Gene mutations and what they do to a protein
Grade 9 Science Worksheet
Circle the best answer.
Read this first
Original mRNA (model, not to scale), 5′ to 3′, cut into codons
AUG GGA CUU AAG UAA. Changed mRNA (model), 5′ to 3′, cut into codons: AUG GGA CCU AAG UAA. The marked letter is base 8 of the changed mRNA. Table excerpt of the standard genetic code: AUG, methionine; GGA, glycine; CUU, leucine; AAG, lysine; UAA, stop; CCU, proline.
Ari translates both model mRNAs. How do the two chains compare?
- The chains match, because one letter is too small to matter
- Both start the same, but the amino acids after the change are different
- The changed chain stops after glycine, because CCU ends the chain
- Both have four amino acids; leucine is replaced by proline
Original mRNA (model, not to scale), 5′ to 3′, cut into codons
AUG UCU GCU GGA UAA. Changed mRNA (model), 5′ to 3′, cut into codons: AUG UCA GCU GGA UAA. The marked letter is base 6 of the changed mRNA. Table excerpt of the standard genetic code: AUG, methionine; UCU, serine; GCU, alanine; GGA, glycine; UAA, stop; UCA, serine.
Bo translates both model mRNAs. How many amino acids differ between the chains, and what kind of change is it?
- Two amino acids are lost; the change is nonsense
- No amino acid differs, but the protein is harmed anyway
- No amino acid differs; the change is silent
- One amino acid differs; the change is missense
Original mRNA (model, not to scale), 5′ to 3′, cut into codons
AUG GAC UUG CAG AAA UAA. Changed mRNA (model), 5′ to 3′, cut into codons: AUG GAC UUG UAG AAA UAA. The marked letter is base 10 of the changed mRNA. Table excerpt of the standard genetic code: AUG, methionine; GAC, aspartic acid; UUG, leucine; CAG, glutamine; AAA, lysine; UAA, stop; UAG, stop.
Esme translates both model mRNAs. The original chain has five amino acids. How many are in the changed chain?
- 3 amino acids: the chain ends at UAG, before lysine
- 4 amino acids: UAG adds one last amino acid, then the chain ends
- 5 amino acids: the message keeps the same length
- 2 amino acids: the chain ends one codon early
Original mRNA (model, not to scale), 5′ to 3′, not yet cut
AUGGAUCUGAAACCUGGC. Copy (model), 5′ to 3′, not yet cut: AUGGAUCCUGAAACCUGGC. The marked letter is base 7 of the copy. Read six codons of each strand, starting at AUG. Table excerpt of the standard genetic code: AUG, methionine; GAU, aspartic acid; CUG, leucine; AAA, lysine; CCU, proline; GGC, glycine; GAA, glutamic acid; ACC, threonine; UGG, tryptophan.
Jun compares a model mRNA with a copy that has one extra base (marked). Both are read in threes from AUG. How many of the six amino acids differ?
- 4: the amino acids from the insertion onward
- 5: the amino acids after methionine
- 1: just the amino acid at the insertion
- 0: the extra base is not read as part of a codon
Original mRNA (model, not to scale), 5′ to 3′, not yet cut
AUGCCUGAUAAAUUUGGA. Copy (model), 5′ to 3′, not yet cut: AUGCCUAUAAAUUUGGA. The marked letter is base 7 of the original mRNA. Read five codons of each strand, starting at AUG. Table excerpt of the standard genetic code: AUG, methionine; CCU, proline; GAU, aspartic acid; AAA, lysine; UUU, phenylalanine; GGA, glycine; AUA, isoleucine; AAU, asparagine; UUG, leucine.
Kira’s copy of a model mRNA lacks the marked base. Five codons of the copy are read. How many of its five amino acids differ from the original’s first five?
- 2: the amino acids on each side of the deletion
- 1: just the amino acid at the deletion
- 3: the amino acids from the deletion onward
- 5: the first five amino acids
Original mRNA (model, not to scale), 5′ to 3′, not yet cut
AUGGGAGACCACAACUUC. Copy X (model), 5′ to 3′, not yet cut: AUGCGGAGACCACAACUUC. Copy Y (model), 5′ to 3′, not yet cut: AUGGGAGACCACAACCUUC. The marked letter is base 4 of copy X and base 16 of copy Y. Read six codons of each strand, starting at AUG. Table excerpt of the standard genetic code: AUG, methionine; GGA, glycine; GAC, aspartic acid; CAC, histidine; AAC, asparagine; UUC, phenylalanine; CGG, arginine; AGA, arginine; CCA, proline; CAA, glutamine; CUU, leucine.
Luz compares two copies of a model mRNA, each with one extra base (marked). Which copy changes more amino acids, and why?
- X: more codons come after it and are read in the shifted frame
- Same number: each copy has one extra base, so one amino acid changes
- Neither: an extra base is not read, so the chains are unchanged
- Y: its extra base is nearer the end, so more is lost
Original mRNA (model, not to scale), 5′ to 3′, cut into codons
AUG UGG CAG AAG UAA. Copy (model), 5′ to 3′, not yet cut: AUGUGGCAGACGAAGUAA. The marked letters are bases 9 to 11 of the copy. Table excerpt of the standard genetic code: AUG, methionine; UGG, tryptophan; CAG, glutamine; AAG, lysine; UAA, stop; ACG, threonine.
Milo compares a model mRNA with a copy that has three extra bases (marked). How do the two chains compare?
- 4 amino acids: just the single amino acid at the insertion site changes
- 5 amino acids: threonine is new and the others keep their order
- 7 amino acids: each extra base adds one amino acid
- 5 amino acids: the ones after the insertion are different
Original mRNA (model, not to scale), 5′ to 3′, cut into codons
AUG GAU CUG AAA GGC UAA. Copy (model), 5′ to 3′, not yet cut: AUGGAGAAAGGCUAA. The marked letters are bases 6 to 8 of the original mRNA. Table excerpt of the standard genetic code: AUG, methionine; GAU, aspartic acid; CUG, leucine; AAA, lysine; GGC, glycine; UAA, stop; GAG, glutamic acid.
Noah compares a model mRNA with a copy that lacks three bases (marked in the original). How do the two chains compare?
- 5 amino acids: just the amino acid at the deletion changes
- 4 amino acids: the ones after the deletion are different
- 4 amino acids: two are replaced by one, and lysine and glycine stay
- 2 amino acids: three bases shorten the chain by three
Change card (model data)
change what happened to the gene P 6 bases added Q 1 base added R 2 bases removed S 4 bases removed Pia reads a card of four model changes to one gene. Which change keeps the reading frame of the codons after it?
- Q: one base is too few to move the frame
- No row: any added or removed bases shift the frame
- P: 6 bases make two whole codons
- S: 4 bases removed leaves whole codons behind
Model plants (model data)
plant change to the pigment gene enzyme flowers A none five amino acids purple B silent substitution same five amino acids purple C stop codon at codon 3 two amino acids white Zee reads cards for three model plants. Which statement do the cards support?
- Plant B has a mutation but the same enzyme; only plant C lost the pigment
- Plant B makes a different enzyme, since its gene has a changed letter
- Plant C makes a longer enzyme, since a stop codon adds amino acids
- Plants B and C both have harmed enzymes, because both have mutations