Biology II: Unit 1 Notes
The vertebrate ectoderm is the origin of the
nervous system
The _____ is(are) formed when the neural folds join and a portion of the neural plate sinks beneath the embryo's surface.
neural tube
The embryonic precursor to the human spinal cord is the _____. notochord mesoderm neural tube archenteron
neural tube
Part complete The bicoid gene is transcribed by _____.
nurse cells
If an amphibian zygote is manipulated so that the first cleavage plane fails to divide the gray crescent, then
only the daughter cell with the gray crescent will develop normally.
Among the following, the earliest consequence of the acrosomal reaction is _____.
the membrane of the egg depolarizing Fusion of the membranes of the egg and sperm causes membrane depolarization, known as the "fast" block to polyspermy, i.e., the prevention of additional sperm binding to the egg.
The plasma membrane of the sea urchin egg _____.
has receptor molecules that are specific for binding acrosomal proteins
Contact of a sea urchin egg with signal molecules on sperm causes the egg to undergo a brief _____. vitellogenesis acrosomal reaction mitosis membrane depolarization
membrane depolarization
In sea urchins, the "fast block" and the longer lasting "slow block" to polyspermy, respectively, are _____.
membrane depolarization and the cortical reaction
The pattern of embryonic development in which only the cells lacking yolk subsequently undergo cleavage is called _____.
meroblastic development, which is typical of birds
During gastrulation, invagination occurs at the _____.
During gastrulation, invagination occurs at the blastopore, which develops into the sea urchin's anus.
Which of the following is a result of gastrulation in animals? I) The archenteron is formed. II) The body axes are established. III) The germ layers are formed.
I, II, and III
What process produces the gradient of bicoid protein in a fertilized egg?
diffusion; Bicoid protein is produced at the anterior end and diffuses toward the posterior, resulting in a gradient.
During fertilization, the acrosomal contents _____.
digest the protective jelly coat on the surface of the egg
The archenteron of the developing sea urchin eventually develops into the _____.
digestive tract
Hans Spemann and colleagues developed the concept of the primary organizer in amphibian embryos while studying the
dorsal lip of the blastopore.
In humans, identical twins are possible because
early blastomeres can form a complete embryo if isolated.
The bicoid gene is a type of _____ gene.
egg-polarity Egg-polarity genes are responsible for establishing the polarity of the egg.
During the early development of a human embryo, the _____ eventually forms the _____. See Concept 47.2 (Page 1052)
epiblast ... ectodermal, mesodermal, and endodermal tissues The migration and differentiation of epiblast cells produce the embryo proper and its three basic tissues.
What structural adaptation in chickens allows them to lay their eggs in arid environments rather than in water?
extraembryonic membranes
In an egg cell treated with a chemical that binds calcium and magnesium ions, the _____.
fertilization envelope would not be formed
What triggers the translation of bicoid mRNA?
fertilization of the egg
Choose the correct developmental sequence of animal development.
fertilization → cleavage → gastrulation → organogenesis
Cadherins and other cell-adhesion molecules that guide cell migration are
glycoproteins
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.
In sea urchins, the process of fertilization produces a(n) _____.
Fertilization, the combination of haploid sets of chromosomes, results in the formation of a diploid zygote.
The embryos of all animals undergo gastrulation, a dramatic reorganization of cells critical to formation of the animal body. Do you understand all the terms associated with gastrulation? Drag the terms on the left to the appropriate blanks on the right to complete the sentences.
Following fertilization, the embryo undergoes cleavage to produce a ball of blastomeres called the blastula. Gastrulation is a process that includes a set of cells at or near the surface of the blastula moving to an interior location. Through formation of the archenteron, gastrulation reorganizes the blastula into a gastrula. This process establishes embryonic germ cell layers and forms a primitive digestive tube.
The migratory neural crest cells _____.
Form neural and non-neural structures in the periphery.
Gastrulation is the stage of embryonic development following cleavage. During gastrulation, cell division slows dramatically, and cells are rearranged in a precise way, forming three germ layers. The diagram below illustrates gastrulation in a frog embryo, represented in cross section. Drag the labels to their appropriate locations on the diagram. Use only pink labels for pink targets. Not all labels will be used.
Gastrulation is the process by which cells formed during cleavage are dramatically rearranged. By the end of gastrulation in a frog embryo, the gastrula has three embryonic germ layers, a primitive gut (archenteron), and a blastopore with a yolk plug. At this point, the major body axes are visible. For example, the blastopore will develop into the frog's anus, indicating the posterior end of the embryo. The events of gastrulation are largely affected by molecules called cytoplasmic determinants. Cytoplasmic determinants originate in the egg and are distributed in embryonic cells during cleavage. These molecules, which may be proteins or nucleic acids, help direct early development, including cell movements during gastrulation. Gastrulation begins with the appearance of the blastopore, which forms from an invagination of cells on the surface of the embryo. Cells roll inward through the blastopore and move to the interior of the embryo in a process called involution. Involution enables the formation of the endoderm and mesoderm. The primitive gut (archenteron) forms from endoderm. The blastocoel becomes smaller as the primitive gut expands. Once the three germ layers are established in the late gastrula, the next stage of embryonic development, organogenesis, can proceed.
Which of the following stages of development is defined by the three embryonic tissue layers (ectoderm, mesoderm, and endoderm)?
Gastrulation is the process that leads to the formation of the gastrula, which contains the three embryonic tissue layers.
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.
Which of the following statements about a gene that shows maternal effect inheritance is true?
Offspring will show a mutant phenotype if the mother has a mutant genotype. This statement is true; the gene is transcribed in the mother, and the mRNA is delivered to the zygote.
True or False? Pattern formation refers to events that organize embryonic cells in space
Pattern formation is the process by which the location of an embryo's body segments is determined.
Which of the following statements about pattern formation are true?
Positional information controls pattern formation. Differential gene expression affects the developmental process in animals. Homeotic genes code for transcription factors that control the development of segment-specific body parts. Cells receive molecular signals that communicate their position in relation to other cells. (Pattern formation is the development of a multicellular organism's spatial organization, including the arrangement of tissues and organs. Cells receive molecular signals, collectively called positional information, that inform the cells about their location in relation to other cells and to the body axes. Positional information regulates pattern formation. Homeotic genes are regulatory genes that work after the body axes have been established. Homeotic genes identify particular body segments in an individual, eventually leading to the formation of segment-specific body structures in the correct locations on the body.)
Cell signaling involves converting extracellular signals to specific responses inside the target cell. Different molecules are involved at each stage of the process. In this activity, you will sort items based on which stage they are involved in: reception, transduction, or response.
Receptor proteins (located in the plasma membrane or inside the cell) bind signaling molecules. The reception of the signal causes a shape change in the receptor molecule, to which other molecules inside the cell respond. The message is then relayed through signal transduction, which may involve a phosphorylation cascade or second messengers such as cAMP, Ca2+, or IP3. Possible responses to the signal may include synthesis of a particular protein or regulation of a particular enzyme.
In some rare salamander species, all individuals are females. Reproduction relies on those females having access to sperm from males of another species. However, the resulting embryos receive no genetic contribution from the males. Why do you think sperm are necessary for reproduction?
Sperm trigger egg activation.
Which of the following statements about the Bicoid protein is true? The Bicoid protein is a cytoplasmic determinant. The Bicoid protein is diffused evenly throughout the fertilized egg. The Bicoid protein establishes the dorsal-ventral body axis. The Bicoid protein is a regulatory transcription factor.
The Bicoid protein regulates expression of the embryo's early developmental genes.
The enlarged anterior portion of the neural tube will develop into a frog's _____.
The anterior end of the neural tube develops into the brain.
The _____ eventually develops into the sea urchin's digestive tract.
The archenteron, formed as a result of gastrulation, develops into the sea urchin's digestive tract.
Several hours after fertilization, cleavage results in the formation of a hollow ball of cells called a _____.
The blastula is a hollow ball of cells formed as the result of cleavage.
A researcher is using adult stem cells and comparing them to other adult cells from the same tissue. Which of the following findings is likely from this comparison?
The cells from the two sources exhibit different patterns of DNA methylation.
In vertebrates, the ectoderm gives rise to the _____.
The ectoderm gives rise to the outer layer of skin and the nervous system
An ectodermal thickening above the frog's notochord forms a _____.
The ectodermal thickening above the frog's notochord forms the neural plate.
Extraembryonic membranes develop in
mammals, birds, and lizards.
The primitive streak in a bird is the functional equivalent of _____.
the lip of the blastopore in the frog
The primitive streak in a bird is the functional equivalent of
the lip of the blastopore in the frog.
The archenteron develops into
the lumen of the digestive tract.
In recent times, it has been shown that adult cells can be induced to become pluripotent stem cells (iPS). To make this conversion, what has been done to the adult cells?
A retrovirus is used to introduce four specific master regulatory genes.
Histamine is a chemical substance released in inflammatory and allergic responses. The histamine H1 receptor on target cells is a G protein-coupled receptor that activates phospholipase C in response to the binding of histamine. Which statements are true about the binding of histamine to the histamine H1 receptor? Select all that apply.
A. Histamine binds extracellularly to the H1 receptor. B. When histamine binds to the H1 receptor, the receptor undergoes a conformation change and binds the inactive G protein. C.Once the G protein is active, it binds to the enzyme phospholipase C, activating it. D. Histamine is likely hydrophilic. When histamine encounters a target cell, it binds extracellularly to the H1 receptor, causing a change in the shape of the receptor. This change in shape allows the G protein to bind to the H1 receptor, causing a GTP molecule to displace a GDP molecule and activating the G protein. The active G protein dissociates from the H1 receptor and binds to the enzyme phospholipase C, activating it. The active phospholipase C triggers a cellular response. The G protein then functions as a GTPase and hydrolyzes the GTP to GDP. The G protein dissociates from the enzyme and is inactive again and ready for reuse.
Histamine is a chemical substance released in inflammatory and allergic responses. The histamine H1 receptor is a G protein-coupled receptor that activates phospholipase C in response to the binding of histamine. Complete the flowchart showing the process of histamine signal transduction from the H1 receptor. Drag the labels to their appropriate locations in the flowchart. Some labels will not be used.
After the reception of the histamine signaling molecule, the active G protein activates the enzyme phospholipase C. Phospholipase C cleaves PIP2 into DAG and IP3. IP3 diffuses through the cytosol and binds to an IP3-gated calcium channel in the ER membrane, causing it to open. As a result, Ca2+ ions flow out of the ER and into the cytosol. The increase in the calcium ion concentration in the cytosol helps activate the cellular response. Signal transduction pathways that involve phosphorylation cascades or multiple second messengers, such as histamine's signal transduction pathway, enable a signal to be amplified and regulated at different points. Similarly, multistep pathways can facilitate the coordination of cellular responses to multiple signals.
During gastrulation in frogs, cells from the animal pole spread over the embryo and form the _____.
Cells from the animal pole form the ectoderm.
As cleavage continues during frog development, the size of the blastomeres _____.
As cleavage continues during frog development, the size of the blastomeres _____. decreases as the number of the blastomeres increases
What are the cells created by cleavage called?
Blastomeres
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 statements provides a likely explanation?
Cloning to produce embryonic stem cells may lead to great medical benefits for many.
Cortisol is a steroid hormone that can pass through the plasma membrane. Complete the flowchart describing the interaction of cortisol with intracellular receptors. Drag the labels to their appropriate locations in the flowchart. Some labels will not be used.
Cortisol is a small, hydrophobic steroid hormone that can pass through the plasma membrane of cells. In target cells, cortisol binds to the intracellular receptor protein in the cytoplasm, forming a hormone-receptor complex. The hormone-receptor complex then moves into the nucleus and acts as a transcription factor, binding to specific genes and activating their transcription into mRNA. The mRNA that is produced is eventually translated into specific proteins. Proteins produced in response to the cortisol signal function in the stress response. For example, some of these proteins aid in elevating glucose levels in the blood, helping an animal to meet the demands of starvation or intense physical activity.
The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following statements to be true? A. The same codons in different organisms translate into different amino acids. B. Different organisms have different types of amino acids. C. DNA was the first genetic material. D. A gene from an organism can theoretically be expressed by any other organism.
D
Tissue and organ formation begins during the process of organogenesis. Which five of the following statements are true about organogenesis in a frog embryo?
During organogenesis, the three germ layers develop into rudimentary tissues and organs. The mesoderm gives rise to the notochord, which serves as a transient, organizing element for the developing embryo. Signaling molecules from the notochord help prompt development of the neural tube from foldings of the ectoderm. The neural tube eventually develops into the frog's central nervous system. Somites, which develop from the mesoderm, are blocks of tissue that form along both sides of the neural tube. Somite cells migrate to other locations in the embryo, where they give rise to a variety of tissues. The specific cell type that a somite cell develops into is partly determined by where in the somite the cell is located. The diagram below shows a close-up of one somite next to the neural tube. As you can see, cells located on the dorsal side of the somite are destined to become connective tissue in the skin, whereas cells located on the ventral side of the somite are destined to become bone.
Which of the following are the three germ layers contained in the gastrula?
Ectoderm, mesoderm, endoderm
Determine which terms, phrases, and images describe each phase of development.
Embryonic development proceeds through three stages. During cleavage, the cytoplasm of the zygote is divided into many different cells called blastomeres. By the end of cleavage, the embryo is called a blastula, which is a ball of cells surrounding a fluid-filled cavity called a blastocoel. During gastrulation, the embryo is called a gastrula. In this stage, cells undergo dramatic rearrangement, forming the embryonic germ layers and other structures, such as the blastopore. Once gastrulation is complete, the major body axes of the embryo (anterior-posterior and dorsal-ventral) are visible. During organogenesis, the three embryonic germ layers develop into the rudiments of organs. Structures such as the notochord, the neural tube, and somites form. Somite cells undergo differentiation, giving rise to different body tissues and organs, including the skeleton, muscles, and skin.
Which of the following statements correctly describes one of the main differences between embryonic stem cells and adult stem cells?
Embryonic stem cells can give rise to all cell types in the organism, and adult stem cells cannot.
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? View Available Hint(s)
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.
Life as we know it depends on the genetic code: a set of codons, each made up of three bases in a DNA sequence and corresponding mRNA sequence, that specifies which of the 20 amino acids will be added to the protein during translation. Imagine that a prokaryote-like organism has been discovered in the polar ice on Mars. Interestingly, these Martian organisms use the same DNA → RNA → protein system as life on Earth, except that there are only 2 bases (A and T) in the Martian DNA, and there are only 17 amino acids found in Martian proteins. Based on this information, what is the minimum size of a codon for these hypothetical Martian life-forms?
In the most general case of x bases and y bases per codon, the total number of possible codons is equal to xy . In the case of the hypothetical Martian life-forms, is the minimum codon length needed to specify 17 amino acids is 5 (25 = 32), with some redundancy (meaning that more than one codon could code for the same amino acid). For life on Earth, x = 4 and y = 3; thus the number of codons is 43, or 64. Because there are only 20 amino acids, there is a lot of redundancy in the code (there are several codons for each amino acid).
The notochord functions as a core around which mesodermal cells form the frog's _____.
In vertebrates, the notochord functions as a core around which mesodermal cells form the frog's backbone.
Which of these is true of the cytoplasm of an unfertilized egg? See Concept 18.4
It is an unevenly distributed mixture of mRNA, proteins, organelles, and other substances. Many proteins are found concentrated at one end of the cell or another and provide positional information to the developing embryo.
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.).
The three-layered embryo is the _____.
The gastrula, formed when the blastula undergoes gastrulation, is a ball of cells that consists of the three primary germ layers.
If bicoid mRNA is injected at the anterior end of an egg from a bicoid mutant mother, what would the phenotype of the resulting larva be?
The larva would be normal with one head at the anterior pole. The injected mRNA would rescue the mutant phenotype of the egg
As cleavage continues, a zygote forms into a solid multicellular ball called a(n) _____.
The morula is a solid ball of cells produced when the zygote undergoes cleavage.
The posterior portion of the neural tube will develop into the frog's _____.
The posterior portion of the neural tube develops into the spinal cord.
In animals, what is the difference between reproductive cloning and therapeutic cloning?
Therapeutic cloning supplies cells for repair of diseased or injured organs.
During gastrulation in frogs, a rod of mesoderm under the dorsal surface forms the _____.
This rod of mesoderm forms the notochord, a physically supportive structure.
The histamine H1 receptor is one of several existing histamine G protein-coupled receptors. Depending on many factors, including the type of receptor, histamine can trigger a variety of responses, including vasodilation, smooth muscle contraction, stimulation of gastric secretion, cardiac stimulation, and increased vascular permeability (causing runny nose and watery eyes). Which of the following could account for the different cellular responses to histamine? Select all that apply.
When histamine binds to a histamine receptor, the specific cellular response that results is determined by the following factors: the type of histamine receptor the type of cell in which the receptor is located the enzyme that is activated by the G protein associated with the receptor the types of second messengers involved in the signal transduction pathway the proteins activated by the second messengers Signaling molecules can trigger a multitude of cellular responses, which may ultimately affect the transcription of genes, the activity of proteins, or cell growth and division.
An embryo with meroblastic cleavage, extraembryonic membranes, and a primitive streak must be that of _____. a sea urchin an insect a bird an amphibian
a bird
The region of a Drosophila embryo with a low concentration of bicoid protein will develop into the _____.
abdomen
Which of the following is true of stem cells? They can reproduce indefinitely in culture. Their use is highly controversial. They can differentiate to produce many different kinds of specialized cells. They can be found in both embryonic and adult tissues. All of the above.
all of the above
Which of the following correctly matches the extraembryonic membrane with its function? amnion: waste disposal yolk sac: gas exchange chorion: nutrient storage allantois: waste storage
allantois: waste storage
Which of the following is not a body segment of the fruit fly embryo?
antennae
The first cavity formed during frog development is the _____.
blastocoel
At the time of implantation, the human embryo is called a _____. fetus gastrula blastocyst zygote
blastocyst
In which of the following organisms does holoblastic cleavage typically occur? I) sea urchins II) humans III) birds IV) fish
both I and II
Cell migration occurs extensively during ________. cleavage, but not during gastrulation or organogenesis gastrulation and cleavage organogenesis, but not during gastrulation or cleavage both gastrulation and organogenesis
both gastrulation and organogenesis
An embryonic cell that is "totipotent" is one that can ___
by itself, give rise to the entire embryo, as cleavage proceeds
The formation of the fertilization envelope requires an increase in the cytosolic concentration of ________.
calcium ions
Gases are exchanged in a mammalian embryo in the
chorion
Which of the following correctly displays the sequence of developmental milestones?
cleavage → blastula → gastrula
The term applied to a morphogenetic process whereby cells extend themselves, making the mass of the cells narrower and longer, is
convergent extension
The term applied to a morphogenetic process whereby cells extend themselves, making the mass of the cells narrower and wider, is ________. induction involution convergent extension invagination
convergent extension
The product of the bicoid gene in Drosophila could be considered a(n)
cytoplasmic determinant
Changes in the shape of a cell usually involve a reorganization of the
cytoskeleton
Changes in the shape of a cell usually involve a reorganization of the _____. extracellular matrix cytoskeleton nucleus transport proteins
cytoskeleton
In a newly fertilized egg, the vitelline layer _____.
ifts away from the egg and hardens to form a fertilization envelope
During frog development, the blastocoel ________. gives rise to the placenta is replaced by the expanding archenteron becomes the archenteron gives rise to the endoderm
is replaced by the expanding archenteron
In a frog embryo, the blastocoel is
located in the animal hemisphere.
If the apical ectodermal ridge is surgically removed from an embryo, it will lose
positional information for limb-bud pattern formation.
In a frog embryo, gastrulation _____.
proceeds by involution as cells roll over the lip of the blastopore
In an amphibian embryo, a band of cells called the neural crest
produces cells that migrate to form teeth, skull bones, and other structures in the embryo.
If cells from a carrot are removed and placed in a culture medium, they can develop into a normal adult plant. This demonstrates that carrot cells _____. See Concept 20.3
retain all the genes that were in the zygote that developed into the original plant AND are totipotent
The bicoid gene product is directly responsible for _____ in a developing Drosophila embryo.
the establishment of the anterior-posterior axis; The concentration gradient of bicoid protein determines the anterior-posterior axis of a developing Drosophila.
Bicoid mRNA is translated in _____.
the fertilized egg
The cortical reaction of sea urchin eggs functions directly in _____.
the formation of a fertilization envelope
What is the cortical reaction?
the formation of a fertilization envelope that bars additional sperm from entry into the egg
A codon consists of _____ bases and specifies which _____ will be inserted into the polypeptide chain. See Concept 17.1 (Page 339)
three ... amino acid
n 1997, Dolly the sheep was cloned. Which of the following processes was used? In 1997, Dolly the sheep was cloned. Which of the following processes was used? transfer of an adult cell's nucleus into an enucleated sheep egg, followed by incubation in a surrogate separation of an early stage sheep blastula into separate cells, one of which was incubated in a surrogate ewe replication and dedifferentiation of adult stem cells from sheep bone marrow isolation of stem cells from a lamb embryo and production of a zygote equivalent
transfer of an adult cell's nucleus into an enucleated sheep egg, followed by incubation in a surrogate
A high concentration of bicoid protein at the opposite ends of a developing Drosophila embryo would result in the development of a _____.
two headed fly; The head develops where there is a high concentration of bicoid protein.