MSN Exam for Genes and Heredity

Text Mode – Text version of the exam

Questions

1. Let’s take an intriguing journey into the world of biomolecules. Among the various RNA varieties listed below, can you identify which one tends to be the most petite?

A. pRNA
B. rRNA
C. tRNA
D. mRNA

2. Embarking on a microscopic adventure into the realm of nucleic acids, can you identify the intruder who isn’t actually a member of the pyrimidine family?

A. Thymine (T)
B. Guanine (G)
C. Cytosine (C)
D. Uracil (U)

3. Diving into the cellular world, we encounter an intriguing genetic code. Among the following sequences, can you identify which usually signals the beginning of the mRNA translation journey?

A. AGU
B. UGA
C. AUG
D. UAA

4. Stepping into the lab, we encounter an assortment of bioanalytical techniques. Among these, which one would you associate with the Western blot?

A. Combination of DNA and RNA.
B. RNA Transcription.
C. Polymerase Chain Reaction.
D. Pairing of Antibody and Protein.

5. Within the global population, the occurrence of certain genetic conditions can vary widely. For cystic fibrosis, can you deduce its approximate prevalence ratio?

A. 1: 25,000
B. 1: 3,000
C. 1: 900
D. 1: 2,000

6. Get ready for an intriguing question about the remarkable world of genetics! Can you identify which chromosome is associated with Down syndrome due to a genetic irregularity?

A. XIIX
B. XXIII
C. XXI
D. XVI

7. Let’s dive into the realm of population genetics! Can you tell which of these options truly embodies an attribute of the Hardy-Weinberg principle?

A. The location under consideration experiences no genotype selection.
B. Interspecies mating happens at a consistent pace.
C. The spot in question witnesses a genetic mutation.
D. Migration greatly impacts the population dynamics.

8. In the series of events in a cell’s life cycle, which specific phase typically comes immediately before the process of Mitosis?

A. S Phase
B. G2 Phase
C. G0 Phase
D. E Phase

9. Can you identify the correct base pairing in the options below?

A. Adenine-Guanine
B. Cytosine-Guanine
C. Adenine-Thymine
D. Guanine-Thymine

10. Among the following characteristics, can you single out the one that is NOT typically associated with the clinical presentation of Hurler’s syndrome?

A. Associated with delayed mental development.
B. An ailment inherited in an autosomal recessive manner.
C. Dysfunction in corneal activities.
D. Spasticity

11. Can you identify which compound listed below is not synthesized from the amino acid Tryptophan?

A. Creatine
B. Melatonin
C. Niacin
D. Serotonin

12. Which of the following attributes does not apply to Sickle Cell Anemia?

A. It’s an autosomal dominant condition.
B. It’s more prevalent among African Americans.
C. It’s associated with a mutation in beta-globin.
D. It causes severe chronic pain.

13. Identify the feature that doesn’t correspond with Fabry’s disease.

A. It’s an X-linked disease.
B. It manifests profound muscular weakness.
C. It results in elevated levels of ceramide trihexoside.
D. It leads to reduced levels of alpha-galactosidase A.

14. Which aspect below does not align with the principles of a Southern blot technique?

A. The application of a filter and film combination.
B. The process of DNA hybridization.
C. The utilization of a DNA sample.
D. Initiated by antigen/antibody interactions.

15. Among the options provided, which is not classified as an activated carrier molecule?

A. Thiamine pyrophosphate (TPP)
B. Nicotinamide adenine dinucleotide (NAD+)
C. Guanosine monophosphate (GMP)
D. Adenosine triphosphate (ATP)

16. Identify the symptom that isn’t typically associated with Krabbe’s disease.

A. Nausea
B. It’s an autosomal recessive condition.
C. Muscular stiffness or spasticity.
D. Deficits in the optic nerve function.

17. Which feature does not appropriately describe S-adenosyl-methionine?

A. It’s a byproduct of the combination of Methionine and ATP.
B. It may be associated with phosphocreatine.
C. It’s considered a rate-limiting enzyme of glycolysis.
D. It improves kidney function.

18. Upon completion of the tricarboxylic acid (TCA) cycle, how many molecules of NADH are typically produced?

A. Eight
B. Three
C. Four
D. Five

19. Pompe’s disease is classified as which type of glycogen storage disease?

A. Type III
B. Type V
C. Type I
D. Type II

20. In the process of converting pyruvate into glucose, how many molecules of ATP are typically required?

A. Six
B. Eight
C. Five
D. Seven

 

Answers & Rationales

1. Correct answer:

C. tRNA. Transfer RNA (tRNA) is generally considered the smallest of the RNA types mentioned, with a size of approximately 73-94 nucleotides. This molecule’s main function is to carry amino acids to the ribosome during protein synthesis, where it decodes the mRNA’s message. Its small size and distinctive “cloverleaf” structure are important features that allow it to bind to an amino acid on one end, and an mRNA codon on the other, thus translating the genetic code into a sequence of amino acids.

Incorrect answer options:

A. pRNA. The term “pRNA” usually refers to “packaging RNA”, a type of RNA involved in phage assembly. Its size can vary, but it’s typically larger than tRNA.

B. rRNA. Ribosomal RNA (rRNA) forms the integral part of the ribosome, the protein manufacturing machinery of the cell. This type of RNA is significantly larger than tRNA. For example, in eukaryotes, 28S, 18S, 5.8S and 5S rRNA components form the ribosomal subunits.

D. mRNA. Messenger RNA (mRNA) carries the genetic information from DNA in the nucleus to the cytoplasm, where it directs protein synthesis. The size of mRNA molecules can vary greatly depending on the gene it’s transcribing, but generally, they are much larger than tRNA because they have to carry the complete information for the synthesis of a protein, which typically consists of hundreds of amino acids.

2. Correct answer:

B. Guanine (G). Guanine is a purine, not a pyrimidine. In nucleic acids, the two major types of nitrogenous bases are purines and pyrimidines. Purines include adenine (A) and guanine (G), while pyrimidines include cytosine (C), thymine (T), and uracil (U). Guanine, being a purine, consists of a two-ring structure (a six-membered ring fused to a five-membered ring), which is larger and more complex than the single six-membered ring structure of the pyrimidines.

Incorrect answer options:

A. Thymine (T). Thymine is indeed a pyrimidine. It pairs with adenine in DNA through two hydrogen bonds, aiding in stabilizing the nucleic acid structures.

C. Cytosine (C). Cytosine is a pyrimidine. It pairs with guanine in both DNA and RNA to maintain the integrity of the genetic information.

D. Uracil (U). Uracil is a pyrimidine that is found in RNA, where it replaces thymine and pairs with adenine.

3. Correct answer:

C. AUG. This sequence is generally recognized as the start codon in the process of translation. The AUG codon codes for the amino acid methionine in eukaryotes and a modified methionine (formylmethionine) in prokaryotes. This signals to the cellular machinery to begin assembling a protein at that position on the mRNA molecule. Its recognition is crucial for the proper initiation of translation.

Incorrect answer options:

A. AGU. This is a codon for the amino acid serine. It does not signify the start of translation.

B. UGA. This is one of the three “stop” codons (along with UAA and UAG). These do not code for an amino acid, but instead signal the end of translation, instructing the protein synthesis machinery to release the completed protein.

D. UAA. Like UGA, this is also a “stop” codon. It signals the termination of protein synthesis.

4. Correct answer:

D. Pairing of Antibody and Protein. The Western blot technique involves the separation of proteins by gel electrophoresis, transfer of the separated proteins onto a membrane, and detection of the target protein by using a specific antibody. The antibody-protein interaction allows for the identification and quantification of a specific protein in a complex sample. This technique can also provide information about a protein’s size and, in some cases, its post-translational modifications.

Incorrect answer options:

A. Combination of DNA and RNA. While this can occur in molecular biology (such as during the process of transcription), it is not specifically related to the Western blot technique.

B. RNA Transcription. This is a process in gene expression where a segment of DNA is copied into RNA by the enzyme RNA polymerase. While a key part of molecular biology, it is not directly related to Western blotting.

C. Polymerase Chain Reaction (PCR). PCR is a technique used to amplify a specific DNA segment, making it extremely useful in various areas such as genetic testing, criminal forensics, and clinical diagnostics. However, it is not associated with the Western blot, which is a protein-detection method.

5. Correct answer:

B. 1: 3,000. Cystic fibrosis (CF) is one of the most common lethal genetic disorders in populations of Northern European descent. It’s estimated that CF affects approximately 1 in every 2,500 to 3,500 white newborns. Prevalence in other populations can vary; for example, CF is much less common in African American and Asian populations.

Incorrect answer options:

A. 1: 25,000. This prevalence would represent a less common genetic condition.

C. 1: 900. This number would represent a more common genetic condition than cystic fibrosis.

D. 1: 2,000. This number is a bit higher than the typical estimated prevalence of cystic fibrosis, but it’s closer to the true value than the other incorrect options.

6. Correct answer:

C. XXI. Down syndrome is a genetic condition that occurs when an individual has three copies of chromosome 21, rather than the usual two. This condition is also referred to as Trisomy 21. Down syndrome leads to a combination of distinctive physical features, potential health complications, and degrees of intellectual disability.

Incorrect answer options:

A. XIIX. There is no chromosome designated “XIIX” in the human genome. The human genome contains 23 pairs of chromosomes, numbered from 1 to 22 in decreasing size order, with the 23rd pair being the sex chromosomes X and Y.

B. XXIII. This represents a misunderstanding. In humans, the 23rd pair of chromosomes determines the sex of an individual and is designated as either XX (for females) or XY (for males).

D. XVI. This is chromosome 16. While important, and certain disorders are associated with this chromosome (for example, Alpha-thalassemia is associated with mutations on chromosome 16), it’s not associated with Down syndrome.

7. Correct answer:

A. The location under consideration experiences no genotype selection. One of the main assumptions of the Hardy-Weinberg principle, which describes the behavior of genetic variants in a population, is that no selection occurs, meaning all genotypes in the population reproduce at the same rate. This principle helps to provide a baseline from which we can understand how real-world populations evolve and why they might differ from this idealized state.

Incorrect answer options:

B. Interspecies mating happens at a consistent pace. Interspecies mating is not a part of the Hardy-Weinberg principle, which is more concerned with the genetic makeup within a single population of a species. Interspecies mating would likely introduce new alleles into a population, disrupting Hardy-Weinberg equilibrium.

C. The spot in question witnesses a genetic mutation. Actually, one of the assumptions of the Hardy-Weinberg principle is that no mutation occurs. Mutations introduce new alleles into a population and can change the allele frequencies, violating the principle’s conditions.

D. Migration greatly impacts the population dynamics. Migration, or gene flow, is also excluded in the assumptions of the Hardy-Weinberg principle. The movement of individuals (and their genes) into or out of a population can disrupt the genetic equilibrium predicted by the principle.

8. Correct answer:

B. G2 Phase. The cell cycle consists of interphase (which includes the G1 phase, S phase, and G2 phase) and the mitotic phase. During the G1 phase, the cell grows and prepares for DNA replication, which takes place in the S phase. After DNA replication, the cell enters the G2 phase, where it continues to grow and prepares for division. Mitosis (and cytokinesis, which often overlaps with it) follows the G2 phase.

Incorrect answer options:

A. S Phase. This is the phase in which the cell replicates its DNA. The S phase precedes the G2 phase.

C. G0 Phase. This is a state of quiescence that cells may enter from the G1 phase. Cells in the G0 phase have left the cell cycle and have ceased dividing. If a cell in G0 returns to the cell cycle, it would enter the G1 phase.

D. E Phase. There is no phase of the cell cycle known as the “E Phase” in standard biological terminology.

9. Correct answer:

B. Cytosine-Guanine. In the structure of DNA, the nucleotide cytosine (C) pairs with guanine (G) via three hydrogen bonds.

Incorrect answer options:

A. Adenine-Guanine. Adenine and Guanine are both purines and do not pair with each other in the DNA structure. Adenine forms a base pair with Thymine, while Guanine pairs with Cytosine.

C. Adenine-Thymine. While this is a correct pairing in DNA, it’s not the right answer in this context as the question asks for a single correct answer.

D. Guanine-Thymine. This is an incorrect base pairing. Guanine forms a base pair with Cytosine in DNA.

10. Correct answer:

D. Spasticity. Spasticity, which refers to a state of increased muscle tone leading to stiff, uncontrolled movements, is not typically associated with Hurler’s syndrome, also known as mucopolysaccharidosis type I (MPS I). MPS I is a lysosomal storage disease that affects multiple systems in the body, but it does not typically cause spasticity.

Incorrect answer options:

A. Associated with delayed mental development. This statement is true as Hurler’s syndrome is indeed associated with delayed mental development. Children with this condition typically experience progressive cognitive decline, often beginning in the first year or two of life.

B. An ailment inherited in an autosomal recessive manner. This statement is true. Hurler’s syndrome is an autosomal recessive disorder, meaning that the disease only manifests if a child inherits two copies of the defective gene, one from each parent. Parents are usually carriers of the condition, possessing one defective gene but not exhibiting symptoms themselves.

C. Dysfunction in corneal activities. This statement is also true. Individuals with Hurler’s syndrome often have corneal clouding due to the buildup of glycosaminoglycans, substances that the body cannot break down because of an enzyme deficiency. This buildup can lead to a range of visual disturbances.

11. Correct answer:

A. Creatine. Creatine is not synthesized from the amino acid tryptophan. It is primarily synthesized in the liver and kidneys from the amino acids glycine, arginine, and methionine. Creatine plays a key role in energy production in muscle cells.

Incorrect answer options:

B. Melatonin. This is synthesized from tryptophan. The conversion involves several steps, starting with the conversion of tryptophan to 5-hydroxytryptophan, then to serotonin, and finally to melatonin. Melatonin plays a vital role in regulating the body’s sleep-wake cycle.

C. Niacin. Niacin, also known as vitamin B3, can be synthesized in the body from tryptophan, although it can also be obtained directly from the diet. Tryptophan is converted to niacin through a multi-step process that also involves vitamin B6 and iron.

D. Serotonin. Serotonin, a key neurotransmitter in the brain, is synthesized directly from tryptophan. The conversion involves a two-step process, with tryptophan first being converted to 5-hydroxytryptophan by the enzyme tryptophan hydroxylase, and then to serotonin by the enzyme aromatic amino acid decarboxylase.

12. Correct answer:

A. It’s an autosomal dominant condition. Sickle cell anemia is actually an autosomal recessive condition, not dominant. This means that a person must inherit two copies of the defective gene, one from each parent, in order to develop the disease. Individuals who inherit only one copy of the gene are carriers of the trait but do not usually exhibit symptoms of the disease.

Incorrect answer options:

B. It’s more prevalent among African Americans. This is correct. Sickle cell anemia is more common in people of African descent, but it can affect any race or ethnicity. It’s estimated that sickle cell anemia affects 1 in 365 African American births.

C. It’s associated with a mutation in beta-globin. This is also correct. Sickle cell anemia is caused by a mutation in the HBB gene, which provides instructions for making a part of hemoglobin, the protein in red blood cells that carries oxygen. Specifically, it affects the beta-globin subunit of hemoglobin.

D. It causes severe chronic pain. This statement is also correct. The hallmark symptom of sickle cell anemia is episodes of pain, known as sickle cell crises. These crises occur when the abnormally shaped red blood cells block small blood vessels, preventing oxygen from reaching tissues. This can cause pain in any part of the body, depending on where the blockage occurs.

13. Correct answer:

B. It manifests profound muscular weakness. Fabry’s disease, also known as Anderson-Fabry disease, is not typically associated with profound muscular weakness. Instead, the disease is characterized by episodes of pain, especially in the hands and feet, and small, dark red spots on the skin. Other symptoms may include gastrointestinal problems, decreased sweating, and problems with the heart, kidneys, and nervous system.

Incorrect answer options:

A. It’s an X-linked disease. This statement is true. Fabry’s disease is indeed an X-linked genetic disorder, meaning that the defective gene causing the condition is located on the X chromosome. Males are more severely affected, while females may have milder symptoms or be asymptomatic carriers.

C. It results in elevated levels of ceramide trihexoside. This is also true. In Fabry’s disease, a deficiency of the enzyme alpha-galactosidase A leads to an accumulation of globotriaosylceramide (also known as ceramide trihexoside) in the body’s cells, resulting in the symptoms of the disease.

D. It leads to reduced levels of alpha-galactosidase A. This statement is also correct. Fabry’s disease is caused by mutations in the GLA gene, which provides instructions for making the enzyme alpha-galactosidase A. This enzyme deficiency is responsible for the build-up of globotriaosylceramide, the primary cause of the disease’s symptoms.

14. Correct answer:

D. Initiated by antigen/antibody interactions. Southern blotting is a technique used in molecular biology for detection of a specific DNA sequence in DNA samples. It does not involve antigen/antibody interactions. This principle is more aligned with techniques such as ELISA or Western blotting, which are used to detect proteins (antigens) using antibodies.

Southern blotting involves the transfer of DNA fragments from an agarose gel onto a filter membrane, followed by hybridization with a labeled probe that is complementary to the target DNA sequence. The filter and film combination is used to visualize the DNA fragments that have hybridized with the probe.

Incorrect answer options:

A. The application of a filter and film combination. This is a correct aspect of Southern blotting. After the DNA fragments have been transferred to the filter membrane, a film is applied over the membrane. The film is then developed to visualize the DNA fragments that have hybridized with the probe.

B. The process of DNA hybridization. This is a key step in Southern blotting. The probe that is used in Southern blotting is designed to be complementary to the target DNA sequence. When the probe is added to the filter membrane, it will hybridize (bind) to the target DNA sequence.

C. The utilization of a DNA sample. This is the starting material for Southern blotting. The DNA sample is digested with restriction enzymes to create DNA fragments, which are then separated by size using gel electrophoresis.

15. Correct answer:

C. Guanosine monophosphate (GMP). GMP is a nucleotide, not an activated carrier molecule. Activated carrier molecules are small organic molecules that carry and transfer chemical groups, electrons, or protons to facilitate reactions in metabolic pathways. GMP, on the other hand, is a building block of RNA and does not function as a carrier molecule.

Incorrect answer options:

A. Thiamine pyrophosphate (TPP) is an activated carrier molecule. It is the active form of vitamin B1 (thiamine) and it carries and transfers two-carbon units in several important metabolic reactions.

B. Nicotinamide adenine dinucleotide (NAD+) is an activated carrier molecule. It carries and transfers electrons in many reactions, particularly in pathways involved in energy production such as glycolysis, the citric acid cycle, and oxidative phosphorylation.

D. Adenosine triphosphate (ATP) is an activated carrier molecule. It carries and transfers phosphate groups. ATP is often referred to as the “energy currency” of the cell because the transfer of a phosphate group from ATP to another molecule (a process called phosphorylation) is frequently coupled to reactions that require energy.

16. Correct answer:

A. Nausea. Krabbe’s disease, also known as globoid cell leukodystrophy, is a rare, inherited degenerative disorder of the nervous system. It primarily affects the white matter of the brain, leading to a variety of neurological symptoms. While it can cause a wide range of symptoms, nausea is not typically associated with Krabbe’s disease.

Krabbe’s disease is characterized by symptoms such as irritability, muscle weakness, feeding difficulties, episodes of fever without any sign of infection, and developmental delay. As the disease progresses, symptoms may include muscle stiffness or spasticity, seizures, hearing and vision loss, and intellectual disability.

Incorrect answer options:

B. It’s an autosomal recessive condition. This is true. Krabbe’s disease is inherited in an autosomal recessive manner, meaning that an individual must inherit two copies of the defective gene, one from each parent, in order to develop the disease.

C. Muscular stiffness or spasticity. This is a common symptom of Krabbe’s disease. The disease affects the nervous system, leading to a variety of neurological symptoms including muscle stiffness or spasticity.

D. Deficits in the optic nerve function. This is also a common symptom of Krabbe’s disease. The disease can cause damage to the optic nerve, leading to vision loss.

17. Correct answer:

C. It’s considered a rate-limiting enzyme of glycolysis. S-adenosylmethionine (SAMe) is not an enzyme, but rather a molecule that serves as a primary methyl group donor in a variety of biochemical reactions in the body. It is not involved in the rate-limiting steps of glycolysis. The rate-limiting enzymes of glycolysis are hexokinase, phosphofructokinase, and pyruvate kinase.

Incorrect answer options:

A. It’s a byproduct of the combination of Methionine and ATP. This is true. SAMe is synthesized in the body from the amino acid methionine and adenosine triphosphate (ATP).

B. It may be associated with phosphocreatine. This is also true. SAMe is involved in the synthesis of creatine, which can be converted to phosphocreatine in the body. Phosphocreatine plays a key role in energy storage in muscle cells.

D. It improves kidney function. While the role of SAMe in kidney function is not fully understood, some research suggests that it may have beneficial effects. For example, SAMe has been shown to have antioxidant properties and may help to protect against oxidative damage in the kidneys.

18. Correct answer:

B. Three. The tricarboxylic acid (TCA) cycle, also known as the citric acid cycle or Krebs cycle, is a series of chemical reactions used by all aerobic organisms to generate energy. For each round of the TCA cycle, three molecules of NADH are produced. These are generated in the following steps: the conversion of isocitrate to α-ketoglutarate, the conversion of α-ketoglutarate to succinyl-CoA, and the conversion of malate to oxaloacetate.

Incorrect answer options:

A. Eight. This is not correct. For each round of the TCA cycle, only three molecules of NADH are produced.

C. Four. This is not correct. While four molecules of NADH are produced per glucose molecule (since glucose is split into two pyruvate molecules, each of which enters the TCA cycle separately), only three NADH molecules are produced per round of the TCA cycle.

D. Five. This is not correct. Only three molecules of NADH are produced per round of the TCA cycle.

19. Correct answer:

D. Type II. Pompe’s disease, also known as glycogen storage disease type II, is a rare inherited disorder characterized by the buildup of a complex sugar called glycogen in the body’s cells. The accumulation of glycogen in certain organs and tissues, especially muscles, impairs their ability to function normally.

Incorrect answer options:

A. Type III. This is known as Cori’s disease or Forbes disease. It is caused by the deficiency of the enzyme amylo-1,6-glucosidase, which is involved in the breakdown of glycogen.

B. Type V. This is known as McArdle’s disease. It is caused by a deficiency of the enzyme muscle phosphorylase, which is needed for the breakdown of glycogen in muscle cells.

C. Type I. This is known as Von Gierke’s disease. It is caused by a deficiency of the enzyme glucose-6-phosphatase, which is necessary for the production of glucose from glycogen and other precursors.

20. Correct answer:

A. Six. The process of converting pyruvate into glucose is known as gluconeogenesis. This is a metabolic pathway that results in the generation of glucose from non-carbohydrate carbon substrates. It is a complex process that involves several steps and the consumption of energy in the form of ATP. For each molecule of glucose produced, a total of six molecules of ATP are required.

Incorrect answer options:

B. Eight. This is not correct. Only six molecules of ATP are required for the conversion of pyruvate into glucose.

C. Five. This is not correct. The process of gluconeogenesis requires more energy, specifically six molecules of ATP for each molecule of glucose produced.

D. Seven. This is not correct. Only six molecules of ATP are required for the conversion of pyruvate into glucose.