Mutations Answer Exam

Mutations Worksheet KEY Name There are several types of mutation: DELETION (a base is lost) INSERTION (an extra base is inserted) Deletion and insertion may cause what’s called a FRAMESHIFT, meaning the reading “frame” changes, changing the amino acid sequence. SUBSTITUTION (one base is substituted for another) If a substitution changes the amino acid, it’s called a MISSENSE mutation. If a substitution does not change the amino acid, it’s called a SILENT mutation. If a substitution changes the amino acid to a “stop,” it’s called a NONSENSE mutation. Complete the boxes below. Classify each as either Deletion, Insertion, or Substitution AND as either frameshift, missense, silent or nonsense (hint: deletion or insertion will always be frameshift). Original DNA Sequence: T A C A C C T T G G C G A C G A C T mRNA Sequence: A U G U G G A A C C G C U G C U G A Amino Acid Sequence: METHIONINE -TRYPTOPHAN - ASPARAGINE - ARGININE- CYSTEINE - (STOP) Mutated DNA Sequence #1: T A C A T C T T G G C G A C G A C T What’s the mRNA sequence? A U G U A G A A C C G C U G C U G A (Circle the change) What will be the amino acid sequence? METHIONINE -(STOP) Will there likely be effects? Mutated DNA Sequence #2: YES What kind of mutation is this? SUBSTITUTION - NONSENSE T A C G A C C T T G G C G A C G A C T What’s the mRNA sequence? A U G C U G G A A C C G C U G C U G A (Circle the change) What will be the amino acid sequence? METHIONINE - LEUCINE -GLUTAMIC ACID – PROLINE Will there likely be effects? YES What kind of mutation is this? INSERTION - FRAME SHIFT Mutated DNA Sequence #3: T A C A C C T T A G C G A C G A C T (Circle the change) What’s the mRNA sequence? A U G U G G A A U C G C U G C U G A What will be the amino acid sequence? METHIONINE-TRYPTOPHAN-ASPARAGINE- ARGININE- (STOP) Will there likely be effects? NO What kind of mutation is this? SUBSTITUTION – SILENT MUTATION Mutated DNA Sequence #4: T A C A C C T T G G C G A C T A C T What’s the mRNA sequence? A U G U G G AA C C G C U G A U G A (Circle the change) What will be the amino acid sequence? METHIONINE-TRYPTOPHAN-ASPARAGINE- (STOP) Will there likely be effects? Original DNA Sequence: YES What kind of mutation is this? SUBSITUTION - NONSENSE T A C A C C T T G G C G A C G A C T A U G U G G AA C C G C U G C U G A mRNA Sequence: Amino Acid Sequence: METHIONINE-TRYPTOPHAN-ASPARAGINE-ARGININE-CYSTEINE- (STOP) Mutated DNA Sequence #5: T A C A C C T T G G G A C G A C T What will be the corresponding mRNA sequence? A U G U G G A A C C C U G C U G A What will be the amino acid sequence? METHIONINE-TRYPTOPHAN-ASPARAGINE- PROLINE - ALANINE Will there likely be effects? YES What kind of mutation is this? DELETION – FRAME SHIFT 1. Which type of mutation is responsible for new variations of a trait? FRAME SHIFT AND MISSENSE 2. Which type of mutation results in abnormal amino acid sequence? FRAME SHIFT, NONSENSE, AND MISSENSE 3. Which type of mutation stops the translation of the mRNA? NONSENSE Sickle Cell Anemia Sickel cell anemia is the result of a type of mutation in the gene that codes for part of the hemoglobin molecule. Recall that hemoglobin carries oxygen in your red bloods cells. The mutation causes the red blood cells to become stiff and sickle-shaped when they release their oxygen. The sickled cells tend to get stuck in blood vessels, causing pain and increased risk of stroke, blindness, damage to the heart and lungs, and other conditions. Analyze the DNA strands below to determine what amino acid is changed and what type of mutation occurred. Normal hemoglobin DNA Normal hemoglobin mRNA C A C G T G G A C T G A G G A C T C C T C G U G C A C C U G A C U C C U G A G G A G Normal hemoglobin A.A. sequence VALINE-HISTIDINE-LEUCINE-THREONINE-PROLINE-GLUTAMIC ACIDGLUTAMIC ACID -------------------------------------------------------------------------------------------------------------------------------Sickle cell hemoglobin DNA Sickle cell hemoglobin mRNA C A C G T G G A C T G A G G A C A C C T C G U G C A C C U G A C U C C U G U G G A G Sickle cell hemoglobin A.A. sequence VALINE-HISTIDINE-LEUCINE-THREONINE-PROLINE-VALINEGLUTAMIC ACID Point mutations - alter a single base – base substitution mutations – substitute one base for another – nonsense mutations – create stop codon – frameshift mutations – caused by insertion or deletion of a single base – -triplet repeat expansion mutations involve a sequence of 3 DNA nucleotides that are repeated many times Chromosomal mutations change the structure of a chromosome – deletions – part of chromosome is lost – duplication – part of chromosome is copied – inversion – part of chromosome in reverse order translocation – part of chromosome is moved to a new location Substitution – silent mutation. If there was no effect on the protein coded by the gene, then the amino acid sequence must have been the same as the original sequence. Therefore the mutation must have been a substitution resulting in a codon that encoded the same amino acid as the original amino acid. Methionine and Tryptophan have only one codon. All other amino acids have more than one codon. TEF ATC ATE TET HER AT This sentence no longer makes sense. This is an example of a deletion resulting in a frame shift. The first 28 amino acids will be correct. # 1 and # 3 have the same amino acid sequence, therefore they code for the same protein A frameshift mutation is more likely to result in a nonfunctional protein. A frame shift mutation results from an insertion or a deletion, alters the sequence of bases in codons at the mutation and after the mutation. This changes the amino acid sequence and the resulting protein. A point mutation could be a silent mutation, maintaining the original amino acid sequence and the resulting protein.