Genetic Mutations: Substitution and Frameshift Mutations Constants I Periodic Ta

Question

Genetic Mutations: Substitution and Frameshift Mutations Constants I Periodic TablePartA ONA polymemarase makes a ign. If it pults the r the DNA When DNA s replicated the DNA polymerase is very accurate and rarely makes a mistake However, occasionally, the polymerase makes a mistake in the raplication. A mistake made by the DNA palymerase is known as a mutation. If it puts the wrong base n the sequence, the type of mutation ls called a base substitution mutation H the DNA polymerase leaves out a nucleotide or adds an extra nucleotide to the sequence, then the mutation is known as a frameshft mutaian A segmant of DNA has the following sequence of nucleotidas: 5' ACTACGTGA -3 Sort the folowing DNA sequences by the kind of mutations they contain (frameshift or base subsstution), as compared to the original sequence shown above. Sort the items into the appropriate bin. View Available Hintis) Reset Help 5-ACTTACOTGA-T Base substitution mutation Frameshift mutation Part B Generally speaking, which of the folowing types of mutation wouid most severely affect the sequence of the protein coded by the gene? View Available Hinats) Base subettution at the beginning of the gane

Explanation / Answer

Ans. Frameshift mutation is the insertion or deletion of on ‘n’ residues in the reading frame of mRNA, where n is NOT divisible by 3. It thus changes the reading frame of mRNA because the reading frame is shifted by a number not equal to 3 or its multiple – which is the basic unit (triplet codon) of translation.

So, the number of nucleotides in mutated sequence is different (may be more or less) than the original sequence.

# Base substitution: A mutation in which one or more bases are substituted (replaced) by other base.

The number of nucleotides in the mutated sequence is same as that of original sequence.

# So, the correct options are-

#I. Base substitution mutation: Sequence of 9 nucleotides as in original sequence.

            5’-ACTAAGTGA-3’ ,              5’-ACTACGTGT-3’

#II. Frameshift mutation: Mutation sequence is NOT 9 nucleotide long.

            5’-ACTCGTGA-3’ (8 nucleotides);   5’-ACTTACGTGA-3’   (10 nucleotides)

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