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Ch. 16 - How Genes Work
Freeman - Biological Science 7th Edition
Freeman7th EditionBiological ScienceISBN: 9783584863285Not the one you use?Change textbook
All textbooksFreeman 7th EditionCh. 16 - How Genes WorkProblem 8
Chapter 16, Problem 8

Explain what's wrong with this statement: All point mutations change the genotype and the phenotype.

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1
Identify the types of point mutations: Point mutations include substitutions, insertions, or deletions of a single nucleotide in DNA.
Understand genotype and phenotype: Genotype refers to the genetic makeup of an organism, while phenotype refers to the observable characteristics or traits of an organism.
Recognize that not all point mutations alter the phenotype: Some point mutations are silent mutations, where the change in the nucleotide does not affect the amino acid sequence due to the redundancy in the genetic code.
Examine the effect on genotype: All point mutations do change the genotype since they alter the DNA sequence, even if the change does not affect the phenotype.
Conclude the accuracy of the statement: The statement is partially incorrect because while all point mutations change the genotype, not all change the phenotype.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Point Mutations

Point mutations are changes in a single nucleotide base pair in the DNA sequence. They can be classified into three types: silent, missense, and nonsense mutations. While some point mutations can lead to changes in the protein produced, others may not affect the protein at all, particularly if they occur in non-coding regions or result in the same amino acid due to the redundancy of the genetic code.
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Mutations

Genotype vs. Phenotype

The genotype refers to the genetic makeup of an organism, while the phenotype is the observable physical or biochemical characteristics resulting from the genotype and its interaction with the environment. Not all changes in genotype lead to observable changes in phenotype, as some mutations may be neutral or occur in regions of DNA that do not influence traits.
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Silent Mutations

Silent mutations are a specific type of point mutation that do not result in a change in the amino acid sequence of a protein. This occurs because of the redundancy in the genetic code, where multiple codons can code for the same amino acid. As a result, silent mutations can alter the genotype without affecting the phenotype, demonstrating that not all point mutations lead to observable changes.
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Related Practice
Textbook Question

Which of the following describes mutations? Select True or False for each statement.

T/F Point mutations can occur in any DNA sequence.

T/F Frameshift mutations can occur in any DNA sequence.

T/F Neutral mutations depend on the degeneracy of the genetic code.

T/F Deleterious mutations occur only in protein-coding sequences of DNA.

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Textbook Question
Which of the following describes mutations? Select True or False for each statement.T/F Point mutations can occur in any DNA sequence.T/F Frameshift mutations can occur in any DNA sequence.T/F Neutral mutations depend on the degeneracy of the genetic code.T/F Deleterious mutations occur only in protein-coding sequences of DNA.
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Textbook Question
In a particular bacterial species, temperature-sensitive conditional mutations cause expression of a wild-type phenotype at one growth temperature and a mutant phenotype at another—typically higher—temperature. Imagine that when a bacterial cell carrying such a mutation is shifted from low to high growth temperatures, RNA polymerases in the process of elongation complete transcription normally, but no new transcripts can be started. The mutation in this strain most likely affects:a. the terminator sequenceb. the start codonc. sigmad. one of the polypeptides of the core RNA polymerase
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Textbook Question
Explain what's wrong with this statement: All point mutations change the genotype and the phenotype.
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Textbook Question
Draw a hypothetical metabolic pathway in Neurospora crassa composed of five substrates, five enzymes, and a product called nirvana. Number the substrates 1–5, and label the enzymes A–E, in order. (For instance, enzyme A catalyzes the reaction between substrates 1 and 2.) (a) Suppose a mutation made the gene for enzyme C nonfunctional. What molecule would accumulate in the affected cells?
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Textbook Question
Draw a hypothetical metabolic pathway in Neurospora crassa composed of five substrates, five enzymes, and a product called nirvana. Number the substrates 1–5, and label the enzymes A–E, in order. (For instance, enzyme A catalyzes the reaction between substrates 1 and 2.) (b) Suppose a mutant strain can survive if substrate 5 is added to the growth medium, but it cannot grow if substrates 1, 2, 3, or 4 are added. Which enzyme in the pathway is affected in this mutant?
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