Genetics Problems

BIO 221 Genetics Practice Problems

Problem Set 1

Use the template gene 3TACAACGGTAAGAACCAT5 for the following questions. Label the 3 and 5 ends.

1. How many amino acids are encoded by this sequence?

2. How many codons are encoded by this sequence?

3. Give the sequence of the fourth nontemplate triplet, with 3 and 5 ends labeled.4. Give the second and third amino acids encoded by the template DNA.5. Give the sequence of the fifth anticodon, with 3 and 5 ends labeled.6. Give one nontemplate DNA sequence associated with the following peptide: Methionine-Isoleucine-Cysteine-Glutamic Acid-ThreonineProblem Set 2

Use the template gene 3ACCCGCAAATTA5 for the following questions. Label the 3 and 5 ends.1. Give the amino acid sequence encoded by the template gene.

2. Give the nontemplate DNA sequence, with 3 and 5 ends labeled.

3. Give the third anticodon sequence, with 3 and 5 ends labeled.

4. Give the second nontemplate DNA triplet, with 3 and 5 ends labeled.5. Give the number of mRNA nucleotides encoded by the template gene.6. Give the number of mRNA codons encoded by the template gene.Problem Set 3

Use the anticodon sequence 5-AAU-3 for the following questions:

1. Give the nontemplate DNA triplet, with 3 and 5 ends labeled.2. Give the encoded amino acid.Use the mRNA codon 3-CAU-5 for the following questions:

3. Give the template DNA triplet, with 3 and 5 ends labeled.4. Give the tRNA anticodon, with 3 and 5 ends labeled.

Problem Set 4

Use the wild type template sequence 3TACAAATTAGGCCAT5 for the following questions:

1. Give the amino acid sequence for this tDNA.

2. Give the mutated DNA sequence if a thymine dimer due to UV radiation was uncorrected.3. Give the amino acid sequence for the mutated tDNA.4. Is the mutation above a frameshift or point? Explain.Problem Set 5

Use the wild type template sequence 3TACAACGGTAAGAACCAT5 for the following questions:

1. Give the amino acid sequence for the wild type (normal) DNA.

2. Diagram and explain the effect of a mutation where G is replaced by A in triplet 4.

3. Diagram and explain the effect of a mutation where G is replaced by A in the 1st position of triplet 3.

4. Diagram and explain the effect of a mutation where A is replaced by T in the 2nd position of triplet 5.

5. Diagram and explain the effect of a deletion of the first two nucleotides of triplet 2.

ANSWERS FOLLOW

ANSWERS

Problem Set 1

1. 6

2. 6

3. 5-TTC-3

4. Leucine-Proline5. 3-AAC-5 6. Answers vary; one sequence: 5-ATGATT/ATCTGT/TGCGAA/GAGACT/ACA/ACC/ACG-3

Problem Set 2

1. Tryptophan-Alanine-Phenylalanine-Asparagine

2. 5-TGGGCGTTTAAT-3

3. 3-AAA-5

4. 5-GCG-3

5. 12

6. 4

Problem Set 31. 5-ATT-3 (recall that the codon is 5( 3)2. Isoleucine

3. 3-ATG-5 (recall that the codon is 5( 3)4. 3-AUG-5

Problem Set 4

1. Methionine-Phenylalanine-Asparagine-Proline-Valine

2. 3-TACAAAAGGCCAT-5

3. Methionine-Phenylalanine-Serine-Glycine

4. Frameshift. With a point mutation, one nucleotide is substituted but the nucleotide number remains the same. The thymine dimer causes a deletion of two nucleotides, shifting the DNA reading frame to the left.

Problem Set 5

1. MethionineLeucineProlinePhenylalanineLeucineValine

2. WT: 3-AAG(5-UUC( PHE / MT: 3-AAA( 5-UUU ( PHE = Silent, Point

3. WT: 3-GGT (5-CCA ( PRO / MT: 3-AGT( 5-UCA( SER = Missense, Point

4. WT: 3-AAC ( 5-UUG( LEU / MT: 3-ATC ( 5-UAG( STOP = Nonsense, Point

5. WT: 3-TAC-AAC-GGT-AAG-AAC-CAT-5 ( MT: 3-TAC- CGG-TAA-GAA-CCA-T5 (

MET-LEU-PRO-PHE-LEU-VAL ( MET-ALA-ILE-LEU-GLY = Frameshift, Missense