Which of the following statements about pattern formation are true?
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b) Homeotic genes code for transcription factors that control the development of segment-specific body parts.
c) Cells receive molecular signals that communicate their position in relation to other cells.
e) Positional information controls pattern formation.
f) Differential gene expression affects the developmental process in animals.
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.
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Classify each phrase or term as applying to fly A only, fly B only, or both fly A and fly B. The term "Hox genes" applies to clusters of homeotic genes found in many different animals, including fruit flies. After segmentation genes have established the body segments, Hox genes trigger the development of segment-specific body structures in the correct locations.
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Fly A ONLY: "wild type," "possesses normal Hox genes," "exhibits normal pattern formation"
Fly B ONLY: "exhibits abnormal pattern formation," "homeotic mutant," "possesses mutant Hox genes'
Both Fly A and Fly B: "produces transcription factors triggering gene expression for segment-specific structures"
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A high concentration of bicoid protein at the opposite ends of a developing Drosophila embryo would result in the development of a _____.
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two-headed fly
The head develops where there is a high concentration of bicoid protein.
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The bicoid gene product is directly responsible for _____ in a developing Drosophila embryo.
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the establishment of the anterior-posterior axis
The concentration gradient of bicoid protein determines the anterior-posterior axis of a developing Drosophila.
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The region of a Drosophila embryo with the highest concentration of bicoid protein will develop into the _____.
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Head
The head develops where there is a high concentration of bicoid protein.
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What triggers the translation of bicoid mRNA?
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fertilization of the egg
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The bicoid gene is a type of _____ gene.
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Egg-polarity
Egg-polarity genes are responsible for establishing the polarity of the egg.
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The region of a Drosophila embryo with a low concentration of bicoid protein will develop into the _____.
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abdomen
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What process produces the gradient of bicoid protein in a fertilized egg?
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diffusion
Bicoid protein is produced at the anterior end and diffuses toward the posterior, resulting in a gradient.
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Bicoid mRNA is translated in _____.
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the fertilized egg
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Which of these regions is most likely to develop into the Drosophilia's head?
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This is the region with the highest concentration of bicoid protein
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The bicoid gene is transcribed by _____.
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nurse cells
Nurse cells transcribe the bicoid gene.
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Which of the following is not a body segment of the fruit fly embryo?
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Antenna
The antenna is not a body segment of a fruit fly embryo.
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Which of the following statements about a gene that shows maternal effect inheritance is true?
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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.
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True or False? Pattern formation refers to events that organize embryonic cells in space
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True
Pattern formation is the process by which the location of an embryo's body segments is determined.
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Where is bicoid mRNA translated?
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Fertilized egg
bicoid mRNA is translated at the anterior pole of the fertilized egg.
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Which body part develops in regions with a low concentration of Bicoid protein?
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Abdomen
The regions with low concentrations of Bicoid protein develop into posterior structures such as the abdomen.
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Which of the following statements about the Bicoid protein is true?
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The Bicoid protein is a regulatory transcription factor.
The Bicoid protein regulates expression of the embryo's early developmental genes.
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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?
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The larva would be normal with one head at the anterior pole.
The injected mRNA would rescue the mutant phenotype of the egg.
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An embryo with meroblastic cleavage, extra-embryonic membranes, and a primitive streak must be that of
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a bird.
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The archenteron of the developing frog eventually develops into the
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digestive tract.
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The vertebrate ectoderm is the origin of the
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nervous system.
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A correct statement is:
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The mesoderm gives rise to the notochord.
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In a study of the development of frog embryos, several early gastrulas were stained with vital dyes. The locations of the dyes after gastrulation were noted. The results are shown in the following table.
The endoderm was probably stained with
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green and purple colors.
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The primitive streak in a bird is the functional equivalent of
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the lip of the blastopore in the frog.
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Extraembryonic membranes develop in
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mammals, birds, and lizards.
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Gases are exchanged in a mammalian embryo in the
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chorion.
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In a frog embryo, the blastocoel is
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located in the animal hemisphere.
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In an amphibian embryo, a band of cells called the neural crest
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produces cells that migrate to form teeth, skull bones, and other structures in the embryo.
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If the apical ectodermal ridge is surgically removed from an embryo, it will lose
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positional information for limb-bud pattern formation.
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Hans Spemann and colleagues developed the concept of the primary organizer in amphibian embryos while studying the
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dorsal lip of the blastopore.
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If an amphibian zygote is manipulated so that the first cleavage plane fails to divide the gray crescent, then
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only the daughter cell with the gray crescent will develop normally
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Cadherins and other cell-adhesion molecules that guide cell migration are
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glycoproteins.
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The term applied to a morphogenetic process whereby cells extend themselves, making the mass of the cells narrower and longer, is
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convergent extension.
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Changes in the shape of a cell usually involve a reorganization of the
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cytoskeleton.
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The product of the bicoid gene in Drosophila could be considered a(n)
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cytoplasmic determinant.
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The product of the bicoid gene in Drosophila provides essential information about
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the anterior-posterior axis.
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The fact that plants can be cloned from somatic cells demonstrates that
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differentiated cells retain all the genes of the zygote
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