In mammals, identical twins arise when an embryo formed from a single fertilized egg splits into two independent embryos, producing two genetically identical individuals. O For an early embryo to split into two embryos, both of which can develop into normal adults, the split must occur when embryonic cells are already differentiated. For an early embryo to split into two embryos, both of which can develop into normal adults, the split must

In mammals, identical twins arise when an embryo formed from a single fertilized egg splits into two independent embryos, producing two genetically identical individuals. O For an early embryo to split into two embryos, both of which can develop into normal adults, the split must occur when embryonic cells are already differentiated. For an early embryo to split into two embryos, both of which can develop into normal adults, the split must

Biology: The Dynamic Science (MindTap Course List)

4th Edition

ISBN:9781305389892

Author:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Publisher:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Chapter18: Dna Technologies: Making And Using Genetically Altered Organisms, And Other Applications

Section: Chapter Questions

Problem 8TYK

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A recently discovered bird species was found to have 29 chromosomes in its somatic cells before S phase. a. How many chromosomes (2n) are present in a somatic cell during mitosis? b. How many chromosomes does a bird receive from one parent? c. How many sister chromatids are present during metaphase 2? d. Assuming this species follows the same XX/XY sex differentiation as mammals, how many sex chromosomes are in an unfertilized egg?
Biologists have long been interested in the effects of radiation on cells. In one experiment, researchers examined the effect of radium on mitosis of chick embryo cells growing in culture. A population of experimental cells was examined under the microscope for the number of cells in telophase (as a measure of mitosis occurring) before, during, and after exposure to radium. The results are shown in the Figure. What is the effect of radium exposure on mitosis? Source: R. G. Canti and M. Donaldson. 1926. The effect of radium on mitosis in vitro. Proceedings of the Royal Society of London, Series B, Containing Papers of a Biological Character 100:413419.
In human spermatogenesis, mitosis of a stem cell gives rise to one cell that remains a stem cell and one cell that becomes a spermatogonium. (a) Draw four rounds of mitosis for a stem cell, and label the daughter cells. (b) For one spermatogonium, draw the cells it would produce from one round of mitosis followed by meiosis. Label the cells, and label mitosis and meiosis. (c) Explain what would happen if stem cells divided like spermatogonia.
A. In order to create an embryo from a somatic cell, the donor egg cell must have its ________________________ removed. B. Why is cloning extinct animals problematic?
researchers have been able to clonemammals by fusing a cell having a diploid nucleus (i.e., a somaticcell) with an egg that has had its nucleus removed.A. With regard to maternal effect genes, would the phenotype ofsuch a cloned animal be determined by the animal that donatedthe egg or by the animal that donated the somatic cell? Explain.B. Would the cloned animal inherit extranuclear traits from theanimal that donated the egg or from the animal that donated thesomatic cell? Explain.C. In what ways would you expect this cloned animal to be similarto or different from the animal that donated the somatic cell? Isit fair to call such an animal a clone of the animal that donatedthe diploid nucleus?
In recent years, techniques have been developed to clone mammals through a process called nuclear transfer, in which the nucleus of a somatic cell is transferred to an egg cell from which the nuclear material has been removed . Research has demonstrated that when a nucleus from a differentiated somatic cell is transferred to an eggcell, only a small percentage of the resulting embryos complete development, and many of those that do die shortly after birth. In contrast, when a nucleus from an undifferentiated embryonic stem cell is transferred to an egg cell, the percentage of embryos that complete development is significantly higher (W. M. Rideout, K. Eggan, and R. Jaenisch. 2001. Science 293:1095–1098). Propose a possible reason for why a higher percentage of cloned embryos develop successfully when the nucleus transferred comes from an undifferentiated embryonic stem cell.
a. Manually, using a pencil, draw a cell in anaphase II from an organism in which 2n = 2 and each chromosome is metacentric. b. Given that each G1 nucleus from this organism contains 16 picograms of DNA, how many picograms of chromosomal DNA would you expect in the cell shown here?
Mitotic nondisjunction can occur, particularly in tumor cells. Assume a single nondisjunction event involving the X chromosome occurs in a cell undergoing mitosis in a human female. First, consider the daughter cell with the smaller number of chromosomes: How many total chromosomes will this cell have? How many X chromosomes will this cell have? Next, consider the daughter cell with the larger number of chromosomes: How many total chromosomes will this cell have? How many X chromosomes will this cell have?
Scientists have retrieved separately fertilized nonidentical embryos of mice at the 64-cell stage and fused them together into one cell-cluster. Instead of developing into two mice, this develops into one mouse with many parents. Such animals from fused zygotes are called chimeras. Recently, a strange case occurred in a European hospital that revealed this could occur naturally in humans. A child with blood type AB was born to a mother with blood type O. Ruling out the possibility of a mixup in parents, the medical researchers examined the mother's parents and found many genetic markers that indicated that the type O mother who gave birth to the type AB child was actually a chimera from naturally fused embryos. One embryo gave rise to her bloodforming tissues and the other developed into her reproductive tissues. Briefly describe, the blood type of the child, the two tissue types existent in the mother, and indicate which contributed to the child, and the necessary blood types of the…
The size of one copy of the human genome is approximately 3 billion base pairs, and it contains about27,000 genes organized into 23 chromosomes.a. Human chromosomes vary in size. What wouldyou predict is the size of the average chromosome?b. Assuming that genes are spread evenly amongchromosomes, how many genes does an averagehuman chromosome contain?c. About half of the DNA in chromosomes containsgenes. How large (in base pairs) is an averagehuman gene?
Which of the following best describes the concept of cell differentiation during the development of a multicellular organism? A. During development, all of the genes in the embryo's cells are expressed at first, but fewer and fewer are expressed as time proceeds. B. During development, different sets of genes are deleted from different cell types so that at the end of development, each cell has only the genes it needs. C. During development, different cells become specialized to have different phenotypes even though they all originated from the same cell. ..
In the small intestine, stem cells in the crypts divide asymmetrically to maintain the population of cells that make up the villi; after each division, one daughter remains a stem cell and the other begins to divide rapidly to produce differentiated progeny.Explain why or why not.