Question

1. the first column of this table shows the beginning of a gene and five different mutations of this part of the gene. use the base - pairing rules to complete the second column. for each mutation, write in any mrna codons that will be changed as a result of the mutation and use check marks to indicate codons that will not be changed.

beginning of gene in dna	first five mrna codons	beginning of protein
original dna = tacgcaagtacctga...	aug cgu uca ugg acu	met - arg - ser - trp - thr
mutation 1 = tacgccagtacctga... (nucleotide change underlined)
mutation 2 = tacgca_cgtacctga... (nucleotide change underlined)
mutation 3 = tacgcaagtac_ttga... (nucleotide change underlined)
mutation 4 = tacgaagtacctga... (second c deleted)
mutation 5 = tacgcaagtactga... (third c deleted)

Explanation:

Step1: Recall base - pairing rules for DNA to mRNA

DNA: A pairs with U, T pairs with A, C pairs with G, G pairs with C. Each set of 3 mRNA nucleotides is a codon.

Step2: Analyze Mutation 1

Original DNA: TACGCAAGTACCTGA...; Mutated DNA: TACGCCAGTACCTGA...
mRNA for original: AUG CGU UCA UGG ACU; mRNA for mutated: AUG GGU UCA UGG ACU.
Changed codon: CGU -> GGU.

Step3: Analyze Mutation 2

Original DNA: TACGCAAGTACCTGA...; Mutated DNA: TACGCA[C]GTACCTGA...
mRNA for original: AUG CGU UCA UGG ACU; mRNA for mutated: AUG CGU UGA UGG ACU.
Changed codon: UCA -> UGA.

Step4: Analyze Mutation 3

Original DNA: TACGCAAGTACCTGA...; Mutated DNA: TACGCAAGTAC[TT]GA...
mRNA for original: AUG CGU UCA UGG ACU; mRNA for mutated: AUG CGU UCA AUG ACU.
Changed codon: UGG -> AUG.

Step5: Analyze Mutation 4

Original DNA: TACGCAAGTACCTGA...; Mutated DNA: TAC[GAA]GTACCTGA...
mRNA for original: AUG CGU UCA UGG ACU; mRNA for mutated: AUG CUU CAU GGA CU.
Changed codons: CGU UCA UGG ACU -> CUU CAU GGA CU.

Step6: Analyze Mutation 5

Original DNA: TACGCAAGTACCTGA...; Mutated DNA: TACGCA[AG]TACTGA...
mRNA for original: AUG CGU UCA UGG ACU; mRNA for mutated: AUG CGU UAG UGG ACU.
Changed codon: UCA -> UAG.

Answer:

Beginning of gene in DNA	First five mRNA codons	Beginning of Protein
Mutation 2 = TACGCA[C]GTACCTGA...	AUG CGU UGA UGG ACU (UCA changed to UGA)	Met - Arg - stop - Trp - Thr
Mutation 3 = TACGCAAGTAC[TT]GA...	AUG CGU UCA AUG ACU (UGG changed to AUG)	Met - Arg - Ser - Met - Thr
Mutation 4 = TAC[GAA]GTACCTGA...	AUG CUU CAU GGA CU (CGU UCA UGG ACU changed to CUU CAU GGA CU)	Met - Leu - His - Gly - (frameshift mutation affects rest of protein)
Mutation 5 = TACGCA[AG]TACTGA...	AUG CGU UAG UGG ACU (UCA changed to UAG)	Met - Arg - stop - Trp - Thr