TOPIC 12 DAY 4 TYPES OF MUTATIONS

A substitution mutation occurs in a DNA sequence, as represented above. The table above shows the mRNA codons for some amino acids.

Based on this information, what is the expected effect of the mutation?

• The polypeptide will have fewer amino acids.

• The polypeptide will contain a different amino acid.

• The polypeptide will have the same amino acids.

• The polypeptide will contain an additional amino acid.

Answer explanation

A substitution mutation changes one nucleotide, potentially altering a codon. This can lead to a different amino acid being incorporated into the polypeptide, making 'The polypeptide will contain a different amino acid' the correct choice.

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All six codons listed above code for the same amino acid during protein synthesis.

Which of the following statements describes an advantage of having multiple codons for the same amino acid?

• The length of the protein chain will be reduced.

• The effect of mutations in the DNA could be reduced.

• The ribosome will more quickly read the order of the bases during translation.

• The cell could use the bases that are most available in the nucleus to assemble DNA.

Answer explanation

Having multiple codons for the same amino acid reduces the impact of mutations, as a change in one codon may still result in the same amino acid being produced, thus maintaining protein function.

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How is a point mutation different from a frameshift mutation?

• A point mutation always results in a frameshift mutation.

• A point mutation only results in a change in a single nucleotide base, while a frameshift mutation can result in a change in multiple nucleotide bases.

• A point mutation is a physical change, and a frameshift mutation is a chemical change.

• A point mutation is always harmful, and a frameshift mutation is never harmful.

Answer explanation

A point mutation changes only one nucleotide base, while a frameshift mutation alters the reading frame, potentially affecting multiple bases. This distinction is crucial in understanding genetic mutations.

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SC.912.L.16.4

A normal strand of DNA is shown in the image, followed by the same strand of DNA after a mutation has occurred.

Which mutations have taken place?

• point and inversion mutations

• deletion and frameshift mutations

• inversion and deletion mutations

• point and frameshift mutations

Answer explanation

The mutation shows a segment of DNA that has lost nucleotides (deletion) and has altered the reading frame, causing a frameshift. This combination confirms the presence of deletion and frameshift mutations.

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SC.912.L.16.4

What type of mutation occurs when a nucleotide base is replaced by another nucleotide base without changing the resulting amino acid causing no recognizable effects upon the phenotype of the organism?

• frameshift mutation

• silent mutation

• nonsense mutation

• missense mutation

Answer explanation

A silent mutation occurs when a nucleotide is replaced but does not change the amino acid sequence, resulting in no observable effect on the organism's phenotype. This distinguishes it from other mutation types.

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SC.912.L.16.4

Doctors are studying a patient with a form of leukemia. When they examine the patient’s chromosomes, they discover that a section of Chromosome 9 has broken off and attached to Chromosome 22. This change causes two genes that are normally on different chromosomes to join together, affecting how cells divide.

Which type of chromosomal mutation is best described in this situation?

• Deletion

• Translocation

• Inversion

• Duplication

Answer explanation

The situation describes a segment of Chromosome 9 breaking off and attaching to Chromosome 22, which is a classic example of translocation. This type of mutation involves the rearrangement of genetic material between non-homologous chromosomes.

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