Relationship between Genotype and Phenotype Molecular Basis for Relationship between Genotype and Phenotype genotype DNA DNA sequence transcription RNA translation amino acid sequence protein function phenotype organism

Spliceosome Assembly and Function Spliceosome interacts with CTD and attaches to pre-mRNA. snRNAs in spliceosomes direct alignment of the splice sites. One end of conserved sequence attaches to conserved adenine in the intron. The “lariat” is released and adjacent exons are joined. Refer to Figure 8-16 from Introduction to Genetic Analysis, Griffiths et al., 2015.

Colinearity of Gene and Protein genotype DNA DNA sequence transcription RNA translation amino acid sequence protein function phenotype organism

Relationship between Genotype and Phenotype Molecular Basis for Relationship between Genotype and Phenotype genotype DNA DNA sequence transcription RNA translation amino acid sequence protein function phenotype organism

tRNA Refer to Figure 9-6 from Introduction to Genetic Analysis, Griffiths et al., 2015. Anticodon of a tRNA molecule recognizes and pairs with an mRNA codon. tRNA contains modified bases: pseudouridine, methylguanosine, dimethylguanosine, methylinosine, dihydrouridine.

Genetic Code

Aminoacyl-tRNA Synthetase Attaches Amino Acid to tRNA There is an aminoacyl-tRNA synthetase for each amino acid. The carboxyl end of an amino acid is attached to the 3’ end of the tRNA. Compare to Figure 9-7 from Introduction to Genetic Analysis, Griffiths et al., 2015.

Wobble Position Some tRNA molecules can recognize and pair with more than one specific codon. Base-pairing between the 3’ base of a codon and 5’ base of an anticodon is not always exact. Refer to Figure 9-9 from Introduction to Genetic Analysis, Griffiths et al., 2015.

Relationship between Genotype and Phenotype Molecular Basis for Relationship between Genotype and Phenotype genotype DNA DNA sequence transcription RNA translation amino acid sequence protein function phenotype organism

Protein Synthesis: Brief Summary 3 Stages Initiation Elongation Termination Catalytic Proteins Initiation Factors Elongation Factors Termination Factors Hydrolysis of GTP provides energy to drive some reactions. mRNA, rRNA, and tRNA are involved.

Protein Synthesis: Initiation in Prokaryotes Refer to Figure 9-13 from Introduction to Genetic Analysis, Griffiths et al., 2015. Shine-Dalgarno sequence pairs with 16S rRNA of 30S subunit. IF3 keeps 30S subunit dissociated from 50S subunit. Formyl group is added to methionine when associated with the initiator tRNA. IF1 and IF2 allows only initiator tRNA to enter P site. Initiation factors are released when two ribosomal subunits associate. Refer to Figure 9-14, Griffiths et al., 2015.

Initiation in Eukaryotes Protein Synthesis: Initiation in Eukaryotes eIF4A, eIF4B, and eIF4G associates with 5’ end, then with 40S subunit and initiator tRNA. mRNA is unwound by movement of this complex in 5’ -> 3’ direction. 60S subunit associates with initiation complex when start codon is recognized. Initiation factors are released when the two ribosomal subunits associate. Refer to Figure 9-15 from Introduction to Genetic Analysis, Griffiths et al., 2015.

Important Features of Ribosome Refer to Figure 9-12 from Introduction to Genetic Analysis, Griffiths et al., 2015. A - aminoacyl site P - peptidyl site E - exit site

Proteins and RNA Molecules Compose the Two Subunits of a Ribosome Refer to Figure 9-10 from Introduction to Genetic Analysis, Griffiths et al., 2015.

Protein Synthesis: Elongation EF-Tu associates with aminoacyl-tRNA to form a ternary complex. Correct match of ternary complex with codon in A site (decoding center) changes conformation of ribosome. EF-Tu leaves ternary complex, and peptide bond is formed between amino acids as amino acids are positioned together in peptidyltransferase center. Refer to Figure 9-16 from Introduction to Genetic Analysis, Griffiths et al., 2015. Amino acid in P site is transferred to amino acid in A site. Translocation requires GTP and EF-G. EF-G enters A site, shifting tRNAs. When EF-G leaves, A site is open for a new ternary complex. A new ternary complex associates with A site, and deacylated tRNA leaves from E site.

Protein Synthesis: Termination tRNA molecules do not recognize stop codons. Termination codons are recognized by release factors. (RF1, RF2, RF3 in bacteria) UAA and UAG are recognized by RF1. UAA and UGA are recognized by RF2. RF3 assists in release activity. Release factors bind to a stop codon in the A site by association between codon and tripeptide of RF. Polypeptide is released from P site when RF fits into A site. Release of polypeptide is followed by dissociation of ribosomal subunits. Refer to Figure 9-17 from Introduction to Genetic Analysis, Griffiths et al., 2015.