Multiple choice answers for Developmental Final

In the accompanying diagram, the protein marked #3 is a(n)

Repressor

Which of the following is a "show it" experiment?

In situ hybridization to examine spatial gene expression

In the accompanying diagram, the structure labeled “C” arises from which germ layer?

Mesoderm.

Where does the Spemann organizer form?

At the dorsal vegetal region

Which embryonic tissue gives rise to the nervous system?

Ectoderm

Which characteristic does not make an organism a good developmental model?

Ethical restrictions on embryo use

What would happen if Chordin is knocked out in the frog embryo?

Ventralization of embryo

Which signaling pathway is responsible for dorsal identity in frogs?

Wnt/β-catenin

Which of the following is not a function of the Spemann organizer?

Activate zygotic transcription

What is the defining feature of terminally differentiated cells?

Stable, specialized function

Which cells become the endoderm?

Cells in the vegetal pole

Which stage comes immediately after gastrulation?

Neurula

What is the role of transcription factors?

Bind promoters and regulate gene expression

The ______________ receives signals from the organizer to form neural tissue.

Ectoderm

Why is studying development in humans challenging?

Ethical and practical limitations restrict experimental manipulation

What do you predict is likely to happen if vegetal cytoplasm is transplanted to the animal pole?

Animal cells would adopt mesodermal fates

What is the function of the dorsal lip of the blastopore?

Organizer of embryonic body plan

What induces mesoderm formation in the marginal zone?

Nodal-related signals from vegetal cells

Which maternal determinant promotes endoderm fate?

VegT

Which protein is encoded by maternal VegT?

T-box transcription factor

Which cell type initiates the highest Nodal expression?

Nieuwkoop center cells

Which term describes the spatial arrangement of cells during development?

Morphogenesis

Which organism is best suited for large-scale mutagenesis screens in development?

Fly

What term defines the state when a cell will follow a fate even if it is moved?

Determined

Which statement best describes the concept of epigenesis?

Structures in the embryo arise progressively through interactions and differentiation

What did John Gurdon's nuclear transplant experiments in frogs demonstrate?

Differentiated nuclei retain full genetic potential

What does the occurrence of identical nonuplets suggest about the early human embryo?

Blastomeres from early cleavage divisions are totipotent

Which tissue originates from the mesoderm?

Muscle

____________ refers to the ability of a cell to respond to a signal.

Competence.

Which experiment led to the discovery of the organizer?

Spemann-Mangold transplantation

Which molecule is a BMP antagonist?

Chordin

Where is the frog blastocoel located?

Between vegetal and animal poles

Which best defines developmental potential?

All possible fates a cell can adopt

If you wanted to clone your pet dog, Daisy, you can do a somatic cell nuclear transplant experiment. For this, Daisy would have to be:

The somatic cell nucleus donor

Which of the following does not always apply to a maternal determinant?

It is uniformly distributed throughout the embryo

A triploblast is _

An animal with three germ layers

The endoderm gives rise to the

Gut

Which result would you expect if you applied an antagonist of the Wnt signaling pathway to an early 4-cell C. elegans embryo?

Both EMS daughters adopt an MS fate.

Which best describes planar cell polarity?

Coordinated orientation within the plane of a tissue

What would be the likely consequence of a mutation that disrupts spatial colinearity in a Hox gene cluster?

Homeotic transformations, where one segment develops characteristics of another

Which signaling pathway is centrally involved in establishing planar cell polarity in both Drosophila and vertebrates?

Non-canonical Wnt/Frizzled pathway

Embryos from a mother homozygous for a loss-of-function mutation in nanos will likely show defects in their:

Posterior structures

Engrailed is an example of a:

Segment polarity gene

The P4 cell in C. elegans is similar in function to which cell(s) in Drosophila?

Pole cells

What is the ploidy of the Arabidopsis endosperm?

Triploid

What is the fundamental difference in how the BMP signaling gradient is established along the D- V axis in frog versus fly embryos?

In frogs, BMP signaling is blocked dorsally by antagonists secreted from the organizer; in flies, a gradient of Dpp (BMP homolog) activity is shaped by localized production and modulation

How would a mutation in a gap gene like Kruppel affect the expression of pair-rule genes like even-skipped?

The striped pattern of even-skipped expression would be disrupted or altered in the region normally specified by Kruppel.

What is the main function of PIN proteins in Arabidopsis embryos?

Transport auxin directionally

In vertebrate development, failure of planar cell polarity signaling during gastrulation would primarily disrupt:

Anterior-posterior axis elongation

If two cell populations express different types of cadherins, what will likely happen?

They will selectively segregate

How does the Bicoid protein gradient affect the transcription of the hunchback gene?

It activates hunchback transcription at high concentrations

In vertebrates like frogs, the dorsal organizer is functionally similar to which Drosophila region?

Neuroectoderm

The primary body axes in an Arabidopsis seedling are:

Apical-Basal and Radial

What is a key similarity between frog and fly embryos in terms of signaling gradients and nervous system specification along the D-V axis?

Both use a BMP gradient, with low levels specifying neural tissue.

In frog embryos, what event marks the start of gastrulation?

Apical constriction of bottle cells

Radial intercalation results in:

Thinning and spreading of tissue

The APX-1 ligand in C. elegans interacts with which receptor to induce ABp fate?

GLP-1

BMPs (Bone Morphogenetic Proteins) are vertebrate signaling molecules involved in D-V patterning. What is the Drosophila homolog of BMPs in this context?

Decapentaplegic (Dpp)

How does the Dorsal morphogen gradient specify different cell fates along the D-V axis?

By activating or repressing different target genes at different threshold concentrations.

The diagram shows a synthetic transgene. If this transgene is introduced Drosophila, where would you expect to observe GFP expression in the embryo?

GFP would be expressed in an anterior-to-posterior gradient in the embryo

Which is the correct temporal order of Drosophila embryogenesis stages?

Syncytial blastoderm → Cellular blastoderm → Gastrulation → Segmentation

The post-translation modification of cactus protein that happens when Toll receptor is activated is:

Phosphorylation

What are the key similarities in Hox genes between flies and mice that highlight their conserved roles in development?

They are clustered on the chromosome and exhibit spatial colinearity with their expression domains.

The diagram shows the expression of a zygotic segmentation gene in Drosophila. Which class does it most likely belong to?

Pair-rule gene

A novel mutation in Drosophila prevents translational repression of maternal hunchback mRNA by Nanos. Predict the effect on the embryo:

Loss of posterior structures

How does the syncytial nature of the early Drosophila embryo facilitate the establishment of morphogen gradients?

It allows for free diffusion of molecules throughout the cytoplasm before cellularization

The diagram indicates how a hypothetical gene X is regulated by threshold concentrations of its regulatory transcription factors A and B. Factor A forms an anterior-to-posterior gradient (high anterior), and Factor B forms a posterior-to-anterior gradient (high posterior). Where would gene X be expressed?

Only in the extreme anterior region.

In Drosophila, a cactus mutant is expected to have:

Expanded ventral mesoderm

How does the timing of gene expression differ between maternal effect genes and zygotic genes and how does this relate to their roles in early development?

Maternal genes are expressed early and establish initial axes; zygotic genes are expressed later and refine these patterns.

Convergent extension relies primarily on which cellular behavior?

Coordinated medio-lateral intercalation of cells.

What cell lineage in C. elegans sets up the posterior fate?

P2

The diagram shows the enhancer regions of 5 different target genes. Which gene is most likely to be expressed in the zone where the concentration of the transcription activator is the lowest?

Target gene D

Which class of segmentation gene is first expressed after fertilization in Drosophila?

Gap

In Drosophila, pole cells are important because they:

Form the germline

A major difference between plant and animal development is that:

Plants do not undergo gastrulation

If a mutation in a maternal-effect gene results in all offspring of a homozygous mutant mother lacking terminal structures, what would you expect to observe in the offspring of a heterozygous mother? Assume the mutation is recessive.

None of the offspring will show the defect

Spatial colinearity in Hox gene clusters refers to the phenomenon where:

Hox genes at one end of the cluster are expressed at the anterior

On a fate map of a Drosophila embryo, the mesoderm is derived from cells located in the:

Ventral-most region