Using the beta-hemoglobin DNA sequence shown here and the genetic cone provided

Question

Using the beta-hemoglobin DNA sequence shown here and the genetic cone provided in Table 11.1: Explain the changes, if any, that you predict would occur in the mRNA and the amino acid sentence if the following mutations happened to the beta-hemoglobin DNA sequence shown above, and identify the type of genetic mutation involved The second DNA codon, CAG, has a substitution in its first nucleotide, with A replacing C The fifth DNA codon. TGT, has a deletion of the G between its first and second nucleotides. The seventh DNA codon. GAG. has a substitution in its third nucleotide, with T replacing G.

Explanation / Answer

The DNA sequence is: TAC CAG GTA GAC TGT GGG GAG GTT The mRNA sequence is: AUG GUC CAU CUG ACA CCC CUC CAA The peptide sequence is: Met-Val-His-Leu-Thr-Pro-Leu-Glu a. If there is a substitution of adenine with cytosine in the second DNA codon of CAG: CAG codon changes to CCG in DNA while in mRNA GUC changes to GGC. This results in a substitution of glycine for valine. The type of genetic mutation involved is transversion and a point mutation. ------------------------------------------ b. If there is a deletion of guanine in the fifth DNA codon of TGT: This results in a frameshift mutation. The DNA sequence changes in this way: TAC CAG GTA GAC TTG GGG AGG TT The mRNA sequence also changes: AUG GUC CAU CUG AAC CCC UCC AA The peptide sequence is: Met-Val-His-Leu-Asn-Pro-Ser The type of mutation is a deletion which leads to a frameshift mutation. ---------------------------------------- c. If there is a substitution of guanine with thymine in the seventh DNA codon of GAG: GAG codon changes to GAT in DNA while in mRNA CUC changes to CUA. This does not affect the peptide sequence as both the codons code for the same amino acid leucine. This type of mutation is a silent mutation as there is only a change in the genotype but not change in the phenotype of the individual. b. If there is a deletion of guanine in the fifth DNA codon of TGT: This results in a frameshift mutation. The DNA sequence changes in this way: TAC CAG GTA GAC TTG GGG AGG TT The mRNA sequence also changes: AUG GUC CAU CUG AAC CCC UCC AA The peptide sequence is: Met-Val-His-Leu-Asn-Pro-Ser The type of mutation is a deletion which leads to a frameshift mutation. ---------------------------------------- c. If there is a substitution of guanine with thymine in the seventh DNA codon of GAG: GAG codon changes to GAT in DNA while in mRNA CUC changes to CUA. This does not affect the peptide sequence as both the codons code for the same amino acid leucine. This type of mutation is a silent mutation as there is only a change in the genotype but not change in the phenotype of the individual. If there is a substitution of guanine with thymine in the seventh DNA codon of GAG: GAG codon changes to GAT in DNA while in mRNA CUC changes to CUA. This does not affect the peptide sequence as both the codons code for the same amino acid leucine. This type of mutation is a silent mutation as there is only a change in the genotype but not change in the phenotype of the individual.

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