1. 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

2. 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.

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

4. 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

5. 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.

6. Genetic Code

7. 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.

8. 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.

9. 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

10. 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.

11. 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.

12. 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.

13. 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

14. 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.

15. 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.

16. 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.