Muscle cells and nerve cells in one species of animal owe their differences in structure to
having different genes expressed.
Differentiation of cells is not easily reversible because it involves
chemical modifications of histones and DNA methylation.
In animals, embryonic stem cells differ from adult stem cells in that
embryonic stem cells are totipotent, and adult stem cells are pluripotent.
The general process that leads to the differentiation of cells is called
In 1997, Dolly the sheep was cloned. Which of the following processes was used?
fusion of an adult cell's nucleus with an enucleated sheep egg, followed by incubation in a surrogate
In sea urchins, the process of fertilization produces a(n) _____.
zygote (Fertilization, the combination of haploid sets of chromosomes, results in the formation of a diploid zygote.)
What is the cortical reaction?
the formation of a fertilization envelope that bars additional sperm from entry into the egg
As cleavage continues, a zygote forms into a solid multicellular ball called a(n) _____.
morula (The morula is a solid ball of cells produced when the zygote undergoes cleavage.)
Several hours after fertilization, cleavage results in the formation of a hollow ball of cells called a _____.
blastula (The blastula is a hollow ball of cells formed as the result of cleavage.)
The three-layered embryo is the _____.
gastrula (The gastrula, formed when the blastula undergoes gastrulation, is a ball of cells that consists of the three primary germ layers.)
The _____ eventually develops into the sea urchin's digestive tract.
archenteron (The archenteron, formed as a result of gastrulation, develops into the sea urchin's digestive tract.)
During gastrulation, invagination occurs at the _____.
blastopore (During gastrulation, invagination occurs at the blastopore, which develops into the sea urchin's anus.)
In vertebrates, the ectoderm gives rise to the _____.
outer layer of skin (The ectoderm gives rise to the outer layer of skin and the nervous system)
In animal development, which of the following best describes the process of cleavage?
Mitosis (Cleavage refers to the rapid cell division that takes place in animals after fertilization. Cleavage partitions the egg cytoplasm without additional cell growth taking place.)
What are the cells created by cleavage called?
Blastomeres (A blastomere is a cell created by cleavage division.)
Which of the following are the three germ layers contained in the gastrula?
Ectoderm, mesoderm, endoderm (These are the three basic embryonic cell layers of all vertebrate embryos.)
Which of the following stages of development is defined by the three embryonic tissue layers (ectoderm, mesoderm, and endoderm)?
Gastrula (Gastrulation is the process that leads to the formation of the gastrula, which contains the three embryonic tissue layers.)
What happens to a cell during the process of differentiation?
It undergoes a change toward a more specialized form or function. (During organogenesis, embryonic cells become progressively more specialized as they develop into their specific cell type (brain, muscle, etc.).)
A child is born without a fully developed pancreas. He is normal in all other respects, and thus doctors believe that the problem most likely began early in development. During which of the following processes did the original error most likely occur?
Endoderm formation (The endoderm provides the cells that develop into the lining of the digestive and respiratory tracts, as well as the liver and pancreas. Problems with its formation could result in an unformed pancreas.)
True or false? Early animal development progresses through distinct stages: first the production of the zygote through fertilization, then cleavage, then the formation of the gastrula, and then the formation of the blastula.
False (The formation of a gastrula is the last stage in early animal development the zygote undergoes cleavage to form a blastula, which eventually forms a gastrula.)
You buy a pie that contains a swirled mixture of chocolate and vanilla filling. When you cut the pie up, you notice that some slices have more chocolate than vanilla and that other slices have more vanilla than chocolate. This uneven distribution of chocolate and vanilla is most like the uneven distribution of
cytoplasmic determinants in a zygote.
As an embryo develops, new cells are produced as the result of
Contact of a sperm with signal molecules in the coat of an egg causes the sperm to undergo
the acrosomal reaction.
Contact of an egg with signal molecules on sperm causes the egg to undergo a brief
The vitelline layer of the sea urchin egg
has receptor molecules that are specific for binding acrosomal proteins.
From earliest to latest, the overall sequence of early development proceeds as follows:
acrosomal reaction -> cortical reaction -> synthesis of embryo's DNA begins -> first cell division
The cortical reaction functions directly in the
formation of a fertilization envelope.
The "slow block" to polyspermy is due to
formation of the fertilization envelope.
As cleavage continues during frog development, the size of the blastomeres
decreases as the number of the blastomeres increases.
The sequence of developmental milestones proceeds as follows: