Question 1

Sickle-cell gene therapy in clinical trials

Accepted Answer

Gene therapy for sickle-cell disease has shown promising results, with the therapy leading to the expression of the correct form of hemoglobin protein, which is crucial for overcoming the symptoms of the disease.

Question 2

Which of following best describes the genetic applications of using CRISPR?

Accepted Answer

CRISPR technology is versatile and can be used for various genetic modifications, including targeting and removing DNA sequences, as well as replacing them with desired sequences, depending on the specific application.

Question 3

Several different researchers contributed to the study of the structure of DNA. What did Oswald Avery contribute?

Accepted Answer

Oswald Avery demonstrated that DNA is the genetic material by showing that transformation of bacteria did not occur when DNase enzyme was added, which destroyed the DNA.

Question 4

Several different researchers contributed to the study of the structure of DNA. What did Rosalind Franklin contribute?

Accepted Answer

Rosalind Franklin's work with X-ray crystallography provided critical evidence that DNA has a helical structure. Her photographs, particularly Photo 51, were key in determining the double helix structure of DNA.

Question 5

Several different researchers contributed to the study of the structure of DNA. What did Erwin Chargaff contribute?

Accepted Answer

Erwin Chargaff discovered that in DNA, the amount of adenine (A) is approximately equal to the amount of thymine (T), and the amount of guanine (G) is approximately equal to the amount of cytosine (C). This finding, known as Chargaff's rules, was crucial for the understanding of the base pairing mechanism in the DNA double helix structure.

Question 6

Several different researchers contributed to the study of the structure of DNA. What did Frederick Griffith contribute?

Accepted Answer

Frederick Griffith discovered the phenomenon of transformation in bacteria, demonstrating that a "transforming factor" could change the characteristics of bacteria, leading to the concept that this factor was related to genetic information.

Question 7

PCR mimics DNA replication. Which of the following steps of PCR corresponds with the annealing process in DNA replication?

Accepted Answer

The annealing process in PCR is similar to the role of primers in DNA replication, where a primer binds to the template strand to provide a starting point for DNA polymerase to begin synthesizing the new strand.

Question 8

PCR mimics DNA replication. Which of the following steps of PCR corresponds with the denaturing process in DNA replication?

Accepted Answer

In DNA replication, the enzyme helicase unwinds the DNA double helix and separates the two strands by breaking the hydrogen bonds between them, a process that corresponds to the denaturing step in PCR where the DNA double helix is separated into two single strands by heating.

Question 9

PCR mimics DNA replication. Which of the following steps of PCR corresponds with the extension process in DNA replication?

Accepted Answer

During the extension step of PCR, DNA polymerase synthesizes a new strand of DNA by adding nucleotides to the 3' end of the primer, which is analogous to the extension process in DNA replication where DNA polymerase synthesizes the new daughter strand.

Question 10

Which event (or events) occur in the prophase I phase of meiosis I?

Accepted Answer

During prophase I of meiosis I, chromosomes condense, homologous chromosomes pair up to form tetrads, and crossing over, the exchange of genetic material between homologous chromosomes, occurs. This phase is crucial for genetic diversity.

Question 11

Which event (or events) occur in the anaphase I phase of meiosis I?

Accepted Answer

In anaphase I of meiosis I, homologous chromosomes are separated and pulled to opposite poles of the cell, unlike in mitosis where sister chromatids are separated.

Question 12

Which event (or events) occur in the metaphase I phase of meiosis I?

Accepted Answer

In metaphase I of meiosis I, tetrads (pairs of homologous chromosomes) align along the metaphase plate in preparation for their separation to opposite poles.

Question 13

Which event (or events) occur in the telophase I phase of meiosis I?

Accepted Answer

During telophase I of meiosis I, the chromosomes that have been separated reach the poles of the cell, and the cell starts to divide into two. This phase is characterized by the reformation of the nuclear membranes around the separated chromosomes and the beginning of the cytoplasmic division, often visible as the cleavage furrow. Choices A, B, and C describe events that occur during earlier phases of meiosis I.

Question 14

Which event (or events) occur in the metaphase II phase of meiosis II?

Accepted Answer

During metaphase II of meiosis II, sister chromatids (not yet separated into individual chromosomes) align along the metaphase plate in preparation for their separation to opposite poles, which occurs in the subsequent anaphase II. This ensures that each daughter cell receives an equal and accurate distribution of chromosomes.

Question 15

Which event (or events) occur in the telophase II phase of meiosis II?

Accepted Answer

In telophase II of meiosis II, the chromosomes have already been separated into sister chromatids during anaphase II. The events that occur during telophase II include the reformation of the nuclear membrane around the separated chromatids and the beginning of cytokinesis, which is often evidenced by the development of a cleavage furrow in animal cells. This phase essentially prepares the cells to divide into two new cells, completing the process of meiosis II.

Question 16

Which event (or events) occur in the anaphase II phase of meiosis II?

Accepted Answer

During anaphase II of meiosis II, sister chromatids are separated and pulled to opposite poles of the cell. This is a key step in ensuring that each daughter cell receives an equal and accurate distribution of genetic material.

Question 17

Which event (or events) occur in the prophase II phase of meiosis II?

Accepted Answer

During prophase II, the chromosomes condense again following a brief period of decondensation and the nuclear envelope breaks down, preparing the cell for the second meiotic division.

Question 18

There are two main forms of non-Mendelian dominance. In ______, as observed in familial hypercholesterolemia, the dominant allele does not completely mask the recessive allele. In ______, as observed in AB blood type, two dominant alleles are expressed for the same phenotype.

Accepted Answer

Incomplete dominance is when the dominant allele does not completely mask the recessive allele, resulting in a phenotype that is a blend of the two. Codominance occurs when both alleles in a heterozygote are fully expressed, such as in the AB blood type, where both A and B alleles are expressed equally.

Question 19

Which of the following is an example of a human phenotype determined by epistatic interaction?

Accepted Answer

Eye color is an example of a human phenotype determined by epistatic interaction, where multiple genes interact to determine the final phenotype. This interaction can result in a wide range of eye colors beyond the simple brown/blue inheritance pattern once thought to be the case.

Question 20

Sickle-cell anemia limits its effects within the body to the respiratory and circulatory systems.

Accepted Answer

Sickle-cell anemia affects multiple systems beyond the respiratory and circulatory systems, including the immune system, causing increased susceptibility to infections, and can lead to complications in organs such as the spleen, liver, and kidneys.

Quiz 8: Characteristics, Functions, and Analysis of Genetic Diseases and DNA