DNA Mutations Practice Homework

DNA Mutations Practice Worksheet DIRECTIONS: Transcribe and translate the original DNA sequence. Then, do the same for each mutated DNA sequence. Then, determine the consequence, if any, for each mutation, by circling your choice for each question. You will need a Genetic Code Chart there is one in the lecture slides. Coding Strand (Codons) 5' > > > - - - - - - T T C - - - - - - > > > 3' Template Strand (What is read) 3' < < < - - - - - - A A G - - - - - - < < < 5' mRNA Message (Codons) 5' > > > - - - - - - U U C - - - - - - > > > 3' tRNA Tranfer (Anti-codons)-brings amino acids to the growing protein at the ribosomes Protein Amino Acid DNA 3' < < < A A G < < < 5' Amino > > > Phenylalanine > > > Carboxy There are several types of DNA mutations: 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. Commented [NB1]: Original DNA coding sequence: the code after the introns have been spliced out (cut from the sequence) Transcribe the DNA code into the template strand, mRNA, define the anti0codon on the tRNA and find the amino acid that should be added. Original DNA coding sequence: ATG ACC TTG GCG ACG TAG Template strand TAC TGG AAC CGC TGC ATC mRNA transcript: AUG ACC UUG GCG ACG UAG amino acids: Met Thr Leu Ala Thr stop Highlight the part of the original DNA sequence that has been mutated in the last few sequences. Transcribe the DNA code into the template strand, mRNA, define the anti0codon on the tRNA and find the amino acid that should be added. Highlight the type of mutation and the effect on the new protein sequence. Original DNA coding sequence: Mutated DNA sequence #1: Template strand mRNA transcript: amino acids: Type of mutation (Circle one.) How did the mutation affect the amino acid sequence (protein)? (Circle one.) ATG ACC ATG ATC TAC TAG AAC CGC TGC ATC AUG AUC UUG GCG ACG UAG He Leu Ala Thr Met Point ð TTG 1 amino acid changed ACG TAG TTG GCG ACG TAG Frameshift ð Substitution No change GCG Premature stop signal No stop signal Stop Insertion 1 amino acid added/ deleted or Deletion All the amino acids changed after the point of mutation Explain the resulting protein. The mutationof ACC made the resulting amino acid be He when instead the amino acid prior to the mutation would have been Thr. Original DNA coding sequence: Mutated DNA sequence #2: Template strand mRNA transcript: amino acids: Type of mutation (Circle one.) How did the mutation affect the amino acid sequence (protein)? (Circle one.) ATG ACC ATG ACG TTG TTG GCG ACG TAG GCG ACG TAG TAC TGC AAC CGC TGC ATC AUG ACG UUG GCG ACG UAG Met Thr Leu Ala Thr Point ð No change Frameshift ð Substitution 1 amino acid changed Premature stop signal No stop signal Stop Insertion 1 amino acid added/ deleted or Deletion All the amino acids changed after the point of mutation Explain the resulting protein. The resulting amino acid for ACC stayed the same even after the mutation Original DNA coding sequence: Mutated DNA sequence #3: ATG ATG mRNA transcript: Met Point ð GCG TGG ACC GCT ACC UGG CGA Thr Trp Arg 1 amino acid changed Premature stop signal TAG CGT AGT GCA TCA CGU AGU Arg Frameshift ð Substitution No change ACG CGA TGG AUG amino acids: TTG ACC TAC Template strand Type of mutation (Circle one.) How did the mutation affect the amino acid sequence (protein)? (Circle one.) ACC No stop signal Ser Insertion 1 amino acid added/ deleted or Deletion All the amino acids changed after the point of mutation Explain the resulting protein. The deletion of T in TTG made all of the amino acids after the point of the mutation change. Original DNA coding sequence: Mutated DNA sequence #4: Template strand mRNA transcript: amino acids: ATG ACC TTG GCG ACG TAG ATG ACC TTG GCG CAC GTA GAG TAC AUG Met Type of mutation Point ð (Circle one.) How did the mutation affect the amino acid No change sequence (protein)? (Circle one.) TGG AAC CGC GTG CAT ACC UUG GCG CAC GUA Thr Leu Ala His Val Frameshift ð Substitution 1 amino acid changed Premature stop signal No stop signal CTC GAG Insertion 1 amino acid added/ deleted Glu or Deletion All the amino acids changed after the point of mutation Explain the resulting protein. After C was inserted in front of ACG everything shifted over causing the resulting amino acids to change. Original DNA coding sequence: Mutated DNA sequence #5: Template strand mRNA transcript: amino acids: Type of mutation (Circle one.) How did the mutation affect the amino acid sequence (protein)? (Circle one.) ATG ACC ATG ACC TTG TTG GCG ACG TAG GCG ACG CAG TAC TGG AAC CGC TGC GTC AUG ACC UUG GCG ACG CAG Met Thr Leu Ala Thr Point ð No change Frameshift ð Substitution 1 amino acid changed Premature stop signal No stop signal Gln Insertion 1 amino acid added/ deleted or Deletion All the amino acids changed after the point of mutation Explain the resulting protein. The C was substituted for T in TAG which caused TAG end amino acid to change. CONCLUSIONS 1. Which type of mutation (s) is responsible for new variations (alleles) of a trait? Frameshift mutations can be responsiable for new alleles because they shift the entire DNA sequence. 2. Which type of mutation(s) results in abnormal amino acid sequence? Most substitutions, insertions, and deletions cause an abnormal amino acid sequence. An abnormal amino acid sequence does not occur only when the change happens to be a letter that has the same amino acid as the original. 3. Which type of mutation stops the translation of the mRNA? When the mutation causes the code to turn into eitherUAG, UAA or UGA there will be a stop. 4. A geneticist found that a particular mutation had no effect on the protein coded by a gene. What do you think is the most likely type of mutation in this gene? Why? The mutation was most likely a substitution because there is a higher chance of the mutation not changing the end amino acid if the letters are still in the same section. 5. Examine your genetic code chart. Name one amino acid that has more than one codon. Name an amino acid that has only one codon. An amino acid that has multiple codons is Thr. An amino acid that has only one codon is Trp (the codon is AGG). 6. Given the following three mRNA sequences, determine which two code for the same protein. Circle them. mRNA #1 mRNA #2 mRNA #3 mRNA Transcript AGU UUA GCA ACG AGA UCA UCG CUA GCG ACC AGU UCA AGC CUC GCC ACU CGU AGU Translate Ser Leu Ala Thr Arg Ser Ser Leu Ala Thr Ser Ser Ser Leu Ala Thr Arg Ser 7. How can you identify the mRNA transcript from a code on DNA? Since A and T are pairs and C and G are pairs you can automatically know that when the DNA code has an A the mRNA code is a T and when the DNA code has a C the mRNA code is a G and vis versa. 8. What are the triplets called that code for each amino acid? What is the triplets on tRNA called that match the amino acids to the correct mRNA code? The triplets are called triplet codes. The triplets on tRNA that match amino acids to mRNA are called the gentic code. 9. What does the codon CCT code for? CCT codes for Pro 10. What is the codon(s) for Gln? The codons are CAA qand CAG