2. How many different mRNAs could specify the amino acid sequence Met-Phe-Ser-Pro? List them. 3. If the coding region of a gene is estimated to consist of 450 bp, how many amino acids would the corresponding polypeptide chain contain? Estimate the molecular weight of the polypeptide chain (assume the average molecule weight of an amino acid is 110 Daltons). 4. A single base addition and a single base deletion approximately 15 bases apart in the mRNA specifying the protein lysozyme from the bacteriophage T4 caused a change in the protein from its wild-type composition....Lys-Ser-Pro-Ser-Leu-Asn-Ala-Ala-Lys....to the double mutant form....Lys-Val-His- His-Leu-Met-Ala-Lys.... (a) From the mRNA codons in the genetic code (standard codon table), decipher the segment of mRNA for both the original (wild-type) protein and the double mutant (b) Which base was added? (c) Which base was deleted? 5. A eukaryotic cell produces a normal protein with following amino acid sequence: Met-Val-His-Lys-Arg- Thr-Leu-Val. After irradiation, a transformed (mutated) eukaryotic cell is produced that makes a mutant protein from the same coding site on DNA: Met-Val-His-Lys-Glu-Pro. Describe the mutation that occurred. As always, justify your answer. 6. You are working with a newly discovered mutagen, and you wish to determine the base change that it introduced into DNA. Thus far you have determined that the mutagen chemically alters a single base in such a way that its base-pairing properties are altered permanently. In order to determine the specificity of the alteration, you examine the amino acid changes that place after mutagenesis. A sample of what you find is shown below: Original: Gln-His-lle-Glu-Lys Gln-His-Met-Glu-Lys Mutant: 19.
Gene Interactions
When the expression of a single trait is influenced by two or more different non-allelic genes, it is termed as genetic interaction. According to Mendel's law of inheritance, each gene functions in its own way and does not depend on the function of another gene, i.e., a single gene controls each of seven characteristics considered, but the complex contribution of many different genes determine many traits of an organism.
Gene Expression
Gene expression is a process by which the instructions present in deoxyribonucleic acid (DNA) are converted into useful molecules such as proteins, and functional messenger ribonucleic (mRNA) molecules in the case of non-protein-coding genes.
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