Question 1

A chemical or physical agent that causes mutations is called a
A) mutator.
B) tautomer.
C) teratomer.
D) mutagen.
E) collagen.

Accepted Answer

A mutagen is any agent that causes a change in the DNA sequence by inducing mutations. Mutations can be caused by chemical agents called chemical mutagens, physical agents called physical mutagens, or biological agents called biological mutagens.

Question 2

A germline mutation passes from generation to generation because it occurs during the DNA replication before
A) mitosis.
B) meiosis.
C) fertilization.
D) puberty.
E) RNA replication.

Accepted Answer

Germline mutations occur in the reproductive cells and are passed down to offspring through meiosis, as these cells undergo cell division to form gametes. Mutations occurring after fertilization in somatic cells cannot be passed down to future generations. The other options are not directly related to the passing on of mutations.

Question 3

Mutations in the lamin A gene are responsible for very diverse disorders because
A)different tissues have different variants of the gene.
B)lamin A proteins affect how chromatin touches the nuclear membrane.
C)many different results occur.
D)every tissue type has lamin A.
E)they are only active under certain conditions.

Accepted Answer

Lamin A proteins play a crucial role in maintaining the structure of the nuclear envelope and influence how chromatin interacts with the nuclear membrane, affecting gene expression and leading to diverse disorders.

Question 4

The first single-gene disorder for which the mechanism of mutation was understood was
A) cystic fibrosis.
B) Duchenne muscular dystrophy.
C) hemophilia.
D) sickle cell disease.
E) diabetes mellitus.

Accepted Answer

The mechanism of mutation causing sickle cell disease was first understood in 1949, making it the first single-gene disorder for which the mechanism was elucidated.

Question 5

A somatic mutation
A) occurs only in microbes.
B) affects a particular subset of cells.
C) affects all cells of an individual.
D) is expressed only in embryos.
E) affects sleep cycles.

Accepted Answer

Somatic mutations are mutations that occur in somatic cells, which are any cells in the body that are not involved in reproduction. These mutations can affect a particular subset of cells, such as those in a specific tissue or organ, rather than all cells in an individual.

Answer: C 
 However, somatic mutations can also affect all cells of an individual, particularly if they occur early in development or in a stem cell that gives rise to multiple different cell types.

Answer: A, D, E 
 None of these answer choices accurately describe a somatic mutation.

Question 6

A mutation in a collagen gene is likely to affect the phenotype because
A) it is extremely rare.
B) during meiosis, the chromosome that bears the mutation is more likely to enter a gamete than the chromosome that carries the wild type allele.
C) collagen has a very precise three-dimensional structure, so nearly any disruption alters the overall conformation.
D) people who use cosmetics with collagen silence collagen genes.
E) there are many collagen genes.

Accepted Answer

Collagen has a very precise three-dimensional structure, so nearly any disruption alters the overall conformation. Therefore, a mutation in a collagen gene is likely to affect the phenotype.

Question 7

Spontaneous mutation occurs when
A) a DNA base is in a rare tautomeric form as the replication fork arrives, and a mismatched base is inserted.
B) a person smokes cigarettes or is exposed to a teratogen for many years.
C) the sugars and phosphates in the DNA double helix exchange places.
D) thymine temporarily becomes uracil.
E) a replication fork stalls.

Accepted Answer

Spontaneous mutation occurs when a DNA base is in a rare tautomeric form as the replication fork arrives, and a mismatched base is inserted. Tautomeric shift is a temporary change in the structure of a nucleotide base that creates a nonstandard Watson-Crick base pairing. This can result in the insertion of a wrong nucleotide during DNA replication, leading to a mutation.

Question 8

Sanjay and Indira have thalassemia minor.Their young daughters are dizygotic (fraternal)twins.Malonie has thalassemia minor like her parents,but Jewel has the more severe thalassemia major.The more serious case most likely arose because
A) Jewel inherited two wild type alleles from her carrier parents.
B) Jewel inherited a dominant form of the condition.
C) Jewel inherited two recessive mutant alleles in the beta globin gene that cause thalassemia.
D) Jewel also has sickle cell disease.
E) Malonie underwent a deletion in the beta globin gene.

Accepted Answer

Thalassemia major is inherited recessively, meaning that an individual must inherit two copies of the mutated beta globin gene from both parents to develop the more severe form of the disease. Sanjay and Indira both have thalassemia minor, which means they each carry one copy of the mutated gene and one wild-type gene. The chance of their dizygotic twins inheriting two copies of the mutated gene is 25%. Malonie inherited one mutated gene from each parent, resulting in her having thalassemia minor like her parents. However, Jewel inherited two copies of the mutated gene, resulting in her having thalassemia major. Therefore, the most likely explanation for the more severe form of the disease in Jewel is that she inherited two recessive mutant alleles in the beta globin gene that cause thalassemia.

Question 9

The chance that the average gene undergoes a spontaneous mutation is about 1 in
A) 100.
B) 1,000.
C) 10,000.
D) 100,000.
E) 1,000,000.

Accepted Answer

The average gene undergoes a spontaneous mutation at a rate of about 1 in 100,000.

Question 10

___ gene(s)encode chains of the same collagen molecule.
A) One
B) Two
C) Three
D) Four
E) Ten

Accepted Answer

The answer of ___ gene(s)encode chains of the same collagen...

Question 11

The parents-to-be were shocked when an ultrasound scan done in the second trimester of the pregnancy showed a fetus with obviously broken leg bones and ribs.The doctor diagnosed osteogenesis imperfecta.This is caused by a mutation in a gene that encodes
A) beta globin.
B) alpha globin.
C) a clotting factor.
D) myosin.
E) collagen.

Accepted Answer

Osteogenesis imperfecta is a genetic disorder caused by a mutation in the gene that codes for collagen, a protein that helps to provide structure to bones and other connective tissues in the body. The mutation results in weakened bones that are prone to breaking easily, as well as other symptoms such as short stature and hearing loss. The other choices listed (beta globin, alpha globin, a clotting factor, and myosin) are not associated with this disorder.

Question 12

In Ehlers-Danlos syndrome type 1,collagen molecules are
A) too short.
B) missing.
C) too long.
D) too scarce.
E) too abundant.

Accepted Answer

The answer of In Ehlers-Danlos syndrome type 1,collagen molecules are
A)...

Question 13

An example of a beneficial mutation is
A) a mutation in collagen that causes the skin to be extra stretchy.
B) the mutation that causes sickle cell disease.
C) a mutation in the CCR5 gene.
D) a mutation in a cytokine gene that causes an allergy.
E) a mutation that causes a person to be neither right nor left-handed.

Accepted Answer

A mutation in the CCR5 gene can confer resistance to the human immunodeficiency virus (HIV). This mutation is present in some individuals and prevents the virus from entering and infecting certain types of immune cells. This is a beneficial mutation because it confers a survival advantage against a deadly and widespread disease.

Question 14

A man and woman of normal height have a son with achondroplasia.They want to have another child,and wonder what the risk is that he or she will also have this form of dwarfism.The risk is
A) 0 percent.
B) the same as for any other child in the population.
C) 25 percent.
D) 50 percent.
E) 50 percent for a boy and 25 percent for a girl.

Accepted Answer

Achondroplasia is usually caused by a new mutation, and the risk for future children is the same as for any other child in the population unless one parent has the condition.

Question 15

Estimates of spontaneous mutation rates are made using dominant disorders because
A) it takes several generations for the phenotype to change.
B) they do not affect offspring.
C) the mutant phenotype is obvious.
D) they can be identified by DNA sequencing.
E) they are much more common than recessive disorders.

Accepted Answer

Dominant disorders produce an obvious mutant phenotype, which makes it easier to identify and track mutations. This allows for more accurate estimation of spontaneous mutation rates.

Question 16

A mutation is
A) a change in a DNA sequence that affects at least 10 percent of individuals in a population.
B) a change in a DNA sequence present in less than 1 percent of individuals in a population.
C) a change in a DNA sequence that harms health.
D) a type of radiation that can alter the genetic code.
E) a substitution of amino acids for nucleotides in the genome.

Accepted Answer

A mutation is a change in a DNA sequence that is present in less than 1 percent of individuals in a population. Mutations can be beneficial, harmful or neutral and can be caused by errors during DNA replication, exposure to radiation or chemicals, or spontaneous DNA changes.

Question 17

Mutations and polymorphisms are both changes in a DNA sequence,but polymorphisms are more common because
A) they less severely affect the phenotype, so that individuals can reproduce and transmit them.
B) more people have them.
C) mutations are always lethal.
D) they more severely affect the phenotype, so that individuals cannot reproduce and transmit them.
E) mutations refer to a real situation, whereas a polymorphism is an idealized state that biologists hypothesized to explain genetic change.

Accepted Answer

Polymorphisms are more common because they are usually less severe and can be tolerated in individuals, allowing them to be passed down through generations. Mutations, on the other hand, may be lethal or cause significant health problems, making them less common in the population.

Question 18

The mutation that causes sickle cell disease
A) occurs in the same gene that, when mutant in a different way, causes beta thalassemia.
B) deletes two contiguous DNA bases.
C) results in a single DNA base change that does not alter the encoded amino acid.
D) changes a valine to a glutamic acid in the beta globin gene.
E) changes a glutamic acid to a valine in the alpha globin gene.

Accepted Answer

The mutation causing sickle cell disease occurs in the beta globin gene, which is the same gene that, when mutated differently, can cause beta thalassemia.

Question 19

A tautomer is
A) a mutagen.
B) an RNA base.
C) an alternate structure of a molecule.
D) a poison.
E) the type of bond that holds DNA bases together.

Accepted Answer

A tautomer is an alternate structure of a molecule that can interconvert through chemical reactions. This can happen within a single molecule or between two different molecules.

Question 20

In Huntington disease,the mutation causes the encoded protein to have a novel function from the wild type protein.This is an example of
A) a gain of function.
B) a loss of function.
C) a translocation of function.
D) a deletion.
E) a change in the genetic code.

Accepted Answer

In Huntington disease, the mutation causes the huntingtin protein to have a novel function that is not present in the wild type protein. Specifically, the mutated huntingtin protein has a longer polyglutamine tract than the wild type protein, which leads to the production of toxic protein aggregates that eventually cause neuronal cell death. This novel function represents a gain of function, as the mutated protein has acquired a new property that is not present in the wild type protein.

Quiz 12: Gene Mutation

A chemical or physical agent that causes mutations is called a

A germline mutation passes from generation to generation because it occurs during the DNA replication before

Mutations in the lamin A gene are responsible for very diverse disorders because

The first single-gene disorder for which the mechanism of mutation was understood was

A somatic mutation

A mutation in a collagen gene is likely to affect the phenotype because

Spontaneous mutation occurs when

Sanjay and Indira have thalassemia minor.Their young daughters are dizygotic (fraternal) twins.Malonie has thalassemia minor like her parents,but Jewel has the more severe thalassemia major.The more serious case most likely arose because

The chance that the average gene undergoes a spontaneous mutation is about 1 in

___ gene(s) encode chains of the same collagen molecule.

The parents-to-be were shocked when an ultrasound scan done in the second trimester of the pregnancy showed a fetus with obviously broken leg bones and ribs.The doctor diagnosed osteogenesis imperfecta.This is caused by a mutation in a gene that encodes

In Ehlers-Danlos syndrome type 1,collagen molecules are

An example of a beneficial mutation is

A man and woman of normal height have a son with achondroplasia.They want to have another child,and wonder what the risk is that he or she will also have this form of dwarfism.The risk is

Estimates of spontaneous mutation rates are made using dominant disorders because

A mutation is

Mutations and polymorphisms are both changes in a DNA sequence,but polymorphisms are more common because

The mutation that causes sickle cell disease

A tautomer is

In Huntington disease,the mutation causes the encoded protein to have a novel function from the wild type protein.This is an example of