Biology Exam 4 Notecards (Chapter 20)

TRUE

Following implantation, the multiplying cells of the human embryo reorganize to form a gastrula which contains the three primary germ layers:

FALSE

Gap genes are sold in the most fashionable malls in America:

Progenitor

A model organism called Caenorhabditis elegans (a soil nematode) has been used to study cell signaling during development because of its simplicity. For example, a structure such as the vulva arises from only three cells, which are called ________________ cells:

Loss-of-function

A mutation in a gene that results in an inactive protein product is known as a ___________________ mutation:

Gain-of-function

A mutation in a gene that results in it being expressed in the wrong place or at the wrong time is known as a _____________________ mutation:

TRUE

A researcher has discovered a new mutant strain of mice where individuals develop two extra eyes—one on each ear. Given the appearance of "extra" eyes, these mice likely carry a gain-of-function mutation in Pax6 (or in a gene acting downstream of Pax6):

Ligand

A signaling molecule that binds a membrane protein is called a __________:

TRUE

An example of gene regulation at the level of translation is the ability of the Bicoid protein to repress translation of caudal mRNA and for Nanos protein to repress translation of hunchback mRNA:

Clone

An individual that carries an exact copy of the nuclear genome of another individual following a successful nuclear transfer is called a __________:

TRUE

As cells continue differentiating, they increasingly lose their developmental potential and their fate becomes more restricted:

TRUE

Combinatorial control is a general principle for the regulation of gene transcription and is observed in many stages of development in all multicellular organisms:

TRUE

Development proceeds such that each successive group of genes that are expressed refine and narrow the pattern of differentiation generated by previous groups:

FALSE

Differentiating cells delete the DNA for genes they do not need:

TRUE

Early development in Drosophila includes nuclear division, but not cell division. This gives rise to a single cell with many nuclei:

EGF and Notch ligands are unique to nematodes and only found in Caenorhabditis elegans

Epidermal growth factor (EGF) secreted from an anchor cell binds to its receptor on a nearby cell and initiates signal transduction. Which statement describing this signaling pathway is not correct?

Transduction

Extracellular molecules activating membrane proteins that in turn activate molecules inside the cell that control differentiation is an example of signal __________:

TRUE

Homeotic genes encode very important transcription factors that specify the identity of body parts or segments during development. For example, the development of legs on thoracic segments T1, T2, and T3 and wings on segment T2 is controlled by homeotic genes:

FALSE

Human development begins with fertilization, but the fertilized egg does not begin to divide until after it implants in the uterine wall:

-Bone development in the human embryo -Heart development in the human embryo -Nervous system development in the human embryo -Pancreas development in the human embryo

Imagine that a human embryo carries a mutation in the gene encoding the Notch receptor. What will this mutation affect?

The mouse may go on to form an ectopic eye that resembles a mouse eye in shape and structure, given that the genes acting downstream of Pax6 are still "mouse" genes

Imagine that a scientist introduced a copy of the human Pax6 gene into a mouse. What would likely happen in this scenario?

Anchor

In Caenorhabditis elegans vulval development, the fate of the progenitor cells is dependent on their proximity to the ___________ cell, which secretes epidermal growth factor:

FALSE

In a normal Drosophila embryo, a gap gene called Krüppel is expressed in the anterior end because it is activated by Hunchback protein, and this region contains a high level of Hunchback:

Inner cell mass

In human development, cell rearrangement within the ball of cells (morula) leads to a hollow sphere with a "mound" of cells at one pole. This group of cells is called the:

TRUE

In human development, early divisions of the embryo are contained within the egg's outer membrane and thus upon each division, egg cytoplasm is partitioned into smaller and smaller cells which form the morula:

TRUE

In human development, the blastocyst, which is a hollow sphere of developing cells, implants in the uterine wall approximately 5 to 6 days after fertilization:

TRUE

In the Drosophila embryo, gap genes govern the partitioning of the anterior-posterior gradient into segments:

Lateral

In vulval development in Caenorhabditis elegans, the progenitor cell nearest to the anchor cell is exposed to the highest concentration of epidermal growth factor and activation of its EGF receptor promotes type I cell differentiation. The type 1 cell then prevents type 1 differentiation in adjacent progenitor cells, a mechanism called _________________ inhibition:

TRUE

Molecules that are similar in sequence among distantly related organisms, such as many transcription factors important in development, are said to be evolutionarily conserved:

TRUE

Mutants of Drosophila melanogaster have been used extensively to explore the genetic control of early development, particularly the hierarchical control of development, which means that genes expressed at each stage control the expression of genes that act later:

FALSE

Mutations in the plant Arabidopsis were used to detect the influence of multiple genes on its phenotype:

TRUE

Mutations in the plant Arabidopsis were used to detect the influence of multiple genes on its phenotype:

TRUE

Pax6 is a transcription factor that can act as a repressor for some of its target genes or as an activator for others:

TRUE

Sox9 and Sox10are both transcription factors involved in the later stages of the development of the peripheral nervous system. The expression of Sox9 and Sox10 is regulated by the products of another set of genes—Pax3 and Pax7. This interaction between Sox9, Sox10, Pax3, and Pax7 is an example of combinatorial control:

TRUE

The Nobel Prize for Physiology or Medicine was awarded to Christiane Nusslein-Volhard and Eric F. Wieschaus due to their discovery that Drosophila development begins in the maturing oocyte, before fertilization:

TRUE

The Pax6 gene is evolutionarily conserved between fruit flies, mice, and humans. This gene has a similar sequence in all of these organisms, and performs a similar role in eye development (although the eyes of fruit flies and mammals are very different in structure):

Zygote

The fertilized egg is also called the __________:

FALSE

The fertilized egg is totipotent, whereas the cells from the inner cell mass, called embryonic stem cells, are pluripotent. Only the embryonic stem cells can give rise to the entire organism:

It can give rise to a complete organism

The fertilized egg is totipotent, which means:

Receptor

The membrane protein that is bound by a chemical signal is called the __________:

TRUE

The question of whether animal eyes have evolved independently in different organisms or have evolved once from a single organism and then diverged over time is still being actively investigated by evolutionary scientists:

FALSE

The rate of transcription for any one gene in any given cell type is determined by only one transcription factor:

TRUE

To avoid using controversial embryonic stem cells, scientists have learned to reprogram fully differentiated adult cells and return them to a pluripotent state:

Cis-regulatory

Transcription factors like Pax6 interact with their target genes by binding short sequences adjacent to the 5' end of a gene sequence called _________________ elements:

TRUE

When pair-rule genes and segment-polarity genes are mutated, larvae display disturbances in segmentation patterns:

Planarians

Which of the following organisms possess simple eye "pits," which although not morphologically similar to mammalian eyes, they are still capable of sensing light?

Cells become differentiated because genes that are not being expressed are deleted

Which of the following statements about differentiated cells is not correct? -Cells become differentiated because genes that are not being expressed are deleted -Transfer of a nucleus from a fully differentiated cell into an unfertilized egg with no nucleus can support the development of an entire organism -Cells become differentiated because of changes in nuclear gene expression -Mammals have been cloned from completely differentiated cells -Differentiated cells contain a complete genome

The caudal and hunchback mRNAs are transcribed in the egg and then transported back to regulate the mother's genome

Which of the following statements about maternal-effect genes is not correct? -Maternal-effect genes are expressed by the mother but affect the phenotype of the offspring -The composition of RNA and proteins in an oocyte is not uniform across the cell -Bicoid and nanos mRNA and protein in Drosophila oocytes are localized either in the anterior (bicoid) or posterior (nanos) of the egg -The anterior-posterior axis set up by gradients of Bicoid and Nanos proteins is reinforced by gradients of two transcription regulators called Caudal and Hunchback -The caudal and hunchback mRNAs are transcribed in the egg and then transported back to regulate the mother's genome

-C. elegans are a type of nematode -C. elegans are generally hermaphrodites -The generation time of C. elegans is under three days -C. elegans are small in size, allowing for their easy culture in the lab

Which of the following statements are true regarding C. elegans?

-Different cell whorls in this plant give rise to distinct structures, such as carpels or stamens -The combinatorial control of transcription by AP2, AP3, PI, and AG in Arabidopsis leads to the development of different plant structures -Four different cell whorls are located within the floral meristem of an Arabidopsis plant

Which of the following statements is true regarding Arabidopsis? CArabidopsis is also referred to as "mouse-ear cress.":

The linear order of Hoxgenes along the chromosome, the anterior-posterior orientation of the embryo, and timing of expression for the genes in Hoxclusters is observed only in Drosophila

Which one of the following statements about homeotic, or Hox, genes is not correct?

Pax6 protein is so central to eye development that after transferring the mouse Pax6 to the fruit fly, the fly produced eyes similar to that of a mouse

Which one of the following statements does not support the argument against multiple independent origins of eyes?

Genetic programs evolve, whereas computer programs do not

Which one of the following statements points out a significant limitation to the analogy between genetic programs and computer programs?

The percentage of living animals possessing true eyes that can produce an image is small

Which statement about diversity in eye development is not correct? -Evolution of the spherical lens improved images as animals evolved -Both squids and vertebrates have single-lens eyes, but they are very different in their development, anatomy, and physiology -Planaria have the simplest eyes, which are basically pit-shaped cells containing photoreceptors -Compound eyes consist of hundreds of small lenses arranged on a convex surface -The percentage of living animals possessing true eyes that can produce an image is small

The percentage of living animals possessing true eyes that can produce an image is small

Which statement about diversity in eye development is not correct? -Planaria have the simplest eyes, which are basically pit-shaped cells containing photoreceptors -Both squids and vertebrates have single-lens eyes, but they are very different in their development, anatomy, and physiology -Compound eyes consist of hundreds of small lenses arranged on a convex surface -The percentage of living animals possessing true eyes that can produce an image is small -Evolution of the spherical lens improved images as animals evolved

Ectoderm gives rise to cells lining the digestive tract and lungs, as well as liver and pancreas

Which statement about the differentiation of the three primary germ layers is not correct? -Ectoderm gives rise to cells lining the digestive tract and lungs, as well as liver and pancreas -Ectoderm gives rise to epithelial cells, pigment cells of skin, and nerve cells in the brain -Germ layers are sheets of cells that will differentiate into specialized cells -Mesoderm gives rise to cells that make up the inner layer of skin, muscle cells, and red blood cells -Endoderm gives rise to cells lining the digestive tract and lungs, as well as liver and pancreas