The tumor suppressor gene p53 is involved in sensing DNA damage and preventing c
ID: 60683 • Letter: T
Question
The tumor suppressor gene p53 is involved in sensing DNA damage and preventing cell replication if the damage is extensive. Below is a partial sequence of the p53 gene. In one particular portion of this sequence, a simple transition can cause a nonsense point mutation. Transcribe and translate the given DNA sequence and clearly indicate what mutation would be required and where it would have to occur. What effect would you expect this transition to have on the organism’s fitness, and why?
3’ TAC GGT ACC CGA GAT TTT ATA TGT 5’
Second UUU Phe UCU Ser UAU Tyr UGU Cys UUC Phe UCC Ser UAC Tyr UGC Cs UUA Leu UCA Ser UAA Stop UGA Stop UUG Leu UCG Ser UA G Stop UGG Trp CUU Leu CCU Pro CAU His CGU Arg CUC Leu CCC Pro CAC His CGC Arg CUA Leu CCA Pro CAA Gln CGA Arg CUG Leu CCG Pro CAG Gln CGG Arg AUU lle ACU Thr AA U Asn AGU Ser AUC lle ACC Thr AAC Asn AGC Ser AUA lle ACA Thr AAA Lys AGA Arg AUG Met ACG Thr AAG Lys AGG Arg GUU Val GCU Ala GAU Asp GGU Gly GUC Val GCC Ala GAC Asp GGC Gly GUA Val GCA Ala GAA Glu GGA Gly GUG Val GCG Ala GAG Glu GGG GlyExplanation / Answer
If the base substitution of one with another results in the formation of a stop codon like UAG, the translation process terminates at that point and the resulting protein is short and may be non functional. These types of mutations are known as nonsense mutations.
Here, the given DNA sequence is in 3' to 5' direction, so it is being considered as template strands. Thus, the coding strand sequence of the given DNA will be, 5' ATG CCA TGG GCT CTA AAA TAT ACT 5'.
Its mRNA sequence is, 5' AUG CCA UGG GCU CUA AAA UAU ACU 5'.
Substituting Uracil (U) with guanine (G) transforms UAU to UAG, UAG is a stop codon. 5' AUG CCA UGG GCU CUA AAA UAG ACU 5'.
The mutated sequence cannot code for p53, means the tumor suppressor activity will be lost in the organism due to this nonsense mutation, the organism will be more liable to generate cancer cells.
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