NEET Solved Paper 2017 Question 28
Question: If there are 999 bases in an RNA that codes for a protein with 333 amino acids, and the base at position 901 is deleted such that the length of the RNA becomes 998 bases, how many codons will be altered?
Options:
A) 333
B) 1
C) 11
D) 33
Show Answer
Answer:
Correct Answer: D
Solution:
- To determine how many codons will be altered due to the deletion of a base at position 901 in an RNA sequence, we need to understand the impact of this deletion on the reading frame of the RNA.
-
Initial RNA Sequence: The RNA has 999 bases, which code for 333 amino acids (since each amino acid is coded by a codon of 3 bases).
-
Deletion at Position 901: When the base at position 901 is deleted, the total number of bases becomes 998. This deletion causes a frameshift mutation, meaning that the reading frame of the RNA will be altered from the point of deletion onwards.
-
Impact of Frameshift: A frameshift mutation changes the grouping of the bases into codons from the point of mutation to the end of the RNA sequence. Therefore, every codon from position 901 to the end of the RNA will be altered.
-
Number of Codons Affected:
- The deletion occurs at position 901.
- The total number of bases after deletion is 998.
- The number of bases from position 901 to 998 is 98 bases.
- These 98 bases would normally form 32 codons (since 98 / 3 = 32 with a remainder of 2).
Since the frameshift affects all codons from the point of deletion to the end of the RNA, the number of codons altered is 33 (32 full codons plus the codon that includes the 901st base).
BETA
