Question 1

Beta-thalassemia is a disease that results from the reduction or absence of a functional $\beta$-globin gene.It results in patients that exhibit moderate to severe anemia,poor growth,and possibly skeletal abnormalities.Depending on how severe a patient presents,they may need regular to periodic blood transfusions throughout their life.It is known that there are various mechanisms of mutation that result in beta-thalassemia.You are studying a group of individuals with beta-thalassemia in order to better understand the disease.Upon sequencing the $\beta$-globin gene,you notice that only about half of the patients in your study have deletions in their $\beta$-globin gene.The other half has no abnormalities in the sequence of this gene.From other tests,you know that these patients do in fact have beta-thalassemia,as they are deficient in $\beta$-globin protein and other members of their families also suffer from similar conditions.What is the most likely explanation for the presence of this genetic disease in these people?
A)There is a mutation in the promoter of the $\beta$-globin gene preventing adequate expression of the protein.
B)There was an inversion with a splice point within the $\beta$-globin gene.
C)There is a microorganism,such as a virus,that is causing these symptoms.
D)The patients actually have bone marrow cancer that is causing these symptoms.
E)The patients actually have sickle-cell anemia.

Accepted Answer

The presence of beta-thalassemia in individuals with normal sequence of the F1F1F1S1F1F1F10-globin gene suggests that there may be mutations in the promoter region of the gene, preventing adequate expression of the protein. This could result in reduced levels of the protein and the symptoms observed in these patients.

Question 2

Women are cautioned against having children later in life because the incidence of Down syndrome (trisomy 21)increases rapidly with age.What is the best explanation for this phenomenon?
A)Somatic mutations accumulate as a woman gets older,leading to changes in the uterine environment that cause down syndrome.
B)Germ line mutations accumulate as a woman ages,so a larger percentage of her eggs have mutations.
C)Germ line mutations accumulate as a woman gets older,leading to changes in the uterine environment that cause down syndrome.
D)Somatic mutations accumulate as a woman ages,so a larger percentage of her eggs have mutations.
E)Somatic mutations accumulate as a woman ages,so the developing embryo is more likely to acquire mutations that lead to down syndromE.

Accepted Answer

Germ line mutations, specifically nondisjunction events that lead to an extra copy of chromosome 21, are more likely to occur in the eggs of older women, increasing the risk of Down syndrome.

Question 3

Study the mutations described below and determine which one is most likely to lead to cancer.
A)A mutation in the Ras protein increases its affinity for GDP.
B)A mutation in the Ras protein that prevents GTP hydrolysis.
C)A mutation in a receptor protein that decreases its affinity for a growth factor.
D)A mutation in a transcription factor that prevents it from binding to the DNA to transcribe genes that promote cell division.
E)All of these mutations might lead to cancer.

Accepted Answer

A mutation in the Ras protein that prevents GTP hydrolysis results in the constant activation of downstream signaling pathways, which can lead to uncontrolled cell growth and division, ultimately resulting in cancer. The other mutations described can also have important effects on cell signaling and growth, but are less likely to lead to cancer.

Question 4

Study the loci that have been identified on the two non-homologous chromosomes below and determine what mutation is the most likely to lead to cancer. 
A)A reciprocal translocation switches the entire long arm of one chromosome with the entire long arm of the other chromosome.
B)An inversion switches the position of the blue and purple genes.
C)An inversion switches the position of the red and orange regions.
D)A deletion occurs in the green gene,so that it no longer binds to org,but instead binds to the purple gene.
E)A deletion occurs in the green gene,so that it no longer binds to org,but instead binds to the blue genE.

Accepted Answer

The deletion of the green gene and its interaction with the purple gene could potentially disrupt normal cellular processes and lead to uncontrolled cell growth, which is a hallmark of cancer. The other options (A, B, C, and E) may cause changes in gene order or expression, but they are less likely to directly lead to cancer.

Question 5

Study the figure below of two non-homologous chromosomes.Several loci have been identified on these chromosomes.Next,study the changes that have taken place,resulting in the mutated chromosomes,and determine which mutated chromosomes are the most likely to lead to cancer?
Normal Chromosomes 
Mutated Chromosomes 
A)A
B)B
C)C
D)D
E)A,B,C,and D are all mutations,so they will all lead to cancer

Accepted Answer

The answer of Study the figure below of two non-homologous...

Question 6

Study the mutations below and determine which is the most likely to lead to cancer.
A)A mutation that increases the affinity of Rb for E2F
B)A mutation that prevents the phosphorylation of Rb
C)A mutation that prevents E2F from associating with DNA
D)A mutation that caused the cyclin-dependent kinase that interacts with Rb to be overactive
E)All of these are mutations that would lead to cancer

Accepted Answer

The overactivity of cyclin-dependent kinase that interacts with Rb would lead to a hyperphosphorylated state of Rb, which would release E2F and allow for uncontrolled cell proliferation, leading to cancer. The other mutations listed may disrupt normal cell cycle regulation, but are less likely to lead to cancer.

Question 7

You are a brilliant graduate student and you are skeptical of the results found by the Lederbergs.You decide to repeat their experiment,but you do not have ready access to T1 bacteriophage.What might you use instead?
A)HIV virus
B)HPV virus
C)X-gal - the substrate of the enzyme $\beta$-galactosidase
D)Ampicillin - an antibiotic
E)Salmonella bacteria

Accepted Answer

Ampicillin, an antibiotic, can be used to test for bacterial resistance, similar to how the Lederbergs used T1 bacteriophage to test for bacterial mutations.

Question 8

The Lederbergs conducted an experiment that showed that mutations were random events.The alternative view,proposed by Lamarck,predicted that organisms changed in response to their environment and would pass on that change to their offspring.If Lamarck's hypothesis was correct,what results would you expect the Lederbergs to have seen?
A)There would have been no bacterial colonies on the master plate or on the plates with the T1 phage.
B)There would have been no bacterial colonies on the master plate,but there would have been copious amouts on the plates with the T1 phage.
C)There would be bacterial colonies on the master plate and there would be a few colonies growing on plates with the T1 phage,but the two plates with T1 phage would have colonies growing in different locations.
D)There would have been bacterial colonies on the master plate and all of those colonies would be present on the plates with the T1 phage.
E)You would need to design a completely different experiment to test Lamarck's hypothesis.

Accepted Answer

If Lamarck's hypothesis was correct, bacteria would develop resistance in response to the presence of the T1 phage, leading to colonies appearing in different locations on each plate with the phage.

Quiz 12: Mutation, DNA Repair, and Cancer

Women are cautioned against having children later in life because the incidence of Down syndrome (trisomy 21) increases rapidly with age.What is the best explanation for this phenomenon?

Study the mutations described below and determine which one is most likely to lead to cancer.

Study the loci that have been identified on the two non-homologous chromosomes below and determine what mutation is the most likely to lead to cancer.

Study the mutations below and determine which is the most likely to lead to cancer.

You are a brilliant graduate student and you are skeptical of the results found by the Lederbergs.You decide to repeat their experiment,but you do not have ready access to T1 bacteriophage.What might you use instead?