Question 1

Which general genetic process is believed to account for the variety of cellular structures and functions in eukaryotic cells?

Accepted Answer

Variable gene activity, or differential gene expression, is the general genetic process believed to account for the variety of cellular structures and functions in eukaryotic cells. This process allows different genes to be turned on or off in different cells, leading to the development of specialized cell types and tissues. This is controlled by a variety of mechanisms, including transcription factors, epigenetic modifications, and signaling pathways, and is essential for normal development and function in multicellular organisms. The other choices (negative control exclusively, RNA processing, maternal environmental activities, and intron processing) do not explain the broad range of cellular structures and functions observed in eukaryotic cells.

Question 2

Which functions earlier in development: maternal- effect genes or zygotic genes?

Accepted Answer

maternal- effect genes

Question 3

Design an experiment that would allow you to determine if a particular nucleus in a Drosophila embryo is capable of directing development of an entire new fly.

Accepted Answer

Experiments in support of such genomic equivalence include the following: the observation that chromosome number and structure do not consistently change in different cells of an organism,nuclear transplantation in amphibians,and the presence of genes but no gene products in some tissues hemoglobin,for example).For the Drosophila experiment,one could do nuclear transplantation similar to the classic experiments in amphibians and recent experiments in mammals or transplant a cell from embryos of one genotype to the posterior end of the early embryos of another genotype.The transplanted cells would be reprogrammed into germ cells by the posterior P granules.The transplant can be detected in the next generation by the recognizable different phenotypes due to different genotypes of the donor and recipient.

Question 4

Provide a brief description of the variable gene activity hypothesis as it relates to development.What information is often provided in support of this hypothesis?

Accepted Answer

The answer of Provide a brief description of the variable...

Question 5

Describe the difference between a totipotent cell and a pluripotent cell.

Accepted Answer

The answer of Describe the difference between a totipotent cell...

Question 6

In what order do the segmentation genes function in Drosophilia?

Accepted Answer

The segmentation genes in Drosophila function in the order of gap genes, followed by pair-rule genes, and finally segment-polarity genes. This sequence is crucial for the proper segmentation of the Drosophila embryo.

Question 7

In Drosophila,which type of genes are controlled by maternal gene products laid down in gradients in the egg?

Accepted Answer

Maternal gene products laid down in gradients in the egg primarily control gap genes, which are involved in the early segmentation process of Drosophila development.

Question 8

Maternal effects are cases of extrachromosomal inheritance in which the genotype of the mother influences the phenotype of her immediate offspring in a non- Mendelian manner.Provide a rationale for the molecular basis of a maternal effect.

Accepted Answer

The answer of Maternal effects are cases of extrachromosomal inheritance...

Question 9

Three investigators-Nüsslein- Volhard,Wieschaus,and Lewis-won the Nobel Prize for physiology and medicine in 1995 for work they did in 1970 with Drosophila.Briefly describe their findings.

Accepted Answer

The answer of Three investigators-Nüsslein- Volhard,Wieschaus,and Lewis-won the Nobel Prize...

Question 10

Which of the following is a fundamental characteristic of the Notch pathway?

Accepted Answer

The Notch pathway is characterized by direct cell-to-cell contact, where the Notch receptor on one cell interacts with the Delta ligand on a neighboring cell, triggering a signaling cascade that influences cell fate determination and differentiation.

Question 11

In most species the expression of Hox genes is colinear with the anterior to posterior organization of the organism.Describe what this means.

Accepted Answer

The answer of In most species the expression of Hox...

Question 12

Provide an explanation of the differences between differentiation and determination.Provide examples of each process and indicate how each is involved in development.

Accepted Answer

The answer of Provide an explanation of the differences between...

Question 13

Arabidopsis thaliana has homologous gene clusters to the Hox genes found in Drosophila.What are these master regulatory clusters called?

Accepted Answer

The homologous gene clusters to the Hox genes found in Drosophila, present in Arabidopsis thaliana, are called MADS-box proteins. These are a family of transcription factors that play crucial roles in various aspects of plant development, including the regulation of flower development, similar to the role of Hox genes in animal development.

Question 14

It is often said that development is a two- step process.What two steps are likely to be referred to here?

Accepted Answer

The answer of It is often said that development is...

Question 15

Immediately after fertilization of a Drosophila egg,the zygote nucleus undergoes a series of divisions.Subsequent nuclear migration generates an_______.

Accepted Answer

After fertilization, the Drosophila egg undergoes rapid and synchronous cell divisions without cytokinesis, resulting in a multinucleate cytoplasmic mass called a syncytium. The zygote nucleus quickly undergoes several divisions, and the resulting nuclei migrate to the periphery of the egg, where they undergo further synchronous mitotic divisions to generate the syncytial blastoderm. Therefore, choice D (syncytium) is the best answer. Choices A (homeodomain), B (cleavage nucleus), C (zygote), and E (maternal effect) are not accurate descriptions of this process.

Question 16

How does determination relate temporally to differentiation?

Accepted Answer

The answer of How does determination relate temporally to differentiation?...

Question 17

Experiments involving nuclear transplantation in amphibians indicate that nuclei derived from blastula are more likely to support development of complete and normal adults compared with those derived from later stages of development.What do these experiments tell us about the process of development?

Accepted Answer

The answer of Experiments involving nuclear transplantation in amphibians indicate...

Question 18

Which term refers to the regulatory events that establish a specific pattern of gene activity and developmental fate for a given cell?

Accepted Answer

Determination refers to the regulatory events that establish a specific pattern of gene activity and developmental fate for a given cell. Differentiation refers to the process by which cells with the same genetic information become distinct from one another in terms of structure and function. Attenuation refers to the premature termination of transcription by RNA polymerase, often as a result of ribosomal stalling. Gradient regulation refers to the regulation of gene expression by the concentration gradient of a signaling molecule. Lysogeny refers to a state in which a viral genome is integrated into the host genome and is replicated along with it.

Question 19

What kinds of general observations cause one to conclude that development is the result of variable gene activity?

Accepted Answer

The answer of What kinds of general observations cause one...

Question 20

Mutations that eliminate a contiguous region in the Drosophila embryo's segmentation pattern are called_______ .

Accepted Answer

Gap genes are responsible for determining broad areas of the embryo's segmentation pattern. Mutations that eliminate a contiguous region in this pattern are known as gap mutations. Therefore, the correct answer is A) gap genes.

Quiz 23: Developmental Genetics