Chapter 03

Chapter 03 - Chapter 3 Gene Function (DNA - RNA -...

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Gene Function (DNA -- RNA -- polypeptide) •Overview •RNA is transcribed using the rules of base pairing from the template strand of DNA. •Most genes code for protein or untranslated functional RNAs used in protein synthesis. •The nucleotide sequence of the gene determines the order of amino acids in a protein, which determines shape, size, and protein function. •mRNA is translated in groups of three nucleotides (codon) at the ribosome through pairing of tRNA anticodon with the mRNA codon. •Change in nucleotide sequence (mutation) may cause change in amino acid sequence, altering function. •Transfer of information •DNA ® RNA ® polypeptide •Complementary base pairing transfers information –during transcription to form RNA –during translation between codon and anticodon •DNA binding proteins –recognize double- or single-stranded DNA –recognize specific nucleotide sequences –are coded by genes –have variety of important functions •RNA •Transcription: copying nucleotide sequence of DNA into RNA –forms RNA transcript –DNA may be transcribed multiple times •RNA –single-stranded polynucleotide –contains ribose sugar –contains the pyrimidine uracil (U) •hydrogen bonds with A –5’ and 3’ ends critically important •Classes of RNA •Informational RNA: protein encoding mRNA –primary transcript in prokaryotes –processed transcript in eukaryotes •5’ and 3’ end modification •intron removal –translated into amino acid sequence •Functional RNA –tRNA: transport amino acid to ribosome –rRNA: structural and catalytic component of ribosomes –snRNA: structural and catalytic component of spliceosome snRNPs –scRNA: direct protein traffic in cytoplasm •Transcription •RNA polymerase –locally unwinds DNA –uses one DNA strand as template •same strand for a given gene –adds free nucleotides to growing RNA strand at 3’ end
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Chapter 03 - Chapter 3 Gene Function (DNA - RNA -...

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