Question

Use the Mutations interactive to determine which statements describe silent mutations. The adenine of the start codon is position +1.

Wild-type Help Template strand (DNA) т | | C | C |G|T Transcription AUG C AU UGG ACGC AUGU U UGC G A G A mRNA Translation Met His TIP Thr Cys Leu Arg STOP Polypeptide chain Mutated Template strand (DNA) TAC GT CTCCT CT Transcription Translation Substitution Addition Deletion Drag tools from the toolbar to mutate the bottom strand of DNA, then click the Transcription arrow. Reset

a substitution from G to T in the arginine codon of the antisense stand

a substitution of a G nucleotide at position +9 in the antisense strand

a transition at position +6 in the sense strand

a transversion of A in the histidine codon of the antisense strand

a single nucleotide deletion at position +12 in the antisense strand

a G nucleotide insertion at position +2 in the sense strand

Answer 1

Silent mutation is a type of point mutation where a single base change in the DNA doesnt affect the amino acid sequence of the protein and therfore do not affect the function of the protein.

a substitution from G to T in the arginine codon of the antisense stand.

Antisense is the strand used as template for mRNA synthesis which directs from 3' to 5 '

Substitution from G to T in the antisense strand makes it AGA in the mRNA strand. AGA codes for Arginine.

So its a silent mutation.

a substitution of a G nucleotide at position +9 in the antisense strand

substitution of C in the +9 position of antisense strand to G makes the codon in mRNA strand to be UGC instead of UGG. UGG codes for trp but UGC codes for cysteine. SO its not silent mutation

a transition at position +6 in the sense strand

Transition is a mutation where a purine gets interchanged for another purine or a pyrimidine gets interchanges for a pyrimidine.

So transition of A in position +6 changes it into G making the mRNA stand s codon to change from CAU to CAC. Both CAU and CAC codes for histidine. SO it is silent mutation.

a transversion of A in the histidine codon of the antisense strand

Transversion is the interchange of a purine for a pyrimidine and vice versa

Transversion of A can be either T,U or C

The codon for histidine is CAU. Transversion can amke it either CUU (leucine) or CCU (proline).So it is not a silent mutation, it is a missense mutation

a single nucleotide deletion at position +12 in the antisense strand

Deletion of C in the +12 position in the antisense strand changes the complete sequence that is after this deletion position in the amino acid sequence. This is not a silent mutation, Because deletion of a basepair in the antisense strand leads to frameshift mutation in the amino acid sequence.

a G nucleotide insertion at position +2 in the sense strand

Sense starnd is complementary to the antisense strand and same as the mRNA strand except for U basepair instead of T.

Insertion also has the same effect as deletion mutation. It causes frameshift mutation changing all the amino acids in the rest of the gene

SO it is not a silent mutation