What is the difference between enantiomers and diastereomers?
These are both types of stereoisomers. Enantiomers are two molecules that are non-superimposable mirror images of each other. This means that every chiral carbon in the molecule has inverted stereochemistry. Due to this, enantiomers have the same physical and chemical properties. Diastereomers do not have the same physical and chemical properties. Diastereomers are two molecules that have inverted stereochemistry at one or more of their chiral carbons, but not all of them.
In a protein that contains the amino acid aspartic acid, which other amino acid can be substituted for the aspartic acid residue and have the least negative effects on the overall protein function and shape?
Substituting the amino acid glutamic acid for the aspartic acid residue in this protein would have the least negative side effects on the overall protein. Aspartic acid and glutamic acid differ by the addition of one carbon molecule, therefore they are very similar in size, charge and structure. They are both polar, acidic amino acids and have the same chemical groups. Therefore, they will have the same types of interactions with other molecules. When glutamic acid is put in the place of an aspartic acid residue, there will be no change in overall charge or interactions in the protein and therefore it should be able to fold and function correctly.
What are the different types of point mutations possible during DNA replication and which is the most harmful?
Although DNA polymerase has proofreading ability, there are still many errors that can occur during DNA replication and base pairing. A silent mutation occurs when DNA polymerase makes an incorrect basepair, but the resulting codon still codes for the same amino acid as the original codon. Therefore, this has no effect on organism. A missense mutation is one in which the base pair change results in the input of a different amino acid. This can greatly effect the protein created and have effects on the organism. Finally, a nonsense mutation occurs when the base pair change creates a stop codon. This will result is shortening of the overall protein. Usually, the resulting protein is non-functional. Therefore, the nonsense mutation is the most harmful.