Question 1

What is considered to be the first evidence of differentiation in the cells of an embryo?

Accepted Answer

The occurrence of mRNAs for the production of tissue-specific proteins is considered the first evidence of differentiation in the cells of an embryo, as it indicates that certain cells are beginning to produce proteins specific to their future functions, marking the start of the process where cells start to take on distinct roles.

Question 2

If a Drosophila female has a homozygous mutation for a maternal effect gene,

Accepted Answer

A maternal effect gene affects the phenotype of the offspring through factors contributed by the mother, rather than directly by the genes of the offspring. If a Drosophila female has a homozygous mutation for a maternal effect gene, she will produce all mutant offspring, regardless of their genotype, because the gene product will be absent or nonfunctional in the mother's eggs. Therefore, all her offspring will show the mutant phenotype.

Question 3

Your brother has just purchased a new plastic model airplane. He places all the parts on the table in approximately the positions in which they will be located when the model is complete. His actions are analogous to which process in development?

Accepted Answer

Pattern formation is the process in development where cells acquire different identities based on their positions in the embryo, analogous to arranging model airplane parts on a table in their eventual positions. This process involves the spatial organization of tissues and organs, similar to how your brother is organizing the parts of the model airplane.

Question 4

The fact that plants can be cloned from somatic cells demonstrates that

Accepted Answer

The fact that plants can be cloned from somatic cells shows that differentiated cells retain all the genes of the zygote, indicating that the genetic information in cells is not lost during differentiation.

Question 5

Which of the following is true of embryonic stem cells but not of adult stem cells?

Accepted Answer

Embryonic stem cells are pluripotent, meaning they have the capacity to differentiate into all cell types in the organism. Adult stem cells, however, are multipotent and can only differentiate into a limited number of cell types.

Question 6

Let us suppose that someone is successful at producing induced pluripotent stem cells (iPS) for replacement of pancreatic insulin-producing cells for people with type 1 diabetes. Which of the following could still be problematic? I. the possibility that, once introduced into the patient, the iPS cells produce nonpancreatic cells
II) the failure of the iPS cells to take up residence in the pancreas
III) the inability of the iPS cells to respond to appropriate regulatory signals

Accepted Answer

All of the given scenarios could still be problematic even if induced pluripotent stem cells (iPS) are successful in replacing pancreatic insulin-producing cells for people with type 1 diabetes. There is a possibility that the introduced iPS cells may produce nonpancreatic cells which could lead to undesired effects in the recipient. Even if the iPS cells reach the pancreas, they may fail to take up residence or respond to appropriate regulatory signals which can hinder the desired outcome of the therapy. Hence, all the scenarios mentioned in the options could challenge the efficacy and safety of the iPS cell therapy for type 1 diabetes.

Question 7

Pax-6 is a gene that is involved in eye formation in many invertebrates, such as Drosophila. Pax-6 is found as well in vertebrates. A Pax-6 gene from a mouse can be expressed in a fly and the protein (PAX-6) leads to a compound fly eye. This information suggests which of the following?

Accepted Answer

The fact that a Pax-6 gene from a mouse can be expressed in a fly and lead to a compound fly eye suggests that Pax-6 is highly conserved and shows shared evolutionary ancestry across species. It does not necessarily suggest that the genes or proteins are identical in sequence or function, nor does it suggest that different PAX-6 proteins are responsible for different kinds of eyes. Additionally, the information in the passage does not provide evidence for whether a fly's Pax-6 gene can or cannot function in a mouse.

Question 8

A researcher is using adult stem cells and comparing them to other adult cells from the same tissue. Which of the following is a likely finding?

Accepted Answer

Adult stem cells have unique epigenetic modifications, including differential patterns of DNA methylation, that distinguish them from other adult cells in the same tissue. This allows them to differentiate into various cell types while maintaining their self-renewal potential. Therefore, it is likely that the cells from the two sources will exhibit different patterns of DNA methylation.

Question 9

In animals, what is the difference between reproductive cloning and therapeutic cloning?

Accepted Answer

The answer of In animals, what is the difference between...

Question 10

Mutations in which of the following genes lead to transformations in the identity of entire body parts?

Accepted Answer

Homeotic genes are responsible for determining the identity of different body segments and body parts during development. Mutations in these genes can result in the transformation of one body segment or part into another, leading to abnormal development.

Question 11

In 1997, Dolly the sheep was cloned. Which of the following processes was used?

Accepted Answer

Dolly the sheep was cloned through the process of nuclear transfer, in which the nucleus of an adult cell (in this case, a mammary gland cell) was fused with an enucleated egg cell and then implanted into a surrogate mother. This process is also known as somatic cell nuclear transfer (SCNT).

Question 12

Which of the following genes map out the basic subdivisions along the anterior-posterior axis of the Drosophila embryo?

Accepted Answer

Segmentation genes map out the basic subdivisions along the anterior-posterior axis of the Drosophila embryo, while homeotic genes determine the developmental fate of each segment. Egg-polarity genes provide the initial spatial cues for development, morphogens establish concentration gradients that determine cell fate, and inducers stimulate downstream gene expressions.

Question 13

In recent times, it has been shown that adult cells can be induced to become pluripotent stem cells (iPS). In order to make this conversion, what has been done to the adult cells?

Accepted Answer

To induce adult cells to become pluripotent stem cells (iPS), a retrovirus is used to introduce four specific regulatory genes. These genes are Oct4, Sox2, Klf4, and c-Myc.

Question 14

The bicoid gene product is normally localized to the anterior end of the embryo. If large amounts of the product were injected into the posterior end as well, which of the following would occur?

Accepted Answer

The bicoid gene product is a morphogen that specifies anterior structures in developing embryos, particularly in Drosophila (fruit flies). If it were injected into the posterior end, anterior structures would form at both ends of the embryo, leading to the development of anterior structures in both the normal anterior and the manipulated posterior sides.

Question 15

Reproductive cloning of human embryos is generally considered unethical. However, on the subject of therapeutic cloning there is a wider divergence of opinion. Which of the following is a likely explanation?

Accepted Answer

The wide divergence of opinion regarding therapeutic cloning likely stems from the potential medical benefits it could provide. Cloning to produce embryonic stem cells has the potential to lead to the development of personalized medical treatments and therapies for a wide range of diseases and conditions. While there are ethical concerns surrounding the creation and destruction of embryos, many argue that the potential benefits of therapeutic cloning outweigh these concerns.

Question 16

Which of the following is most closely identical to the formation of twins?

Accepted Answer

The answer of Which of the following is most closely...

Question 17

Embryonic lethal mutations result in

Accepted Answer

Embryonic lethal mutations result in phenotypes that never develop or are not viable, which means they die before being born or hatching.

Question 18

Which of the following problems with animal cloning might result in premature death of the clones?

Accepted Answer

Abnormal gene regulation due to variant methylation can result in premature death of clones as it can lead to various developmental abnormalities and diseases.

Question 19

The first cloned cat, called Carbon Copy, was a calico, but she looked significantly different from her female parent. Why?

Accepted Answer

X inactivation in the embryo is random and produces different patterns, which can explain why the cloned cat looked significantly different from its female parent despite having identical genetics.

Question 20

The product of the bicoid gene in Drosophila provides essential information about

Accepted Answer

The bicoid gene product in Drosophila provides important information about the anterior-posterior axis formation during embryonic development. Mutations in bicoid gene results in embryos with abnormalities in the anterior-posterior axis.

Quiz 16: Development, Stem Cells, and Cancer