil Practice slide 17 5 gagatcccttggtacacc 3 coding strand 3 ga gau ccc uug gua cacc 5 mRNA There are three reading frames for a stretch of mRNA cid 127 Which of the first three codons do you begin with cid 127 Once a frame is picked it is set but the correct one will put the stair codon together in a set Frame shift mutation add or remove a nucleotide changes reading frame Impacts of Mutations Point mutation Challenges of Transcription Accurately extract information cid 127 Work with a small piece of a chromosome cid 127 Where to start and stop copying no start or stop codons of ribonucleotides Know when to express a gene Some DNA codes for proteins but a lot more DNA regulates Finding the gene to transcribe Promoter DNA signals that it is near a gene Sigma binds to DNA RNA polymerase finds sigma and begins transcription Unzipping DNA DNA polymerase breaks hydrogen bonds and separates strands DNA polymers bind to template strand RNA polymerase reattaches DNA strands Challenges of Translation Convert information from one format to another cid 127 mRNA folds back on itself and makes a hairpin which breaks off from RNA polymerase and stops transcription cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 Hold everything together in space and time so recognition and bonding can occur cid 127
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