Question 1

Unequal crossing over results in
A)an exchange between nonhomologous chromosomes.
B)a loss of genetic material.
C)a repair of UV-induced damage.
D)a production of eggs containing Y chromosomes.
E)a creation of deletions and duplications.

Accepted Answer

Unequal crossing over can result in deletion or duplication of genetic material due to unequal exchange of homologous chromosomes. This occurs when misaligned homologous chromosomes exchange unequal amounts of DNA during crossing over. As a result, the chromosome that gains extra genetic material will have a duplication, while the one that loses genetic material will have a deletion.

Question 2

Thymine dimers are caused by
A)X-rays.
B)free radicals such as oxygen.
C)EMS or NSG.
D)depurination.
E)UV light.

Accepted Answer

Thymine dimers are caused by UV light. When UV light hits the DNA molecule, it can cause two nearby thymine bases to bond to each other, forming a thymine dimer. This can lead to mutations or DNA damage. The other options (A, B, C, D) do not cause thymine dimers specifically.

Question 3

Assume that a wild-type sequence is 5'AGCCTAC3'.Indicate the sequence that might be produced by a transversion.
A)5'AGTCTAC3'
B)5'AGCCGCCGCCGCCTAC3'
C)5'AGCCCAC3'
D)5'ATCCTAC3'
E)5'AGCCTGC3'

Accepted Answer

A transversion is a substitution of a purine for a pyrimidine, or vice versa. In this case, the wild-type sequence has an A (a purine) at position 2 of the sequence. Choice D shows a substitution of this A for a T (a pyrimidine), making it a transversion.

Question 4

The term mutation refers to
A)only changes in the DNA that result in new phenotypes.
B)only changes in the DNA that result in novel proteins.
C)any change in the DNA of a cell.
D)a heritable change in the DNA of a cell.
E)any change in the cell that changes its survival chances.

Accepted Answer

Mutation refers to any heritable change in the DNA of a cell, which may or may not result in new phenotypes or novel proteins. Therefore, option D is the best choice. The other options are not entirely correct as they limit the definition of mutation to specific outcomes.

Question 5

A heritable change in DNA base sequence is called a
A)forward mutation.
B)reversion.
C)substitution.
D)deletion.
E)mutation

Accepted Answer

A heritable change in DNA base sequence is called a mutation. The other options describe specific types of mutations but may not encompass all possible heritable changes in DNA.

Question 6

The duplication of the triplet sequence CGG resulting in elongation or breakage of the X chromosome is termed
A)Barr-eyed.
B)Huntington's disease.
C)unequal crossing over
D)Fragile X syndrome.
E)Rhys syndrome

Accepted Answer

Duplication of the CGG triplet sequence in the FMR1 gene located on the X chromosome results in Fragile X Syndrome. This causes a range of developmental and intellectual disabilities.

Question 7

Which type of mutation is least likely to revert?
A)deletion
B)transition
C)transversion
D)insertion
E)All are equally likely

Accepted Answer

The answer of Which type of mutation is least likely...

Question 8

Replacing a thymine nucleotide with a guanine is an example of a
A)translocation.
B)transition.
C)transversion.
D)forward mutation.
E)reversion or reverse mutation

Accepted Answer

A transition is the replacement of a purine nucleotide (adenine or guanine) with another purine, or the replacement of a pyrimidine nucleotide (cytosine or thymine) with another pyrimidine. A transversion is the replacement of a purine with a pyrimidine or vice versa. In this case, replacing thymine (a pyrimidine) with guanine (a purine) is a transversion.

Question 9

If a man shows the premutation allele for Fragile X syndrome, what is the probability that he will pass it on to his son?
A)100%
B)75%
C)50%
D)25%
E)0%

Accepted Answer

Fragile X syndrome is an X-linked disorder. A man passes his Y chromosome to his sons, not his X chromosome, so he cannot pass the premutation allele to his sons.

Question 10

Assume that the mutation rate for a given gene is 5*10⁶ mutations per gene per generation.For that gene how many mutations would be expected if 10 million sperm are examined? A)none B)5*10⁶ C)5 D)50 E)500

Accepted Answer

The expected number of mutations is calculated by multiplying the mutation rate (5*10^-6) by the number of sperm (10 million), resulting in 50 mutations.

Question 11

A mutation in which parts of two nonhomologous chromosomes change places is called a(n)
A)translocation.
B)transition.
C)transversion.
D)insertion.
E)deletion.

Accepted Answer

A translocation is a mutation in which parts of two nonhomologous chromosomes break off and switch places. This can lead to gene disruption, altered gene expression, and other genetic abnormalities. The other choices (transition, transversion, insertion, deletion) refer to different types of point mutations, which involve changes to individual nucleotides rather than whole chromosome segments.

Question 12

In the Luria Delbruck fluctuation experiment, the bacteria + phage plates showed
A)all plates had some resistant colonies, some had very many.
B)some plates had no resistant colonies, a few plates had very many resistant colonies.
C)all plates had the same number of resistant colonies.
D)some plates had no resistant colonies; the plates that had resistant colonies all had the same number of resistant colonies.
E)phage caused mutations to occur in some of the plates but not in others

Accepted Answer

The Luria Delbruck fluctuation experiment showed that mutations occur randomly and are not induced by selective pressure. In the bacteria + phage plates, some plates had no resistant colonies, while a few plates had very many resistant colonies. This indicates that mutations occurred randomly in some plates but not in others. Therefore, the best choice is B.

Question 13

Replacing an adenine nucleotide with a guanine is an example of a
A)translocation.
B)transition.
C)transversion.
D)forward mutation.
E)reversion or reverse mutation

Accepted Answer

This substitution involves a change between two nitrogenous bases of the same type (purine), hence it is classified as a transition. A transversion involves a change between two nitrogenous bases of different types (purine and pyrimidine), which is not the case. The other options are not relevant to the specific type of substitution mentioned.

Question 14

The results of the Luria Delbruck fluctuation experiment indicated that
A)bacteria are naturally resistant to phage.
B)a low level of any bacterial population is naturally resistant to phage.
C)bacteria become resistant to phage by mutation when exposed to phage.
D)bacteria become resistant to phage by random spontaneous mutation.
E)the phage mutate to produce large plaques with sharp edges.

Accepted Answer

The Luria Delbruck fluctuation experiment demonstrated that bacterial resistance to phages was not a result of natural selection, but rather due to random spontaneous mutations that pre-existed exposure to the phage. This supports the idea that evolution can occur by chance events, rather than solely through natural selection.

Question 15

Assume that a researcher set out to duplicate the Luria Delbruck fluctuation experiment.This researcher planted twenty small flasks with bacteria from the same colony and let them grow overnight.The next morning the researcher noticed that all but one of the flasks had come open and were ruined.Not wishing to redo the experiment the researcher took bacteria samples from the one remaining intact flask and placed them on twenty phage plates.What results would you expect to see when the twenty phage plates are examined, and how would these results compare with those of the original Luria Delbruck fluctuation experiment?
A)Identical to the Luria Delbruck results, namely different numbers of resistant colonies.
B)Identical to the Luria Delbruck results, namely identical numbers of resistant colonies.
C)Not like the Luria Delbruck results, namely different numbers of resistant colonies.
D)Not like the Luria Delbruck results, namely identical numbers of resistant colonies.
E)Identical to the Luria Delbruck results, namely no resistant colonies.

Accepted Answer

The original Luria-Delbruck experiment showed variation in the number of resistant colonies due to random mutations. Since all samples in this scenario come from the same flask, they would likely have identical numbers of resistant colonies, unlike the original experiment.

Question 16

Consider the following results.When 50 million sperm were examined for a specific mutation, 100 mutations were found.Indicate the mutation rate for that gene. A)5*10⁶ B)50*10⁶ C)2*10⁶ D)2*10⁵ E)5*10⁵

Accepted Answer

The mutation rate can be calculated by dividing the number of mutations by the total number of sperm examined. In this case, the mutation rate would be 100/50,000,000 which simplifies to 2/1,000,000 or 2x10^-6. Choice C is the only option that matches this value.

Question 17

The heritable disorder Fragile X syndrome, a major cause of mental retardation, is caused by
A)production of enzymes that break the phosphate backbone.
B)UV light.
C)X-rays.
D)presence of an extra X chromosome in the sperm or egg
E)duplication of multiple three-nucleotide repeats.

Accepted Answer

Fragile X syndrome is caused by the expansion of the CGG trinucleotide repeat affecting the FMR1 gene on the X chromosome, leading to its dysfunction.

Question 18

Genes on the X chromosome of mammals and Drosophila are particularly suitable for genetic study because
A)males have only one X and most genes behave as haploids.
B)females have only one X and most genes behave as haploids.
C)the X chromosome is large and many more genes are located there.
D)when present as Barr bodies they are exposed for electron microscopic examination.
E)they behave as diploids in females.

Accepted Answer

In mammals, males have only one X chromosome and thus most genes on it behave as haploids. This makes it easier to study the inheritance and expression of traits linked to specific genes on the X chromosome. Similarly, in Drosophila, males have only one X chromosome and most genes on it behave as haploids, making it a useful model organism for studying genetics.

Question 19

The hydrolysis of a purine base from the deoxyribose-phosphate backbone is called
A)depurination.
B)deamination.
C)replica plating.
D)excision repair.
E)deletion.

Accepted Answer

The hydrolysis of a purine base, which is one of the two types of nitrogenous bases found in DNA, from the deoxyribose-phosphate backbone is called depurination. This can lead to the formation of an apurinic site, also known as an AP site, in the DNA strand.

Question 20

UV light is a mutagen that can cause
A)depurination.
B)deamination.
C)alkylation.
D)thymine dimers
E)oxidation.

Accepted Answer

UV light causes the formation of thymine dimers, which are covalent bonds between adjacent thymine nucleotides on the same DNA strand. This type of DNA damage can lead to mutations if not repaired properly. Depurination, deamination, alkylation, and oxidation are all types of chemical damage to DNA that can also cause mutations, but they are not directly caused by UV light.

Quiz 7: Anatomy and Function of a Gene: Dissection Through Mutation

Unequal crossing over results in

Thymine dimers are caused by

Assume that a wild-type sequence is 5'AGCCTAC3'.Indicate the sequence that might be produced by a transversion.

The term mutation refers to

A heritable change in DNA base sequence is called a

The duplication of the triplet sequence CGG resulting in elongation or breakage of the X chromosome is termed

Which type of mutation is least likely to revert?

Replacing a thymine nucleotide with a guanine is an example of a

If a man shows the premutation allele for Fragile X syndrome, what is the probability that he will pass it on to his son?

Assume that the mutation rate for a given gene is 5*106 mutations per gene per generation.For that gene how many mutations would be expected if 10 million sperm are examined?

A mutation in which parts of two nonhomologous chromosomes change places is called a(n)

In the Luria Delbruck fluctuation experiment, the bacteria + phage plates showed

Replacing an adenine nucleotide with a guanine is an example of a

The results of the Luria Delbruck fluctuation experiment indicated that

Consider the following results.When 50 million sperm were examined for a specific mutation, 100 mutations were found.Indicate the mutation rate for that gene.

The heritable disorder Fragile X syndrome, a major cause of mental retardation, is caused by

Genes on the X chromosome of mammals and Drosophila are particularly suitable for genetic study because

The hydrolysis of a purine base from the deoxyribose-phosphate backbone is called

UV light is a mutagen that can cause

Assume that the mutation rate for a given gene is 5*10⁶ mutations per gene per generation.For that gene how many mutations would be expected if 10 million sperm are examined?