3) Assume the RNA sequence below represents part of the coding sequence of an mR

Question

3) Assume the RNA sequence below represents part of the coding sequence of an mRNA. The normal reading frame is such that the first three bases are in-frame. The arrow indicates the guanine at which (or to the left of which) the changes occur. For each change, give me the new amino acid sequence of this region of the protein and indicate the nature of the mutation both at the DNA level and the protein level. Note that the ellipses indicate that translation begins and ends outside this sequence. (12 pts) 5'...CCUGGAAAUCAGUAC...3' Amino acid sequence DNA level Protein level a) G changes to U b) G changes to A c) G is deleted d) U is inserted (to left of G) 3b) The mutations in question 34 could have been caused by mutagenic chemicals. For each of the mutagens below, indicate which of the mutations above it would be able to cause. Each mutagen may have 0-4 correct answers. You may use each mutation once, more than once, or not at all. (6 pts) Bromouracil Dimethyl sulfate Ethidium bromide

Explanation / Answer

3.

Given mRNA sequence: CCUGGAAAUCAGUAC

Amino acid sequence of given mRNA: Leu-Gly-Asn-Gln-Tyr

DNA sequence

Amino acid

DNA level

Protein level

G changes to U

CCUUGAAAUCAGUAC

Leu-Stop-Asn-Gln-Tyr

Traversion (Replaces purine with a pyrimidine)

Polypeptide chain will terminate at stop codon

G changes to A

CCUAGAAAUCAGUAC

Leu-Arg-Asn-Gln-Tyr

Transition

(Replaces purine with a purine)

Glycine amino acid is replaced with Arginine after leucine

G is deleted

CCUGAAAUCAGUAC

Leu-Glu-Ile-Ser

Deletion (Removal of purine or pyrimidine)

The amino acid sequence is altered after Leucine

U is inserted (left of G)

CCUUGGAAAUCAGUAC

Leu-Trp-Lys-Ser-Val

Insertion (Addition of purine or pyrimidine)

The amino acid sequence is altered after Leucine

3b.

Bromouracil- Point mutation ( Alters base pairing in DNA)

Dimethyl sulfate- Induced mutation by alkylation (Adds methyl group to purine or pyrimidine)

Ethium bromide- Induced mutation by intercalating agent ( Intercalates between the nucleotides and deforms the structure of DNA)

DNA sequence

Amino acid

DNA level

Protein level

G changes to U

CCUUGAAAUCAGUAC

Leu-Stop-Asn-Gln-Tyr

Traversion (Replaces purine with a pyrimidine)

Polypeptide chain will terminate at stop codon

G changes to A

CCUAGAAAUCAGUAC

Leu-Arg-Asn-Gln-Tyr

Transition

(Replaces purine with a purine)

Glycine amino acid is replaced with Arginine after leucine

G is deleted

CCUGAAAUCAGUAC

Leu-Glu-Ile-Ser

Deletion (Removal of purine or pyrimidine)

The amino acid sequence is altered after Leucine

U is inserted (left of G)

CCUUGGAAAUCAGUAC

Leu-Trp-Lys-Ser-Val

Insertion (Addition of purine or pyrimidine)

The amino acid sequence is altered after Leucine

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