Gene mutations and what they do to a protein
Grade 9 Science Worksheet - Challenge Me
Circle the best answer.
Read this first
Use this
Lactase card (facts from NIH MedlinePlus Genetics, simplified), 4 rows. Columns: item, what the card says. LCT gene, Gives instructions for making lactase, an enzyme that digests lactose, a sugar in milk. Control region, A short stretch of DNA near LCT that helps control how active the LCT gene is. Most humans, Make less lactase as they get older, because the LCT gene becomes less active after infancy. A single-letter change in the control region, Keeps the LCT gene active, so lactase is still made in adulthood.
Ari reads the lactase card. Where is the single-letter change?
- In the lactase protein, because a changed letter changes the protein
- In an LCT codon, where it swaps one amino acid in lactase
- In the start codon of LCT, so lactase begins at a new place
- In a control region near LCT, not in a codon of the lactase protein
Esme reads the lactase card. Which label fits the single-letter change best?
- None of the three: it is in a control region, not in a codon
- Silent: the codon still codes for the same amino acid in lactase
- Missense: lactase gets a different amino acid
- Nonsense: a new stop codon ends the lactase chain
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Change card (model data), 4 rows. Columns: change, what happens to the protein, effect on the organism. 1: silent substitution, same amino acids, none noticed. 2: stop codon early in an enzyme gene, enzyme ends early, enzyme does not work. 3: missense in a model coat-color gene, one amino acid differs, darker coat. 4: three-base insertion, one amino acid added, none noticed.
Jun reads a card of four model changes. Which conclusion do the rows support?
- Mutations can have no effect, stop a protein, or give a new trait
- Mutations are harmful, but some harm more than others
- A mutation alters the protein, and the size of the alteration differs
- An organism makes a mutation when it needs a new trait
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Codon card (model data), 4 rows. Columns: row, codon before, codon after. 1, UUU, UUA. 2, GAA, GAG. 3, UGG, UGA. 4, AAA, AAU. Table excerpt of the standard genetic code: UUU, phenylalanine; UUA, leucine; GAA, glutamic acid; GAG, glutamic acid; UGG, tryptophan; UGA, stop; AAA, lysine; AAU, asparagine.
Kira reads a card of four model substitutions. Which row is a mutation with no effect on the protein, and why?
- Row 2: GAA and GAG both code for glutamic acid
- Row 3: UGA is another amino acid, so the chain keeps its length
- Row 1: just the third letter changed, so it cannot matter
- No row: a changed letter changes the amino acid
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Model mouse card (model data), 5 rows. Columns: item, what the card says. Gene, a model pigment gene in a model mouse. Change, one base replaced, so one amino acid differs. Enzyme, still works. Coat, darker than before. Growth, the mouse grows as before.
Luz reads a model mouse card. What does the card show about this mutation?
- It appeared because the mouse needed a darker coat
- It must add a stop codon, since a stop codon is what gives a new trait
- It is harmful, because a changed amino acid stops the enzyme
- It gives a new trait, and the mouse grows as before
Notebook (model data)
line what it says 1 A silent substitution changes a base but not the amino acid 2 A missense substitution swaps one amino acid for another 3 A frameshift changes the codons from the change onward 4 Adding three bases always shifts the reading frame Milo reviews a classmate’s notebook on mutations. Exactly one line is wrong. Which line, and why?
- Line 4, because three bases make a whole codon and the frame stays
- Line 2, because a missense change leaves the chain the same
- Line 3, because a frameshift changes just the next amino acid in the chain
- Line 1, because a changed base changes the amino acid
Noah reviews a classmate’s notebook on mutations. Exactly one line is wrong. Which line, and why?
- Line 3, because some mutations have no effect or give a new trait
- Line 4, because UV light works through DNA polymerase
- Line 1, because a stop codon adds amino acids
- Line 2, because a changed letter changes the protein
Pia reviews a classmate’s notebook on mutations. Exactly one line is wrong. Which line, and why?
- Line 1, because repair fixes the errors, so no error is left
- Line 4, because an error counts as a mutation just when it is harmful
- Line 2, because UV light, not DNA polymerase, makes thymine dimers
- Line 3, because deleting three bases shifts the frame
Use this
Deletion card (model data), 3 rows. Columns: item, what the card says. Message, 10 codons, 30 bases. Change P, 1 base deleted from codon 3; 29 bases left. Change Q, 3 bases deleted from codon 3; 27 bases left.
Ren reads a card about two deletions in a model message. Which claim and reason go together?
- P changes more amino acids, because 29 bases is longer than 27 bases
- P and Q change one amino acid each, because each deletes bases from just one codon
- Q changes more amino acids, because three bases shift the frame by a codon
- P changes more amino acids, because it shifts the frame for the codons after it
Nonsense card (model data)
change stop codon appears at amino acids in the chain none (original) codon 12 11 X codon 3 2 Y codon 11 10 Zee reads a card about two nonsense changes to a model enzyme gene. Which claim and reason go together?
- Y is more likely to stop the enzyme working, because it is nearer the end
- X and Y have the same effect, because each changes one letter
- X is more likely to stop the enzyme working, because it removes nine amino acids and Y one
- Y changes the enzyme more, because its stop codon adds amino acids at the end