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Download Developmental Biology MCQs Free PDF

Developmental Biology MCQ Quiz - Objective Question with Answer for Developmental Biology - Download Free PDF

Last updated on Jun 18, 2025

Latest Developmental Biology MCQ Objective Questions

Developmental Biology Question 1:

The figure below shows the genes (a, b, c, d, f, I, m, n) that are expressed in cell types 1, 2, and 3 because of the concentration of morphogen signaling received by these cells.

qImage682de4be1ea4c56529f3be88

Which one of the following statements is correct about the pattern of gene expression induced by the morphogen?

The transcription factor activated by the morphogen has:

  1. higher affinity for regulatory region of a than that of d. 
  2. higher affinity for regulatory region of f than that of c. 
  3. same affinity for regulatory regions of a and b.
  4. lower affinity for regulatory region of m than that of c.

Answer (Detailed Solution Below)

Option 2 : higher affinity for regulatory region of f than that of c. 

Developmental Biology Question 1 Detailed Solution

The correct answer is Option 2: Higher affinity for regulatory region of f than that of c

Concept:

  • Gene expression in different cell types is regulated by morphogen concentration gradients. Morphogens are signaling molecules that determine cell fate based on their local concentrations.
  • The transcription factor activated by the morphogen binds to the regulatory regions of specific genes to activate or repress their expression.
  • The affinity of the transcription factor for the regulatory regions of various genes determines which genes are expressed in response to varying morphogen concentrations.
    • High affinity: The transcription factor can bind and activate gene expression even at low concentrations.
    • Low affinity: The transcription factor requires a high concentration to bind effectively and activate gene expression.

Explanation:

  • The transcription factor activated by the morphogen has higher affinity for the regulatory region of gene f than that of gene c. This means gene f is expressed at lower morphogen concentrations compared to gene c. The spatial pattern of gene expression is determined by this differential affinity, ensuring that specific genes are activated in different cell types based on morphogen concentration.
  • The higher affinity for f's regulatory region implies that f is expressed earlier (or in cells exposed to lower morphogen concentrations) than c, which requires higher morphogen levels for activation.

Other Options:

  • Higher affinity for regulatory region of a than that of d. This is incorrect because 'a' requires higher morphogen (and thus more activated transcription factor) to be expressed than 'd', the transcription factor must have a lower affinity for 'a's regulatory region compared to 'd's.
  • Same affinity for regulatory regions of a and b. This is incorrect as morphogen signaling typically induces differential gene expression, meaning the transcription factor does not have identical affinity for two distinct genes.
  • Lower affinity for regulatory region of m than that of c. This is incorrect because Gene 'm' is expressed in Cell Types 1, 2, and 3 (all morphogen levels). Gene 'c' is expressed only in Cell Type 1 (highest morphogen). Since 'm' is expressed at lower morphogen levels, the transcription factor has a higher affinity for 'm's regulatory region. Since 'c' requires the highest morphogen level, the transcription factor has a lower affinity for 'c's regulatory region.

Developmental Biology Question 2:

The presence of E-cadherin activates the Hippo pathway in the inner cell mass (ICM). Experimentally eliminating E-cadherin disrupts both apicobasal polarity and specification of the ICM and trophoectoderm lineages. Which one of the following schemes leads to pluripotency?

  1. qImage682ddc9f5f30b6a9b3ab0bad
  2. qImage682ddc9f5f30b6a9b3ab0bb0
  3. qImage682ddc9f5f30b6a9b3ab0bb3
  4. qImage682ddca05f30b6a9b3ab0bb6

Answer (Detailed Solution Below)

Option 1 : qImage682ddc9f5f30b6a9b3ab0bad

Developmental Biology Question 2 Detailed Solution

The correct answer is Option 1

Concept:

  • E-cadherin is a cell adhesion molecule crucial for maintaining tissue architecture and cell polarity during early embryonic development.
  • The Hippo pathway is a signaling pathway that regulates organ size by controlling cell proliferation and apoptosis. In embryonic development, it plays a key role in the specification of cell lineages and pluripotency.
  • Apicobasal polarity refers to the spatial orientation of cellular components, which is essential for proper tissue organization and development of the inner cell mass (ICM) and trophoectoderm lineages.

Hippo Pathway:

  • In mammals, the core kinases are MST1/2 (mammalian Ste20-like protein kinases 1 and 2) and LATS1/2 (large tumor suppressor kinases 1 and 2).
  • YAP (Yes-associated protein) and TAZ (transcriptional coactivator with PDZ-binding motif) are key transcriptional coactivators regulated by the Hippo pathway.
    • Hippo Pathway Activation: When the Hippo pathway is active (meaning the kinases MST1/2 and LATS1/2 are active), they phosphorylate YAP/TAZ. Phosphorylated YAP/TAZ are either retained in the cytoplasm (prevented from entering the nucleus) or degraded. This leads to reduced YAP/TAZ activity in the nucleus.
    • Hippo Pathway Inactivation: When the Hippo pathway is inactive (meaning MST1/2 and LATS1/2 are inactive), YAP/TAZ are not phosphorylated. Unphosphorylated YAP/TAZ can then translocate to the nucleus, where they bind to transcription factors (like TEAD) to regulate gene expression. This leads to active YAP/TAZ in the nucleus.
  • The ability of a cell to differentiate into all cell types of the three germ layers (ectoderm, mesoderm, and endoderm) but not extra-embryonic tissues. Key pluripotency factors include Oct4, Sox2, and Nanog. High levels of Oct4 are associated with pluripotency in the Inner Cell Mass (ICM)

 

Developmental Biology Question 3:

The table below shows the outcomes of surgical experiments in chick embryos.

Surgical experiments

Outcomes

A.

Early wing bud progress zone is transplanted to a late wing bud after the formation of zeugopod

An extra set of ulna and radius is formed

B.

An extra ZPA is transplanted to anterior limb bud mesoderm after the formation of stylopod

Pattern duplication of ulna, radius and digits occurs

C.

Late wing bud progress zone, after the formation of zeugopod, is transplanted to an early wing bud that has just formed stylopod

Formation of autopod will be affected

D.

Early leg mesenchyma is transplanted just beneath the wing AER after the formation of stylopod

Distal leg structures develop at the end of the wing


Which one of the following options represents a combination of all correct outcomes?

  1. A and B
  2. B and D
  3. A and C
  4. A and D

Answer (Detailed Solution Below)

Option 4 : A and D

Developmental Biology Question 3 Detailed Solution

The correct answer is A and D

Explanation:

Limb development in vertebrates, including chick embryos, is controlled by complex signaling interactions between different limb bud regions. Key components involved include:

  • Progress Zone (PZ): A mesodermal region beneath the apical ectodermal ridge (AER) essential for proximodistal limb development.
  • Zone of Polarizing Activity (ZPA): A posterior mesodermal region that governs anteroposterior patterning via Sonic Hedgehog (Shh) signaling.
  • Apical Ectodermal Ridge (AER): A signaling center for limb outgrowth.
  • Zeugopod: The intermediate segment of the limb (ulna and radius).
  • Stylopod: The proximal limb segment (humerus/femur).

Option A: The Early wing bud progress zone is transplanted to a late wing bud after the formation of the zeugopod.

  • When the early progress zone is transplanted to a late wing bud, it retains its developmental programming and induces the formation of an extra set of ulna and radius (zeugopod structures).
  • This outcome is correct as the transplanted progress zone is programmed for zeugopod formation, even though the host tissue is at a later stage.

Option B: An extra ZPA is transplanted to anterior limb bud mesoderm after the formation of the stylopod.

  • Once the stylopod has formed, the tissue's response to ZPA signals diminishes. ZPA-induced pattern duplication primarily affects digits, not the entire limb segments like ulna and radius at late stages.

Option C: Late wing bud progress zone, after the formation of zeugopod, is transplanted to an early wing bud that has just formed stylopod.

  •  A late PZ is already committed to distal fates (autopod). Transplanting it into an early environment does not affect the autopod per se, but instead fails to support the full proximodistal outgrowth. It will not properly induce formation of earlier segments.

Option D: Early leg mesenchyme is transplanted just beneath the wing AER after the formation of stylopod.

  •  The AER provides signals (e.g., FGF) that promote distal development. Early mesenchyme retains plasticity and can respond to AER signaling to form distal structures even when placed in wing environment.

Developmental Biology Question 4:

If planaria is cut in transverse, active Wnt signaling in the posterior side of the head piece is essential for the regeneration of a tail. Students were investigating the role of gene abc in this process. They find that overexpressing abc in the head piece blocks tail regeneration. However, overexpressing constitutively active β-catenin along with abc in the severed head piece allows tail formation.

Which one of the following pathways correctly depicts the role of abc and β-catenin in planarian tail regeneration?

  1. qImage682dce1949547d925f93e8e4
  2. qImage682dce1a49547d925f93e8ed
  3. qImage682dce1a49547d925f93e8ee
  4. qImage682dce1b49547d925f93e8f3

Answer (Detailed Solution Below)

Option 1 : qImage682dce1949547d925f93e8e4

Developmental Biology Question 4 Detailed Solution

The correct answer is Option 1

Concept:

  • Planarians are flatworms known for their remarkable regenerative abilities. When they are cut transversely, they can regenerate both a head and a tail, depending on the signaling pathways activated in the respective body parts.
  • The Wnt signaling pathway is crucial for tail regeneration, and its activity is typically localized to the posterior region of the severed body segment.
  • β-catenin is a key component of the Wnt signaling pathway. Its activation promotes posterior identity, which is essential for tail regeneration.
  • β-catenin, which is a key effector in the Wnt signaling pathway, directly influences tail regeneration. When β-catenin is active, it can overcome the inhibition caused by abc, thus promoting tail regeneration.
  • Gene abc is hypothesized to play a role in modulating this process, and its overexpression impacts the regenerative outcome.

Explanation:

Role of abc in tail regeneration:

  • Overexpression of gene abc in the head piece blocks tail regeneration, suggesting that abc negatively interferes with the activity required for tail formation.
  • However, when constitutively active β-catenin is overexpressed along with abc in the severed head piece, tail formation is restored, indicating that β-catenin can override the inhibitory effect of abc.

Pathway depicted in Option 1:

  • Option 1 correctly shows that abc acts as an inhibitor in the tail regeneration process, but this inhibition can be counteracted by constitutive activation of β-catenin.
  • In this scenario, β-catenin re-establishes posterior identity and allows the regeneration of the tail despite the presence of abc overexpression.

Developmental Biology Question 5:

A tetraploid plant (4X = 60 chromosomes) reproduces by obligate apomixis. However, fertilization of the central cell is required for its proper endosperm development (pseudogamy). The male meiosis in this plant is normal, giving rise to reduced gametes. What will be the chromosome numbers in the embryo and endosperm of the apomictic seeds resulting from pseudogamy?

  1. Embryo = 30; endosperm = 90
  2. Embryo = 60; endosperm = 150
  3. Embryo = 60; endosperm = 90
  4. Embryo = 60; endosperm = 120

Answer (Detailed Solution Below)

Option 2 : Embryo = 60; endosperm = 150

Developmental Biology Question 5 Detailed Solution

The correct answer is Embryo = 60; Endosperm = 150

Concept:

  • A tetraploid plant has a chromosome number of 4X = 60, meaning its somatic cells contain 60 chromosomes.
  • In obligate apomixis, the embryo develops without fertilization from an unreduced egg cell (2n). This is a form of asexual reproduction, where the embryo is genetically identical to the parent plant.
  • In pseudogamy, fertilization of the central cell (which forms the endosperm) is required for proper endosperm development. The central cell is typically binucleate (2n + 2n), and fertilization by a reduced sperm cell (n) results in the triploid (3n) endosperm in most plants.

Explanation:

Chromosome number in the embryo:

  • As the embryo develops apomictically, it would retain the maternal chromosome number.
  • Since the plant is tetraploid with 4 sets of chromosomes (4X), the embryo will also have 4X chromosomes.
  • Therefore, in this case, the embryo will have 60 chromosomes.

Chromosome number in the endosperm:

  • The central cell in this tetraploid plant is binucleate (2n + 2n = 120 chromosomes). During pseudogamy, one reduced sperm cell (n = 30 chromosomes) fertilizes the central cell.
  • The resulting endosperm will have a chromosome number of 120 + 30 = 150 chromosomes.

Thus, the chromosome numbers in the embryo and endosperm of the apomictic seeds are 60 and 150, respectively.

Top Developmental Biology MCQ Objective Questions

Developmental Biology Question 6

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Which of the following is a part of apical meristem found in roots.

  1. Protoderm
  2. Axillary bud
  3. Differentiating vascular tissue
  4. Leaf primordium

Answer (Detailed Solution Below)

Option 1 : Protoderm

Developmental Biology Question 6 Detailed Solution

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The correct answer is Protoderm.

Key Points

  • Protoderm is the outermost primary meristem in plants.
  • In roots, it differentiates to form the epidermis.
  • Produces epidermal cells, including root hairs.
  • Root hairs play a crucial role in water and nutrient absorption.
  • Acts as a protective barrier.
  • Facilitates root-soil interactions.

Additional Information

  • Axillary buds, located at leaf-stem junctions, can grow into branches or flowers, influenced by hormonal signals and environmental factors. 
  • A leaf primordium is the initial embryonic tissue from which a leaf develops, found at the shoot apex or growing tip.
  • Vascular tissue in plants consists of xylem and phloem.
  • Xylem transports water and minerals from roots, providing structural support with tracheids, vessels, and fibers. 
  • Phloem transports sugars and nutrients throughout the plant.   
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Developmental Biology Question 7

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In Caenorhabditis elegans, blastomere identity occurs both through conditional and autonomous modes of cell specification. Which one of the following options is a correct statement in this regard?

  1. If the AB and P1 blastomeres are experimentally separated, the AB cell will generate all cells it would normally make.
  2. When AB divides to form daughter cells, ABp becomes different from ABa through its interaction with the P2 cell.
  3. The specification of AB cell is determined by the presence of cytoplasmic determinants.
  4. The P2 cell produces a morphogen for the determination of the ABp cell.

Answer (Detailed Solution Below)

Option 2 : When AB divides to form daughter cells, ABp becomes different from ABa through its interaction with the P2 cell.

Developmental Biology Question 7 Detailed Solution

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The correct answer is When AB divides to form daughter cells, ABp becomes different from ABa through its interaction with the P2 cell.

Concept: 

Autonomous Specification:

  • Autonomous specification refers to the inherent ability of a cell or group of cells to differentiate into specific cell types based on their intrinsic factors or developmental program.
  • Cells have the inherent potential to follow a predetermined developmental pathway and differentiate into specific cell types without relying heavily on external signals or interactions with neighboring cells.
  • Autonomous specification is often associated with the early stages of embryonic development, where cells possess predetermined information or cues that guide their differentiation.

  • One classic example of autonomous specification involves the early development of the nematode Caenorhabditis elegans.

Conditional Specification:

  • Conditional specification implies that the fate or differentiation of cells is influenced by external conditions, signals, or interactions with neighboring cells.
  • Cells may require specific signals, cues, or environmental factors to trigger their differentiation into particular cell types. In the absence of these external influences, the fate of the cells may be different.
  • Conditional specification is often observed in later stages of development, where cell fate decisions are influenced by the surrounding microenvironment or interactions with adjacent cells.

Explanation:

In Caenorhabditis elegans, the specification of blastomeres occurs through a combination of autonomous and conditional modes of cell fate determination:

  • ABp and ABa are the daughter cells formed when the AB cell divides. Initially, these cells are similar, but ABp becomes different from ABa due to its interaction with the neighboring P2 cell. This interaction is an example of conditional specification, where cell fate is influenced by external signals from neighboring cells.
  • Autonomous specification occurs in cells like the P1 blastomere, where cell fate is determined by internal cytoplasmic determinants.

Option 1: If the AB and P1 blastomeres are experimentally separated, AB will not generate all the cells it would normally make because some cell fates (like ABp) are determined conditionally through interaction with P2.
Option 3: The specification of the AB cell is not determined by the presence of cytoplasmic determinants. This applies more to P1 cells, which rely on autonomous specification.
Option 4: The P2 cell does not produce a general morphogen for the determination of ABp. Instead, it signals specifically to ABp via cell-cell interactions (such as the signaling molecule Notch/Delta).

MOM

Fig:Cell-cell signaling in the 4-cell embryo of C. elegans. The P2 cell produces two signals: (1) the juxtacrineprotein APX-1 (a Delta homologue), which is bound by GLP-1 (Notch) on the ABp cell, and (2) the paracrine protein MOM-2 (Wnt), which is bound by the MOM-5 (Frizzled) protein on the EMS cell. 

Conclusion:

Thus, Option 2 is the correct statement, as the ABp cell becomes different from ABa due to its interaction with the P2 cell, which is a form of conditional specification

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Developmental Biology Question 8

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In which of the following stages of Arabidopsis embryogenesis do the visible distinctions between the adaxial and abaxial tissues of the cotyledons become initially apparent?

  1. Globular stage
  2. Zygotic stage
  3. Torpedo stage
  4. Mature stage

Answer (Detailed Solution Below)

Option 3 : Torpedo stage

Developmental Biology Question 8 Detailed Solution

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The correct answer is Option 3 i.e. Torpedo stage.

Key Points

Arabidopsis Embryogenesis - 

  1.  The zygotic stage - haploid egg and sperm fuse to form a single-celled zygote, which is the initial stage of diploid life. Small apical and extended basal cells are produced during this stage of division.
  2. The globular stage embryo - An eight-cell (octant) globular embryo is produced by the apical cell following the first zygotic division, which occurs 30 hours after fertilization. Protoderm, which later develops into the epidermis, is created through cell division.
  3. The heart stage embryo - Two areas on either side of the eventual shoot apex undergo fast cell divisions to generate this stage. These two areas generate growths that subsequently give rise to the cotyledons, creating bilateral symmetry in the embryo.
  4. The torpedo stage embryo -  Caused by cell elongation along the embryonic axis and additional cotyledon development. The difference between the cotyledons' adaxial and abaxial tissue may be seen.
  5.  The maturation stage embryo - The embryo and seed lose water during the end of development and enter dormancy, becoming metabolically inactive. At advanced phases, the cell begins to collect storage chemicals. 

​F3 Vinanti Teaching 05.07.23 D8
Explanation:

Option 1 - INCORRECT

  • It involves the first division, which is the second stage of fertilization Hence no adaxial or abaxial axis is seen.

Option 2 - INCORRECT

  • It involves no division and is just the beginning of fertilization. Therefore, no axis is visible.

Option 3 - CORRECT

  • This stage involves rapid cell division at the embryo axis which leads to cell elongation such that the adaxial and abaxial axis are seen for the first time.

Option 4 - INCORRECT

  • This stage is the last stage of embryogenesis, which is the quiescent stage where the seeds enter dormancy.
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Developmental Biology Question 9

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Which one of the following statements about the cortical reaction in sea urchins is correct?

  1. The entry of Ca2+ ions into the egg initiates development.
  2. The exocytosed cortical granules during egg maturation contain the components of the zona pellucida.
  3. The depolarization of the plasma membrane after sperm entry helps to block polyspermy.
  4. The release of the cortical granules after sperm entry converts the vitelline membrane into the fertilization membrane which blocks polyspermy.

Answer (Detailed Solution Below)

Option 4 : The release of the cortical granules after sperm entry converts the vitelline membrane into the fertilization membrane which blocks polyspermy.

Developmental Biology Question 9 Detailed Solution

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The correct answer is The release of the cortical granules after sperm entry converts the vitelline membrane into the fertilization membrane which blocks polyspermy.

Explanation:

The cortical reaction is a crucial event in the process of fertilization, particularly in sea urchins, and it plays a key role in preventing polyspermy (the entry of more than one sperm into the egg).

  • After sperm entry, cortical granules located just beneath the plasma membrane of the egg are released (exocytosis) into the space between the plasma membrane and the vitelline membrane.
  • The contents of these cortical granules modify the vitelline membrane, converting it into the fertilization membrane, which serves as a physical barrier that prevents additional sperm from entering the egg, thus blocking polyspermy.

Other Options:

  • The entry of Ca²⁺ ions into the egg initiates development: While calcium is crucial for initiating the cortical reaction, development is not initiated solely by calcium entry.
  • The exocytosed cortical granules during egg maturation contain components of the zona pellucida: Sea urchins do not have a zona pellucida; this structure is present in mammals. The correct term here is vitelline membrane in sea urchins.
  • The depolarization of the plasma membrane after sperm entry helps to block polyspermy: This is related to the fast block to polyspermy, which occurs immediately after sperm entry, but it is not related to the cortical reaction (which is the slow block).

Thus, Option 4 correctly describes the role of the cortical reaction in preventing polyspermy by forming the fertilization membrane.

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Developmental Biology Question 10

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In animal cells, typically which organelle is only provided by the sperm to the oocyte following fertilization?

  1. Nucleolus
  2. Peroxisomes
  3. Mitochondria
  4. Centrioles

Answer (Detailed Solution Below)

Option 4 : Centrioles

Developmental Biology Question 10 Detailed Solution

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The correct answer is Centrioles.

Explanation:

During fertilization, the sperm contributes specific cellular components to the oocyte (egg), and the contribution of different organelles can vary:

  1. Nucleolus: The nucleolus is not specifically contributed by the sperm; it is a structure found in the nucleus of the oocyte.

  2. Peroxisomes: Peroxisomes are organelles involved in metabolic processes and are not uniquely provided by sperm during fertilization.

  3. Mitochondria: While sperm do contribute mitochondria, they are typically degraded after fertilization. In most animal species, the mitochondria in the zygote are predominantly derived from the oocyte, not the sperm.

  4. Centrioles: Centrioles are cylindrical structures involved in cell division. In many species, sperm contribute centrioles to the fertilized egg, which are important for organizing the mitotic spindle during the first cell division. The oocyte typically lacks centrioles, making the sperm's contribution crucial for proper cell division.

Summary: The centrioles provided by the sperm play an essential role in the early stages of development following fertilization, while other organelles are either derived from the oocyte or not specifically provided by the sperm. Thus, the correct answer is Centrioles.

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Developmental Biology Question 11

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What is the pattern of cleavage observed in mammals?

  1. Radial
  2. Spiral
  3. Rotational
  4. Bilateral

Answer (Detailed Solution Below)

Option 3 : Rotational

Developmental Biology Question 11 Detailed Solution

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The correct answer is Option 3 i.e.Rotational

Concept: 

  • Cleavage or cellulation is a series of mitotic cell divisions wherein the enormous volume of egg cytoplasm is divided into numerous smaller nucleated cells. 
  • The pattern of embryonic cleavage in a species is determined by two major factors:
    • The distribution and amount of the yolk in the cytoplasm.
    • Factors (mRNA, proteins) present in the cytoplasm of the egg cell. 
  • Types of cleavage - Holoblastic cleavage and meroblastic cleavage.

Holoblastic cleavage - 

  • In this type of cleavage, the yolk is present in a small amount and evenly distributed or the yolk is present in a moderate amount in a gradient.
  • In holoblastic cleavage, the first cleavage always occurs along the vegetal-animal axis of the egg, while the second cleavage is perpendicular to the first cleavage. 
  • From here the cleavage pattern varies in different species due to differences in the plane of the cleavage pattern. 
  • Types of holoblastic cleavage are as follows:
  1. Bilateral holoblastic cleavage- 
  • The first cleavage divides the zygote into left and right halves.
  • Cleavage planes of the following cleavages are centered on the axis and result in two halves that are the mirror image of one another.
  1. Radial holoblastic cleavage-
  • It is typically found in deuterostomes. 
  • The division planes are at 90-degree angles relative to one another.
  • The daughter cells (blastomeres) resulting from this division are aligned directly over or to the side of one another. 
  1. Rotational cleavage - 
  • It involves normal first division along the meridional axis, giving rise to two daughter cells. 
  • During the second cleavage division, one cell divides meridionally while the other divides equatorially.
  1. Spiral cleavage - 
  • It typically occurs in protostomes.
  • In this type of cleavage, the daughter cells (blastomeres) are not exactly aligned on top of one another, instead they are located at a slight angle. 
  • The first two cell divisions result in the four macromeres (A, B, C, D), each macromere representing one quadrant of the embryo. 

F2 Madhuri Teaching 23.08.2022 D2

Explanation: 

  • Cleavages in the mammalian egg are the slowest in the animal kingdom, about 12-24 hours apart. 
  • The first cleavage in mammals is along the meridional plane.
  • While in the second cleavage, one blastomere divides meridionally and another blastomere divides equatorially. 
  • This type of cleavage is rotational holoblastic cleavage. 

Hence the correct answer is option 3. 

  • ​
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Developmental Biology Question 12

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In a transplantation experiment, the area of presumptive ectoderm from an early frog gastrula was transplanted to a region of the newt gastrula destined to become parts of the mouth. The resulting salamander larvae had frog like mouth parts (frog tadpole suckers) instead of balancers as observed during development of wild type newt embryo. This is an example of

  1. Determination
  2. Genetic specificity of interaction
  3. Regional specificity of interaction
  4. Autonomous specification

Answer (Detailed Solution Below)

Option 2 : Genetic specificity of interaction

Developmental Biology Question 12 Detailed Solution

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The correct answer is Option 2 i.e. Genetic specificity of interaction.

Concept:

Determination:

  • This is a term in developmental biology that refers to the point in the developmental process at which a cell or group of cells becomes committed to a particular fate.
  • Once a cell's role is determined, the next steps are differentiation and morphogenesis which lead to the formation of a specific type of tissue or organ.
  • However, this determination is not always irreversible.

Genetic specificity of interaction:

  • This term refers to the concept that the fate of a cell or group of cells is determined by the specific genes they carry.
  • Genetic specificity implies that every cell or piece of tissue carries a specific set of genetic information that governs its development and dictates what form and function it will have, regardless of its environment.
  • When transplanted to a different location, these cells will still follow their inherent genetic program.

Regional specificity of interaction:

  • This concept suggests that a cell's or tissue's developmental behavior and fate might depend on its location within the embryo.
  • In other words, cells or tissues will interact with their immediate environment and adjust their developmental path based on these interactions.
  • Here, the environment and cell-to-cell interactions can influence the developmental outcome and modify a cell's fate from what was genetically programmed.

Autonomous specification:

  • This describes a mode of development in which the fate of a cell is established early on and is independent of interactions with neighboring cells.
  • Essentially, certain cells in the early embryo are programmed to follow a specific developmental path, regardless of their surroundings.
  • The genetic information in these cells directs them to form specific parts of the organism, even if they are isolated from the rest of the embryo or transplanted into a different region.
  • This is similar to the concept of genetic specificity but places more emphasis on the independence of the developmental path from neighboring cell influence.

Explanation

  • The transplanted frog tissue interacts with the newt embryo following the laws of its own species-specific developmental program.
  • Despite being placed into a different region and species, the transplanted tissue commits to developing into the structure it was originally destined to become, as per its inherent genetic program.
  • This shows that the developmental fate is attributed more to the genetic composition of the transplanted cells rather than the influence of their new location.
  • The interaction between the gene expression in the transplanted cells and the new host's cells results in the development of frog-like mouth parts in the newt larvae, illustrating the concept of genetic specificity of the interaction.
  • This is distinct from the concept of regional specificity of interaction which suggests that the fate of a cell or tissue is affected by its surrounding cells or tissues and will change its developmental path to match its new environment.
  • In this case, the cells contributed to the structure they were originally "programmed" to create via genetic specification, not the structure typical of the region to which they were transplanted.

Hence the correct answer is Option 2

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Developmental Biology Question 13

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During normal development of sea urchin, β‐catenin accumulates predominantly in the micromeres, which are fated to become endoderm and mesoderm. If GSK‐ 3 is blocked in the developing embryo:

  1. β‐catenin accumulation in the nuclei of large micromeres will be inhibited leading to formation of ectodermal ball.
  2. β‐catenin will accumulate in the nuclei of all blastula cells leading to an ectodermal ball.
  3. β‐catenin will accumulate in the nuclei of all blastula cells leading to animal cells getting specified as endoderm and mesoderm.
  4. β‐catenin which accumulate in the nuclei of large micromeres will be inhibited leading to animal cells getting specified as endoderm and mesoderm.

Answer (Detailed Solution Below)

Option 3 : β‐catenin will accumulate in the nuclei of all blastula cells leading to animal cells getting specified as endoderm and mesoderm.

Developmental Biology Question 13 Detailed Solution

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The correct answer is Option 3 i.e.β‐catenin will accumulate in the nuclei of all blastula cells leading to animal cells getting specified as endoderm and mesoderm.

Concept:-

  • Beta-catenin acts as a transcription factor in wnt signaling.
  • Beta-catenin is found throughout the embryo.
  • Beta-catenin is Active on the dorsal side.
  • GSK-3 inhibits Beta-catenin at the ventral side.
  •  During fertilization, Dsh and Wnt 11 protein from the vegetal pole translocated to the dorsal side of the egg.
  • Disheveled (Dsh) inhibits Gsk-3, thereby activating Beta-catenin.

F3 Vinanti Teaching 05.07.23 D9

Explanation:-

Option 1:- β‐catenin accumulation in the nuclei of large micromeres will be inhibited leading to formation of ectodermal ball.

  • GSK-3 inhibits beta-catenin. if GSK-3 is blocked, beta-catenin will be free, which will enter each nucleus of the vegetal pole and will form endoderm and mesoderm.
  • ​  Hence, this statement is incorrect.   

Option 2:-  β‐catenin will accumulate in the nuclei of all blastula cells leading to an ectodermal ball.

  • If beta-catenin will accumulate, it will form an endoderm and mesoderm, not the ectodermal ball.
  •  Hence, this option is incorrect.

Option 3:- β‐catenin will accumulate in the nuclei of all blastula cells leading to animal cells getting specified as endoderm and mesoderm.

  • Beta-catenin will get accumulated in the nuclei of all blastula cells which was earlier inhibited by GSK-3. Therefore, beta-catenin will form endoderm and mesoderm.
  • Hence, this option is correct.

Option 4:- β‐catenin which accumulates in the nuclei of large micromeres will be inhibited leading to animal cells getting specified as endoderm and mesoderm.

  • If GSK-3 is blocked, beta-catenin will enter each nucleus of all dorsal cells, it will not get inhibited.
  • Hence, this option is incorrect.
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Developmental Biology Question 14

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The following are sketches of wild-type and mutant (I - III) embryos of Drosophila melanogaster.

F1 Priya Teaching 21 10 2024 D2

Which one of the following options represents a correct match between the gene and its loss of function phenotype?

  1. dorsal : I
  2. torpedo : III
  3. gurken : II
  4. cactus : III

Answer (Detailed Solution Below)

Option 3 : gurken : II

Developmental Biology Question 14 Detailed Solution

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The correct answer is gurken : II

Concept:

  • Gurken (gene): This gene is essential for dorsal-ventral patterning in Drosophila. It encodes a protein involved in signaling from the oocyte to the surrounding follicle cells, influencing the patterning of the embryo. Loss of function of gurken leads to defective dorsal-ventral axis formation.
  • Dorsal (gene): Involved in specifying ventral structures. A loss of function leads to defects in ventral patterning, often resulting in an embryo that is fully dorsalized.
  • Torpedo (gene): This gene encodes a receptor that is part of the EGF signaling pathway, crucial for proper dorsal-ventral patterning. A loss of torpedo function also results in dorsal-ventral defects.
  • Cactus (gene): Acts as an inhibitor of Dorsal, regulating its nuclear localization. Loss of function in cactus leads to ventralization of the embryo.

Explanation:

  • Mutant I: This might show a phenotype corresponding to dorsalization, such as what is observed in dorsal mutants.
  • Mutant II: This indicates a dorsal-ventral patterning defect, characteristic of a gurken loss-of-function phenotype, where the embryo has lost proper dorsal-ventral polarity.
  • Mutant III: This might represent a cactus mutant, where the embryo becomes ventralized due to the uninhibited activity of the Dorsal protein.
  • Gurken loss-of-function: The embryo would lack the proper signaling for dorsal-ventral patterning, leading to a dorsalized phenotype, where the structures that would normally form along the dorsal side are missing. This is reflected in Mutant II, where the embryo lacks the proper dorsal-ventral axis.
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Developmental Biology Question 15

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Which one of the following statements regarding regeneration in Hydra is correct?

  1. It follows only stem cell-mediated regeneration.
  2. It follows only stem cell-mediated regeneration and morphallaxis.
  3. It follows stem cell-mediated regeneration, morphallaxis and epimorphosis.
  4. It follows only morphallaxis.

Answer (Detailed Solution Below)

Option 3 : It follows stem cell-mediated regeneration, morphallaxis and epimorphosis.

Developmental Biology Question 15 Detailed Solution

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The correct answer is It follows stem cell-mediated regeneration, morphallaxis and epimorphosis.

Concept:

Regeneration refers to the reactivation of the development in post-embryonic life so as to replace the missing tissues. Regeneration occurs in four major ways:

  1. Stem-cell mediated regeneration - In this type of regeneration, certain organs or tissues that are lost are regrow because of stem cells. For example, continuous replacement of blood cells from the bone marrow through hematopoietic stem cells.
  2. Epimorphosis - In this type of regeneration certain adult structure undergoes de-differentiation to from a relatively undifferentiated mass of cells that further undifferentiates to form a new structure. For example regeneration in flatworm and regeneration of amphibians limbs. 
  3. Morphallaxis - In this type of regeneration, certain existing tissues undergoes repatterning that results in new growth, even though only little new growth is seen. In this case, entire organism is regeneration from body pieces.
     For example, regeneration in hydra. 
  4. Compensatory regeneration - In this type of regeneration differentiated cells divide but they have maintain their differentiated function. In this case, new cells are produced but the does not comes from stem cells or from de-differentiated cells, rather each cells produces cells that is similar to itself. For example, mammalian liver shows compensatory regeneration. 

Explanation:

  • In hydra regeneration occurs through various mode of regeneration including stem cell-mediated regeneration, morphallaxis and epimorphosis.
  • In the case of hydra all cells of the body are replaced with new ones approximately every 20 days. This is possible due to present on stem cells population for all three cell-lineage (endodermal epithelial, ectodermal epithelial, and interstitial epithelial).
  • Hydra is know to developed missing body parts upon transverse or longitudinal amputation. Hence, hydra shows epimorphosis regeneration as well. 
  • Hydra shows morphallxis regeneration because pieces of body part can leads to generation of entire organism. When entire hydra is cut in several pieces then each piece will develop head at original apical end while it is develop foot at original basal end. 

Hence, the correct answer is Option 3. 

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