Gene mutations and what they do to a protein
Grade 9 Science Worksheet - Building Confidence
Circle the best answer.
Read this first
Original mRNA (model, not to scale), 5′ to 3′, cut into codons
AUG GCU UUC UAA. Changed mRNA (model), 5′ to 3′, cut into codons: AUG GCU GGA UUC UAA. The marked letters are bases 7 to 9 of the changed mRNA.
Ari compares two model mRNAs. The marked letters are only in the changed mRNA. What kind of change is it, and what happens to the later codons?
- Insertion of three bases; the later codons keep their frame
- Deletion of three bases; the later codons keep their frame
- Substitution of three bases; the later codons keep their frame
- Insertion of three bases; the later codons shift their frame
Original mRNA (model, not to scale), 5′ to 3′, not yet cut
AUGGAUCUGAAAUAA. Changed mRNA (model), 5′ to 3′, not yet cut: AUGGAUGCUGAAAUAA. The marked letter is base 7 of the changed mRNA.
Bo compares two model mRNAs. The marked letter is only in the changed mRNA. What kind of change is it, and what happens to the later codons?
- Substitution of one base; the later codons keep their frame
- Insertion of one base; just the next amino acid changes
- Deletion of one base; the later codons shift
- Insertion of one base; the later codons shift
Original mRNA (model, not to scale), 5′ to 3′, cut into codons
AUG GAU UUC UAA. Changed mRNA (model), 5′ to 3′, cut into codons: AUG GAA UUC UAA. The marked letter is base 6 of the changed mRNA. Table excerpt of the standard genetic code: AUG, methionine; GAU, aspartic acid; UUC, phenylalanine; UAA, stop; GAA, glutamic acid.
Kira compares two model mRNAs that differ at the marked letter. Using the table, which kind of change is it?
- Missense: aspartic acid is replaced by glutamic acid
- Nonsense: the new codon is a stop codon
- Frameshift: the later codons are read in a new frame
- Silent: one changed letter is too small to change the amino acid
Original mRNA (model, not to scale), 5′ to 3′, cut into codons
AUG CAG GGA UAA. Changed mRNA (model), 5′ to 3′, cut into codons: AUG UAG GGA UAA. The marked letter is base 4 of the changed mRNA. Table excerpt of the standard genetic code: AUG, methionine; CAG, glutamine; GGA, glycine; UAA, stop; UAG, stop.
Luz compares two model mRNAs that differ at the marked letter. Using the table, which kind of change is it?
- Frameshift: the later codons are read in a new frame
- Missense: the new codon adds a different amino acid
- Silent: the new codon still codes for glutamine
- Nonsense: the new codon is a stop codon
Original mRNA (model, not to scale), 5′ to 3′, cut into codons
AUG CCU AAA UAA. Changed mRNA (model), 5′ to 3′, cut into codons: AUG CCC AAA UAA. The marked letter is base 6 of the changed mRNA. Table excerpt of the standard genetic code: AUG, methionine; CCU, proline; AAA, lysine; UAA, stop; CCC, proline.
Milo translates both model mRNAs with the table. How do the two chains compare?
- The changed chain is one amino acid shorter
- The chains match: CCU and CCC both code for proline
- The chains differ: the second amino acid is new, since a letter changed
- The changed chain is damaged, since a mutation is harmful
Original mRNA (model, not to scale), 5′ to 3′, cut into codons
AUG AAG GAC UAA. Changed mRNA (model), 5′ to 3′, cut into codons: AUG UAG GAC UAA. The marked letter is base 4 of the changed mRNA. Table excerpt of the standard genetic code: AUG, methionine; AAG, lysine; GAC, aspartic acid; UAA, stop; UAG, stop.
Noah translates the changed model mRNA with the table. How many amino acids are in its chain?
- 0 amino acids: the chain cannot begin
- 1 amino acid: methionine, then UAG ends the chain
- 2 amino acids: methionine, then a new one for UAG
- 3 amino acids: the message has the same length
Original mRNA (model, not to scale), 5′ to 3′, cut into codons
AUG GAU AAA CCU UAA. Changed mRNA (model), 5′ to 3′, cut into codons: AUG GAU CCU UAA. The marked letters are bases 7 to 9 of the original mRNA. Table excerpt of the standard genetic code: AUG, methionine; GAU, aspartic acid; AAA, lysine; CCU, proline; UAA, stop.
Pia translates both model mRNAs with the table. The marked letters are only in the original. How do the two chains compare?
- The changed chain is one amino acid shorter: lysine is missing
- The chains match: a deletion takes nothing from the chain
- The changed chain has the same length: lysine becomes proline
- The amino acids after the deletion are different, since the frame shifted
Use this
Cause card (model data), 3 rows. Columns: step, what happened. 1, A cell copied its DNA, and DNA polymerase added a wrong base. 2, Proofreading and repair did not fix the wrong base. 3, The next copy kept the wrong base.
Ren reads a cause card about a change in a gene. Which cause does the card show?
- Proofreading adding a wrong base to the strand
- A change the cell made because it needed it
- A copying error that proofreading and repair did not fix
- UV light joining two thymines side by side
Cause card (model data)
step what happened 1 Ultraviolet (UV) light reaches the DNA in a cell 2 Two thymines side by side join into a thymine dimer 3 Repair enzymes cut out the damaged piece and fill it in Tala reads a cause card about UV light. What does UV light do to the DNA, according to the card?
- It joins two thymines side by side into a thymine dimer
- It copies a gene a second time
- It makes DNA polymerase add a wrong base
- It changes the amino acids in a finished protein
Two cause cards (model data)
cause what the cell can do a copying error Proofreading and repair fix most mistakes UV light Repair enzymes can cut out the damaged piece Zee reads two cause cards, one on copying errors and one on UV light. Which statement fits both cards?
- A change left in the DNA is harmful to the cell that carries it
- The cell makes each change on purpose to help itself
- Repair undoes each change, so a mutation cannot be left in DNA
- Cells repair most of these changes, and a change left in the DNA is a mutation