Basic concepts of development MCQ Quiz in मल्याळम - Objective Question with Answer for Basic concepts of development - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

The correct answer is Option 2 i.e. A and B

Concept:

• In C. elegans, anchor cell formation is a crucial event during development. The anchor cell is a specialized cell that plays a key role in guiding the uterine and vulval cell fates.
• LIN-12 and LAG-2 are important proteins involved in this process.
• In the Z1 and Z2 cells, LIN-12 is a transmembrane receptor protein, and LAG-2 is its ligand.
• The anchor cell expresses LAG-2,which binds to LIN-12 receptor on the surface of neighboring Z1 and Z2 cells.
• This interaction triggers a cell signaling pathway that ultimately leads to the differentiation of the Z1 and Z2 cells into specific uterine and vulval precursor cells.
• Through this signaling, LIN-12 and LAG-2 regulate the fate decision.
• The cell which secretes the LAG-2  becomes the anchor cell and the cell which expresses the LIN-12 becomes the uterine precursor cell.

Explanation:

Statement A: CORRECT

• The cell which secretes LAG-2 becomes the anchor cell

Statement B: CORRECT

• The cell which express LIN-12 becomes the uterine precursor cell.

Statement C: INCORRECT

• The cells which secrete LIN-12 is becomes the uterine precursor cell not the anchor cell, while the cell which secretes LAG-2 becomes the anchor cell.

Statement D: INCORRECT

• There is no role of hippo kinase pathway in vulva formation in C. elegans.
• The hippo kinase pathway has a critical role in stem cell and tissue specific progenitor cell self-renewal and expansion.

Hence, the correct answer is Option 2.

Key Points

• The fate of a cell or a tissue refers to the specific type of cell or tissue it will differentiate into during development.
• The fate of a cell is determined by various factors, including intrinsic genetic programs and extrinsic signals from the surrounding environment.
• Different cells within an organism acquire distinct fates through a process known as cell fate specification.
• Cell fate specification involves a series of molecular events that drive cells to adopt specific identities and differentiate into particular cell types.
• These events are regulated by genetic and epigenetic factors that control gene expression and cellular responses to signals.
• During early development, cells often go through a process called lineage restriction, where they become progressively limited in their potential to differentiate into different cell types.
• This process is driven by the activation and repression of specific genes that guide cells along different developmental pathways.

Important Points
P. Equal to its normal fate in regulative development.

• This statement is incorrect.
• In regulative development, the fate of a cell or tissue is not predetermined but is influenced by its environment.
•  Cells in regulative development have the ability to change their fate and differentiate into different cell types based on the signals they receive from their surroundings.
• Therefore, the potency of a cell in regulative development is greater than its normal fate.

Q. Greater than its normal fate in regulative development.

• ​This statement is correct.
• As mentioned above, cells in regulative development have the potential to differentiate into different cell types depending on the signals they receive from the environment.
• Therefore, the potency of a cell in regulative development is greater than its normal fate.

R. Equal to its normal fate in mosaic development.

• ​This statement is correct.
• In mosaic development, the fate of a cell is predetermined and fixed.
• Each cell in a mosaic embryo is already determined to develop into a specific cell type, and this fate is not influenced by the surrounding environment.
• The potency of a cell in mosaic development is equal to its normal fate.

S. Greater than its normal fate in mosaic development.

• ​This statement is incorrect.
• In mosaic development, the fate of a cell is predetermined and fixed.
• Cells in a mosaic embryo do not have the ability to change their fate based on environmental signals.
• Therefore, the potency of a cell in mosaic development is not greater than its normal fate.​

​Hence the correct answer is option 1.

The correct answer is Option 2 i.e.B and C

Explanation-

• The C. elegans embryo uses both autonomous and conditional modes of specification.
• Conditional specification can be seen in the development of the endoderm cell lineage. At the 4-cell stage, the EMS cell requires a signal from its neighbor (and sister cell), the P2 blastomere.
• Usually, the EMS cell divides into an MS cell (which produces mesodermal muscles) and an E cell (which produces the intestinal endoderm).
• If the P2 cell is removed at the early 4-cell stage, the EMS cell will divide into two MS cells, and no endoderm will be produced.
• This instructive interaction with P2 is further confirmed by experiments that move P2 to the other side of the presumptive EMS blastomeres.
• This results in the two sides of EMS (E and MS) swapping fates. These results, taken together with others, show that it is this interaction with the P2 blastomere that specifies the differences between E and MS cell fates.
• The P2 cell produces the MOM-2 protein, a C. elegans Wnt protein.
• MOM-2 is received in the EMS cell by the MOM-5 protein, a C. elegans version of the Wnt receptor protein Frizzled.
• When the EMS cell divides, this signaling cascade is confined to the posterior daughter cell and downregulates the expression of the pop-1 gene. This induces the posterior daughter cell to become an E cell.
• The expression of the pop-1 gene in the anterior daughter cell results in it becoming an MS cell.
• In pop-1-deficient embryos, both EMS daughter cells become E cells 
   

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- Therefore, the correct statements are B and C

The correct answer is Option 2 i.e.The specification of dorso‐ventral axis in Drosophila.

Explanation-

• In Drosophila (fruit flies), the specification of the dorso-ventral axis is determined by maternal gene products present in the egg.
• These maternal gene products establish concentration gradients along the anterior-posterior and dorsal-ventral axes of the developing embryo.
• The fate of the maternal somatic cells is determined first, and this, in turn, influences the fate of the developing embryo.
• This process is a classic example of maternal effect genes or maternal effect determinants in embryonic development.
• Maternal effect genes such as bicoid and nanos play a key role in dorso-ventral axis specification.
• For example, bicoid mRNA is localized at the anterior end of the egg. After fertilization, the bicoid protein forms a concentration gradient along the anterior-posterior axis. High concentrations of bicoid specify anterior structures, while low concentrations specify posterior structures.

Concept:

• The C. elegans zygote exhibits rotational holoblastic cleavage.
• During early cleavage, each asymmetrical division produces one founder cell (denoted AB, MS, E, C, and D), which produces differentiated descendants, and one stem cell (the P1-P4 lineage).
• In the first cell division, the cleavage furrow is located asymmetrically along the anterior-posterior axis of the egg, closer to what will be the posterior pole. I
• t forms a founder cell (AB) and a stem cell (P1).
• During the second division, the anterior founder cell (AB) divides equatorially (longitudinally; 90° to the anterior-posterior axis), while the P1 cell divides meridionally (transversely) to produce another founder cell (EMS) and a posterior stem cell (P2).
• The stem cell lineage always undergoes meridional division to produce (1) an anterior founder cell and (2) a posterior cell that will continue the stem cell lineage.
• The descendants of each founder cell divide at specific times in ways that are nearly identical from individual to individual.
• In this way, the exactly 558 cells of the newly hatched larva are generated.
• The descendants of the founder cells can be observed through the transparent cuticle and are named according to their positions relative to their sister cells.

 Statement A:  P1 cell would develop autonomously while AB would show conditional development

• C. elegans demonstrates both the conditional and autonomous modes of cell specification.
• The P1 cell develops autonomously without the presence of AB.
• It makes all the cells that it would normally make, and the result is the posterior half of an embryo.
• However, the AB cell, in isolation, makes only a fraction of the cell types that it would normally make.
• For instance, the resulting ABa blastomere fails to make the anterior pharyngeal muscles that it would have made in an intact embryo.
• Therefore, the specification of the AB blastomere is conditional, and it needs the descendants of the P1 cell to interact with it.
•  thus this statement is true

 Statement B:  P1 cells would show conditional development while AB show autonomous development

• Consider the explanation above thus this statement is not true

 Statement C:  both would show autonomous specification and result in mosaic  development

• The determination of the P1 lineages also appears to be autonomous, with the cell fates determined by internal cytoplasmic factors rather than by interactions with neighboring cells.
• It is thought that protein factors might determine cell fate by entering the nuclei of the appropriate blastomeres and activating or repressing specific fate-determining genes.C. elegans embryo uses both autonomous and conditional modes of specification.
• Conditional specification can be seen in the development of the endoderm cell lineage.
•   thus this statement is not true

 Statement D:  both would show conditional specification and result in regulative development

•  Consider the explanation above thus this statement  is not true

 hence the correct answer is option 1

Concept:

• The inner cell mass (ICM) gives rise to the tissues of the embryo proper, while the outer cell mass forms the trophoblast, that later contributes to the placenta.
• Stem cells are defined as unspecialized cells which can differentiate into any cell type of an organism and also retain the capacity of self-renewal. Broadly, stem cells can be divided in five groups according to the degree of differentiation potential, i.e., (i) totipotent, (ii) pluripotent, (iii) multipotent, (iv) oligopotent and (v) unipotent stem cells.
•  Totipotent stem cells such as zygote and all cells in eight-cell stage morula possess the highest differentiation potential and capacity to form both embryo and extraembryonic structures including the placenta.
• Pluripotent stem cells retain the ability to differentiate into lineages of all three germ cell layers but cannot generate extraembryonic structures which include embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs).
•  ESCs are derived from the inner cell mass (ICM) of blastocysts of embryo whereas iPSCs are genetically reprogrammed and derived from the epiblast layer of implanted embryos.

​Explanation:

•  ESCs are derived from the inner cell mass (ICM),  provide their major contribution to embryogenesis through formation of germ layers as they have pluripotency potential and capacity for self-renewal.
• Retention of pluripotency of these stem cells depends on expression/level of transcription factors, i.e., SOX2, OCT4 and NANOG.
• During organogenesis, the altered expression of the molecules also influences these stem cells to lose their pluripotency and turn toward the lineage selection.
• As the differentiation progresses, the maintenance of the somatic cells including the oral squamous cells also depends on differential expression of the transcription factors to some extent.

​

  hence the correct answer is option 1

Concept:

• Wnt family members are best known for their roles in cell fate determination, differentiation, proliferation and apoptosis during embryonic development.
• Wnt signaling becomes effective during these cellular processes through the proper interaction between its ligands, receptors, effectors and inhibitors. 
• The relationship between Wnt signaling and implantation clearly reveals that, Wnt family members are critical for both early embryonic development and changing of the endometrium before implantation.
• Specific Wnt signaling pathway members are demonstrated to be critical for endometrial events such as decidualization and endometrial gland formation in addition to cyclic changes in the endometrium controlled by reproductive hormones.

• Consider the diagram above at resting stage i.e  (a): SFRP4 binds free WNT molecules in the extracellular space and DKK binds the LRP co-receptor.
• GSK3b phosphorylates CTNNB1 and causes ubiquitination and proteosomal degradation especially of β-catenin.
• In the nucleus transcription repressor Groucho protein family (TLE) suppresses members of the TCF/LEF transcription factor family and inhibits Wnt target gene transcription.
• However at Activated state i.e (b): A WNT ligand binds a FZD receptor/LRP co-receptor complex.
• As a result  β-catenin breaks from the APC/AXIN/GSK3b destruction complex in an unphosphorylated state.
• RSPO1 binds DKK to repress inhibition.
•  β-catenin translocates to the nucleus in an unphosphorylated form.
• It binds LEF/TCF transcription factor to regulate target gene expression.
• As wnt signaling is needed in embryonic development the expression of signaling cascade proteins increases and is thus relevant with graph of option 1 where GSK3b and β-catenin both increases.

​

hence the correct answer is option 1

Concept:

• Commitment is a cellular development process wherein cells are committed to specific cell fates and are capable to differentiates into particular types of cells. 
• The process of commitment is divided into two stages: 
  1. Specification - The fate of a particular cell or tissue is specified when it can differentiate autonomously when placed in a petri dish or test tube. This stage of commitment is still reversible.
  2. Determination - The fate of a particular cell or tissue is determined when it can differentiate autonomously when placed in another region of the embryo. This state of commitment is irreversible.

Following are the modes of cell type specification and their characteristics:

1. Autonomous specification - 
   • In this type of specification, the developing cells are able to differentiate into the same type of cells even without receiving external stimuli.
2. Conditional specification - 
   • In this type of specification, the fate of the cell is determined by its interaction with neighbouring cells.
3. Syncytial specification - 
   • In this type of specification, the interactions occur between parts of a single cell.
   • Syncytial means one cells have multiple nuclei, in this type of embryo karyokinesis is not followed by cytokinesis.

Important Points

Statement A: CORRECT

• Commitment is cell fate where the fate of the cells is already determined. 
• In the initial stage, committed cells may not appear any different than its neighbour.

Statement B: INCORRECT

• The first stage of commitment is called specification. 
• At this stage, the commitment is still liable.
• The cells are able to differentiate autonomously and their fate is still reversible.

Statement C: CORRECT

• The second stage of commitment is determination. 
• At this stage, the fate of cells is irreversible.
• Cells are said to be determined if they are capable of differentiating even if they are placed in different parts of the embryo.

Statement D: CORRECT

• Cytoskeletal helps to maintain the positioning of nuclei in the syncytium egg of drosophila.
• It helps to establish a gradient of morphogens. 
• The concentration of bicoid is high in the anterior region and its gradient decreases from anterior to posterior. 
• While the concentration of caudal is high at the posterior region and its gradient decreases from posterior to anterior.

Statement E: INCORRECT

• In mosaic development, the fate of a cell is dependent on its lineage, and the position of these cells in the embryo is irrelevant to its fate. 
• If any blastomere is missing then the embryo will lack those parts or tissues that normally would have been produced by these missing blastomere.

Hence, the correct answer is option 4. 

Concept: 

• Cleavage refers to a series of mitotic divisions of the zygote that immediately follow after fertilization, here enormous volume of egg cytoplasm is divided into numerous smaller, nucleated cells.
• In mammals, cleavage is called rotational cleavage. 
• The first cleavage is meridional and results in two daughters. 
• In the second cleavage, one blastomere divides meridionally while the second blastomere divides equatorially. 
• In the third cleavage, the embryo reaches the 8-celled stage and after the fourth cleavage, the embryo reaches the 16-celled stage called morula.
• Morula consists of a larger group of external cells surrounder the inner and a smaller group of internal cells.
• The descendant of the external cells gives rise to trophoblast cells, these cells develop into chorions that form the placenta. Also, these cells do not form any embryonic structures.
• The descendant of the internal cells gives rise to inner mass cells (IMC) that form the embryo proper, yolk sac, allantois, and amnion. 
• At 64-celled stages, trophoblast and inner mass cells (IMC) can be seen in separate layers.
• Initially, the morula does not have any cavity, but later during a process of cavitation, trophoblast cells secrete fluid that will form blastocoel. 
• This blastocyst is the hallmark of embryonic cleavage.

Important Points

Option 1: INCORRECT

• Totipotent cells are those types of cells that can form all different cell types in a body, including the extraembryonic, or placental, cells.
• After fertilisation, the first couple of cell divisions will result in the formation of cells that are totipotent. 

Option 2: CORRECT

• Pluripotent cells are those types of cells that can form all of the cell types that make up the body
  Inner mass cell (IMC) are considered pluripotent as they give rise to embryo proper from which all types of cells are derived.  

Option 3: INCORRECT

• Multipotent cells are those that can develop into more than one cell type although they are more limited than pluripotent cells. 
• So, this type of cell do not form all the types of cell of the embryo while ICM can form all types of cells. 

Option 4: INCORRECT

• Unipotent cells are those that can form only one type of cell. 
• For example, epidermal stem cells can form only cells of the skin. 

Hence, the correct answer is option 2. 

Concept:

• Cleavage is a series of mitotic cell divisions that immediately follows fertilization, which divided a zygote into numerous smaller, nucleated cells. 
• Cleavage sets the groundwork for the next stage of embryo development, i.e., gastrulation. 
• The following are different planes of cleavage:

1. Meridional plane of cleavage: In this case, the furrow passes through the median axis or centre of the egg and bisects both poles of the egg. 
2. Vertical plane of cleavage: In this case, the furrows pass in any direction except the median axis, from the animal to the opposite pole. 
3. Equatorial plane of cleavage: In this case, the cleavage plane divides the egg only halfway between the animal and vegetal poles. The plane of division is the right angle to the median axis.
4. Latitudinal plane of cleavage: It is similar to that of the equatorial plane of division and furrows run through the cytoplasm on either side of the equatorial plane.

Important Points

​Option 1: CORRECT

• In the case of superficial cleavage, nucleus division takes place but cytokinesis does not occur, where the yolk is positioned to the centre of the cell and nuclei migrate to the periphery of the egg. 
• Centrolecithal eggs have yolk at the centre of the egg.
• Hence, this is the correct answer.

Option 2: INCORRECT

• In radial cleavage, daughter cells are arranged exactly on top of one another. 
• The cell division is complete, where karyokinesis is followed by cytokinesis. 

Option 3: INCORRECT

• In this case, the plane of the first cleavage furrow determines the plane of bilateral symmetry. The first cleavage bisects the embryo into right and left halves.

Option 4: INCORRECT

• In discoidal cleavage, the cell division is only restricted to the small disc of cytoplasm at the animal pole, as cleavage furrows cannot penetrate the yolk.

Hence, the correct answer is option 1.