Chapter 13 Practice Problems

Mutations Place the correct word into each sentence to describe the different types and causes of mutations.

A gene mutation is a change in the sequence of bases of DNA. These changes in bases can affect protein production, protein activity, or have no effect on protein production or activity at all. Germline mutations are those that occur in sex cells and can be passed on to future generations. Somatic mutations occur in body cells of an individual. Some mutations are spontaneous and happen for no apparent reason. Other mutations are called induced mutations and are the result of exposure to toxins or radiation.

Mutations and cancer Complete each statement to explain how mutations may cause cancer.

Although somatic mutations are not passed on to future generations, they can lead to the development of cancer. Many mutagens, which cause induced mutations, are carcinogens, or cancer-causing mutagens. The organic chemicals in tobacco smoke as well as several forms of radiation are examples of such mutagens. The development of cancer involves the accumulation of mutations; mutation of proto-oncogenes leads to unregulated stimulation of cell division. When tumor suppressor genes are inactive and oncogenes are active, cells divide uncontrollably. Tumor suppressor genes and proto-oncogenes often code for transcription factors or proteins that control transcription factors. Thus, when mutated, normal control of transcription, and thus gene expression, is disrupted.

In a frameshift mutation caused by a deletion, all of the amino acids before the shift are changed.

False

Point mutations Place the correct word into each sentence for more information on the different types of mutations.

Point mutations include changes in one base of a segment of DNA. A point mutation can result in no change in protein synthesis, or in a different protein being made, like in the example of hemoglobin above. Sometimes a point mutation can lead to an improper stop codon, resulting in the termination of synthesis before the protein is completely made.

The addition of a single nucleotide to the DNA sequence causes a frameshift mutation.

True

The nucleic acid sequence in mRNA is determined by

nucleotide sequence in DNA.

A nucleotide deletion in DNA replication

results in a change in the codons in mRNA from the point of the deletion onward, changing the sequence of amino acids inserted into the protein.

If a frameshift mutation causes a stop codon to be inserted into the DNA sequence,

the resulting protein will be shortened and often nonfunctional.

Mutations 2 Use the images below to complete the discussion on mutations and their effects. Figure 1 shows no mutation. Responses can be used more than once.

Figure 1 depicts a point mutation, in which a single DNA nucleotide has been changed. These changes have effects on a single codon within the sequence, and therefore a single amino acid. Figure 2 is an example of a frameshift mutation, in which a single DNA nucleotide has been inserted. These changes have effects on all following codons within the sequence, and therefore many amino acids. Figure 3 depicts a frameshift mutation, in which a single DNA nucleotide has been deleted. These changes have effects on all following codons within the sequence, and therefore many amino acids.

Genetic mutations Use your knowledge of genetic mutations to complete the following statements. Responses can be used more than once.

A genetic mutation is a change in the sequence of bases in DNA. This can have negative effects on the organism because a change in DNA bases can change the resulting protein. Mutations that occur in body cells are called somatic mutations, and those that oocur in sex cells are called germline mutations. There are several different types of mutations. Those that involve a change in a single base are called point mutations. Those that insert or delete one or more bases are called frameshift mutations. An example of a disorder caused by a point mutation is sickle-cell disease. An example of a disorder caused by a frameshift mutation is cystic fibrosis.