Tut 10 - Mutations (Teacher)

St Andrew’s Junior College Genetics & Inheritance / Gene mutation & Chromosomal aberration 2021 H1 Biology 1 Full Name: Civics group: 21S Index no.: Date: Core Idea 2: Genetics & Inheritance Gene mutation & Chromosomal aberration Tutorial 10 MCQ ANSWERS 1 2 3 4 5 6 7 A D C D B D C 1 A point mutation is a change to a single nucleotide and can occur anywhere in a gene. Which statements are true? 1 A point mutation in an exon can result in a different amino acid sequence. 2 A point mutation in an exon can produce a shorter protein if a stop codon produced. 3 A point mutation in an intron can alter the binding site of a splicing enzyme. A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only 2 A mutation results in the substitution of thymine for cytosine in the base sequence ATC in a section of a template DNA strand. What are the base sequences on the tRNA corresponding to the new triplet? template DNA: ATC mutant DNA: ACC mRNA: UGG tRNA: ACC (I,e same as mutant template DNA, except U instead of T) A ATC B TAG C UGG D ACC

St Andrew’s Junior College Genetics & Inheritance / Gene mutation & Chromosomal aberration 2021 H1 Biology 2 3 The diagram shows part of the normal sequence of an mRNA molecule. 5’ – CCA AGU GGU CCG CUA AAA UGG C – 3’ Template DNA: GGT TCA CCA GGC GAT TTT ACC G Polypeptide: gly - ser – pro – gly - ??? Mutant DNA: GGT TCA CCA GGC ATT TTA CCG Polypeptide: gly - ser – pro – gly – ile – leu – pro Mutation is a base deletion of 13th nucleotide guanine. A mutation in the DNA resulted in a polypeptide beginning with the following sequence. glycine – serine – proline – glycine – isoleucine – leucine – proline The DNA triplets for some amino acids are Glycine Isoleucine Leucine Proline Serine CGA ATA TTA CCA TCA GGT ATT CTT CCG TCG GGC CTC Which mutation has occurred in the DNA molecule? A A reversal in the order of nucleotide B An addition of an extra nucleotide C The loss of a nucleotide D The replacement of one nucleotide by a different nucleotide 4 Two enzymes X and Y, are each encoded by different alleles of the same gene . The amino acid seqwuences of the two enzymes differ between positions 87 and 91 of the polypeptides. The amino acid sequences of enzymes X and Y, and the corresponding DNA sequence of enzyme X from position 86 to position 93 of the polupeptides, are shown in the table below.

St Andrew’s Junior College Genetics & Inheritance / Gene mutation & Chromosomal aberration 2021 H1 Biology 3 The actual mRNA codons for the amino acids in these positions for enzymes X and Y, are shown in the table below. What could account for the difference in amino acid sequence of enzymes X and Y? A A single frame shift by deletion in the DNA code at position 87. B Frame shift mutations in the DNA codes at position 87 and position 90. C A change in the seq