IB Biology D1.3 study notes: gene and chromosome mutations, mutagens, the sickle-cell example, somatic versus germline mutations, and CRISPR gene editing.
Here are 10 practice questions with full answers and explanations.
Structural changes to genes at the molecular level.
Changes in protein folding.
Changes in cell structure.
Changes in environmental conditions.
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WhyGene mutations are structural changes to the DNA base sequence of a gene at the molecular level.
2Multiple choice
Which of the following is a type of gene mutation?
Substitution.
Transcription.
Translation.
Replication.
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WhySubstitution, where one base replaces another, is a common type of gene mutation.
3Multiple choice
What are single-nucleotide polymorphisms (SNPs) the result of?
Base substitution mutations.
Insertion mutations.
Deletion mutations.
Frameshift mutations.
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WhySNPs arise from base substitution mutations that change a single nucleotide in the DNA sequence.
4Multiple choice
What is a likely consequence of insertions and deletions?
Polypeptides ceasing to function.
Increased protein synthesis.
Enhanced DNA repair.
Stable gene expression.
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WhyInsertions and deletions cause frameshifts that can render the resulting polypeptide non-functional.
5Multiple choice
What is a frameshift change?
A shift in the reading frame due to insertions or deletions.
A change in a single nucleotide.
A mutation in RNA.
A change in protein folding.
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WhyA frameshift shifts the reading frame of codons downstream of an insertion or deletion.
6Multiple choice
Which of the following factors can cause gene mutations (changes in the DNA sequence)?
I. Errors that occur during DNA replication, such as incorrect base pairing or slippage
II. Exposure to environmental mutagens like certain chemicals (e.g., intercalating agents, base analogs) and various types of radiation (e.g., UV light, X-rays)
III. Spontaneous chemical changes to DNA bases that occur naturally within the cell, such as depurination or deamination
IV. The normal process of protein synthesis within ribosomes
I and II only
I, II, and III only
II and IV only
All I, II, III and IV
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WhyMutations can be caused by mutagens, radiation, and replication errors, so all listed factors apply.
7Multiple choice
Where can mutations occur in a genome?
Anywhere in the base sequences.
Only in coding regions.
Only in non-coding regions.
Only at telomeres.
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WhyMutations can occur anywhere in the base sequences of a genome, in coding or non-coding regions.
8Multiple choice
What is a characteristic of mutations?
They are random.
They are always beneficial.
They are always harmful.
They are predictable.
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WhyMutations occur randomly, without regard to whether they benefit the organism.
9Multiple choice
Which of the following statements accurately describe the consequence of mutations occurring in germ cells (cells that give rise to gametes)?
I. The mutation can be inherited by the offspring of the affected individual
II. If inherited, the mutation will be present in every cell of the resulting offspring
IV. These mutations are a source of genetic variation upon which natural selection can act, contributing to evolution
III. They directly cause diseases or abnormalities in the individual in whom the mutation originates (the parent)
I and II only
I, II, and III only
II and IV only
I, II, and IV only
All I, II, III and IV
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WhyGerm-cell mutations can be passed to offspring, affect all their cells, and contribute to evolution.
10Multiple choice
Which of the following statements accurately describe the consequence of mutations occurring in somatic cells?
I. The mutation is generally not passed on to the offspring of the affected individual
II. They can lead to various diseases, such as cancer, if they affect genes that regulate cell growth and division
III. They can contribute to the aging process and the accumulation of cellular damage over an individual's lifetime
IV. They are a primary source of new genetic variation for the evolution of a species
I, II, and III only
I and II only
II and III only
All I, II, III and IV
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WhySomatic mutations affect only the individual, are not inherited, and can lead to cancer.
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