Embryonic Development and Cancer
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Which of the following best describes the relationship between cell division, cell differentiation, and morphogenesis in embryonic development?

  • Cell division generates the necessary cells, cell differentiation specializes them, and morphogenesis organizes them into the organism's form. (correct)
  • These three processes occur independently and do not influence each other during embryonic development.
  • Cell differentiation drives cell division, which in turn directs morphogenesis.
  • Morphogenesis initiates cell division, which subsequently leads to cell differentiation.

Cytoplasmic determinants and cell-cell signaling (induction) both play a role in cell differentiation. How do they differ in their mechanism of action?

  • Cytoplasmic determinants involve direct physical contact between cells, while induction relies on secreted molecules.
  • Cytoplasmic determinants are inherited from the mother and affect early cell fates, while induction involves signals between cells that influence later development. (correct)
  • Cytoplasmic determinants affect only the cells that originally contain them, while induction affects all cells in the developing embryo equally.
  • Cytoplasmic determinants are evenly distributed throughout the zygote, while induction is localized to specific regions.

A researcher is studying a mutation that disrupts the normal development of a frog embryo. They observe that certain cells fail to differentiate into their expected cell types. Which of the following is LEAST likely to be the cause of this?

  • Increased histone acetylation near genes required for cell differentiation. (correct)
  • A defect in the distribution of cytoplasmic determinants in the egg.
  • A failure of cells to undergo mitosis and proper cell division.
  • A disruption in the cell signaling pathways required for induction.

Proto-oncogenes can be converted to oncogenes by certain genetic mutations. Which of the following mutations would be LEAST likely to result in an oncogene?

<p>A mutation that introduces a premature stop codon, resulting in a truncated, non-functional protein. (D)</p> Signup and view all the answers

The ras gene and the p53 gene are both frequently mutated in cancer cells. What is the key functional difference between these two genes in preventing cancer?

<p>The <em>ras</em> gene is a proto-oncogene involved in cell signaling pathways that promote cell division, while the <em>p53</em> gene is a tumor suppressor gene that can halt cell cycle progression or trigger apoptosis in response to DNA damage. (D)</p> Signup and view all the answers

Which of the following best explains why cloned embryos often exhibit developmental defects?

<p>Fully differentiated cells have accumulated epigenetic changes in their DNA. (D)</p> Signup and view all the answers

How do induced pluripotent stem cells (iPS) differ from adult stem cells?

<p>iPS cells are created by 'reprogramming' differentiated cells to become pluripotent, while adult stem cells are naturally multipotent. (B)</p> Signup and view all the answers

A researcher is studying a gene that, when mutated, leads to excessive cell division. This gene is most likely a(n):

<p>Proto-oncogene. (D)</p> Signup and view all the answers

In the context of the stickleback fish, what is the role of the Pitx1 gene?

<p>Influencing the development of the pelvic bone. (B)</p> Signup and view all the answers

Which of the following is the correct order of steps in using stem cells for disease treatment, starting from a patient's skin cells?

<p>Remove skin cells -&gt; Reprogram skin cells -&gt; Differentiate into specific cell type -&gt; Return cells to patient (B)</p> Signup and view all the answers

If a mutation causes a protein, normally responsible for inhibiting cell division, to be absent, what is the most likely consequence?

<p>The cell cycle will not be inhibited. (A)</p> Signup and view all the answers

Why is the zygote considered totipotent?

<p>It can give rise to all the different cell types in an organism (B)</p> Signup and view all the answers

Which of the following best describes the role of regulatory genes and transcription factors in cell differentiation?

<p>They direct the irreversible series of events leading to cell differentiation. (B)</p> Signup and view all the answers

During embryonic development, excess cells are produced, and some undergo programmed cell death. Which of the following proteins is most directly involved in executing this process?

<p>Caspases (C)</p> Signup and view all the answers

How might mutations in the human Pitx1 gene manifest?

<p>Defects in upper limbs or feet. (B)</p> Signup and view all the answers

Which of the following is the LEAST accurate description of 'determination' in the context of cell differentiation?

<p>A stage where cells can still differentiate into any cell type. (C)</p> Signup and view all the answers

A mutation in a homeotic gene leads to the development of legs in place of antennae in an insect. What does this demonstrate about the function of homeotic genes?

<p>They act as master control genes that direct pattern formation. (A)</p> Signup and view all the answers

What would be the likeliest outcome of a mutation that disrupts the normal distribution of morphogens in an early embryo?

<p>Disruptions in the establishment of body axes. (A)</p> Signup and view all the answers

If a researcher introduces a MyoD protein into a fibroblast cell (a cell that does not normally differentiate into muscle), what is the most likely outcome?

<p>The fibroblast may begin to express muscle-specific genes. (B)</p> Signup and view all the answers

During limb development, apoptosis sculpts the digits (fingers and toes) by removing the interdigital tissue. If apoptosis is inhibited during limb development, what is the likely result?

<p>The digits will remain webbed. (A)</p> Signup and view all the answers

Which of the following accurately orders the stages of development, from least to most differentiated?

<p>Totipotent → Pluripotent → Unipotent (A)</p> Signup and view all the answers

A mutation in a proto-oncogene can lead to cancer by which of the following mechanisms?

<p>Creating a hyperactive or degradation-resistant protein. (A)</p> Signup and view all the answers

Which of the following genetic changes could result in a proto-oncogene becoming an oncogene?

<p>A point mutation within a control element, leading to excessive production of a normal growth-stimulating protein. (A)</p> Signup and view all the answers

The Ras gene stimulates the cell cycle and is a proto-oncogene. In approximately what percentage of cancers do mutations of the Ras gene occur?

<p>30% (A)</p> Signup and view all the answers

What is the primary function of the p53 gene in preventing cancer?

<p>Halting the cell cycle for DNA repair and activating apoptosis if necessary. (D)</p> Signup and view all the answers

Loss of function of the p53 gene is implicated in approximately what percentage of cancers?

<p>Over 50% (C)</p> Signup and view all the answers

During colon cancer progression, which of the following represents a typical sequence of events?

<p>Activation of oncogene → loss of SMAD4 → loss of p53. (A)</p> Signup and view all the answers

Why does the likelihood of developing cancer increase with age?

<p>The chance of accumulating multiple mutations in DNA increases over time. (D)</p> Signup and view all the answers

How does chemotherapy work to stop cancer cells from growing?

<p>By preventing hormones from binding to their receptors on cancer cells, signaling them to stop growing. (C)</p> Signup and view all the answers

Flashcards

DNA Methylation

Adding methyl groups to DNA, affecting gene expression.

Histone Acetylation

Addition of acetyl groups to histone proteins, loosening DNA and increasing transcription.

Activators & Repressors

Proteins that promote or inhibit gene transcription by binding to DNA sequences.

Embryonic Development

The transformation from a zygote into a multicellular organism.

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Cytoplasmic Determinants

Maternal substances in the egg distributed unevenly, influencing early cell development.

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Induction

Signaling molecules from nearby cells induce changes in a target cell.

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Determination

An irreversible process where a cell becomes committed to a specific fate.

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Regulatory Genes

Genes coding for proteins that regulate the expression of other genes, directing cell differentiation.

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Apoptosis

Programmed cell death, essential for sculpting tissues and organs during development.

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Pattern Formation

Setting up the body plan with axes (dorsal-ventral, anterior-posterior, left-right) in an embryo.

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Morphogens

Unevenly distributed substances that establish an embryo’s axes.

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Homeotic Genes

Master control genes that regulate pattern formation during development.

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MyoD Protein

Transcription factors that bind to DNA and stimulate the transcription of specific genes; involved in muscle cell differentiation.

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Pitx1 Gene

Homeotic (Hox) genes that control the development of body structures along the body axis.

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Nuclear Transplantation

Replacing a nucleus from an egg cell with a nucleus from a differentiated cell to create a cloned organism.

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Stem Cells

Cells capable of self-renewal and differentiation into specialized cells.

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Totipotent

Can differentiate into ANY cell type in the body.

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Pluripotent

Can differentiate into MANY cell types, but not all (e.g., embryonic stem cells).

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Multipotent

Can differentiate into a FEW cell types (e.g., adult stem cells).

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Proto-oncogenes

Normal genes that promote cell growth and division.

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Tumor-suppressor genes

Genes that inhibit cell division and prevent uncontrolled growth.

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Oncogene

A mutated proto-oncogene that causes excessive cell growth and division, leading to cancer.

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Ras gene

A proto-oncogene that stimulates the cell cycle. Mutations occur in ~30% of cancers.

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p53 gene

A tumor-suppressor gene that halts the cell cycle for DNA repair or activates apoptosis. Mutations occur in 50% of cancers

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Translocation/Transposition

When chromosomes switch places, or genes move locations causing cancer

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Gene amplification

Producing many copies of a gene, leading to an excess of the protein it encodes. Can lead to cancer

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Chemotherapy

Drugs that block hormone-receptor binding to stop cell growth. Used in cancer treatment.

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Study Notes

  • Differential gene expression programs the different cell types in a multicellular organism.
  • Timing and coordination of specific events are regulated in normal development.
  • Pattern formation and induction are key components of normal development.
  • Gene regulation plays a significant role in embryonic development and cancer.

Embryonic Development

  • Features three key processes from zygote to organism.
  • Cell division increases the number of identical cells through mitosis.
  • Cell differentiation specializes cells in structure and function.
  • Morphogenesis is the "creation of form," shaping the organism.

Cytoplasmic Determinants

  • Maternal substances are unevenly distributed in the egg and early embryo.
  • Molecules of different cytoplasmic determinants are localized within the egg.

Cell-Cell Signals

  • Induction triggers cells to differentiate via signals from neighboring cells.
  • Cell-cell signals involve molecules produced by one cell influencing adjacent cells, with growth factors as an example.

Determination and Cell Differentiation

  • Determination is an irreversible process that leads to cell differentiation.
  • Cells progress from totipotent to pluripotent to unipotent states, restricting their developmental potential.

Regulatory Genes and Transcription Factors

  • Regulatory genes and transcription factors directly orchestrate cell differentiation.
  • The master regulatory gene myoD is used as an example.

Apoptosis

  • Apoptosis, or programmed cell death, sculpts organs and tissues.
  • The process is carried out by caspase proteins.

Pattern Formation

  • Pattern formation establishes the body plan (head, tail, left/right, back/front) through cytoplasmic determinants and inductive signals.

Morphogens

  • Morphogens are substances unevenly distributed to establish the embryo's axes.
  • Bicoid mRNA and protein in Drosophila development for anterior-posterior axis determination, are key examples.

Homeotic Genes

  • Homeotic genes are master control genes that govern pattern formation, and Hox genes are an example.
  • Mutations in these genes can cause misplacement of structures.

Pitx1 Gene

  • The Pitx1 gene acts can be both homeotic and Hox gene.
  • Development of pelvic bone in stickleback fish is governed by this gene
  • Development of the anterior structures, brain and hindlimbs are governed by the same gene in humans
  • Mutation in the human variant may cause clubfoot, polydactyly and defects in upper limbs.

Cloning

  • Cloning shows differentiated cells can be "reprogrammed" to produce stem cells.

Nuclear Transplantation

  • It involves removing the nucleus of an egg cell and replacing it with a nucleus from a differentiated cell.

Reproductive Cloning Problems

  • Reproductive cloning can result in various defects in cloned embryos.
  • DNA from fully differentiated cells often have epigenetic changes that interfere with proper development.

Stem Cells

  • Stem cells can reproduce indefinitely and produce other specialized cells.
  • Stem cells can be totipotent (zygote), pluripotent (embryonic stem cells), or multipotent (adult stem cells/induced pluripotent stem cells).

Stem Cell Types

  • Embryonic stem cells can generate all embryonic cell types
  • Adult stem cells can generate a limited number of cell types.

Disease Treatment

  • Stem cells can be used to treat a variety of diseases
  • Skin cells from a patient can be reprogrammed to become induced pluripotent stem (iPS) cells, and then treated so they will diffentiate into a specific cell type.
  • These new versions of specific cells can then be returned to the patient with impaired tissue and can then repair it.

Cancer Risks

  • Abnormal regulation of genes affecting the cell cycle can lead to cancer.
  • Proto-oncogenes promote cell growth, whereas tumor-suppressor genes inhibit cell division
  • Active oncogenes and loss of tumor-suppressor genes can drive cancer development.
  • The risk of cancer increases with age and the accumulation of mutations.

Proto-oncogenes Mutation

  • Proto-oncogenes stimulate normal cell growth and division.
  • A proto-oncogene will have a mutation and become an Oncogene.
  • The products of photo-oncogenes are more present then normal.

Cancer Genes

  • The ras gene is a proto-oncogene that stimulates the cell cycle.
  • Mutations in ras are found in 30% of cancers.
  • The p53 gene is a tumor-suppressor gene that functions to stop the cell cycle for DNA repair.
  • Mutations in p53 are implicated in over 50% of cancers.

Cancer Development

  • Cancer development involves accumulation of mutations which results in active oncogenes, and tumor- suppressing genes loss

Chemotherapy

  • Chemotherapy blocks hormones from binding to their receptors and blocks the cell cycle.
  • Receptor-positive cells respond better than cells without receptors.

Triple Negative Breast Cancer

  • Many breast cancer cells have either 1, 2 or 3 of these receptors on their surface.
  • Chemotherapy will attach to these receptors and block the cell cycle.
  • TNBC Cancer is the lack of 3 receptors on the cell surface.

Cancer and Embryonic Development

  • Embryonic development proceeds correctly with proper gene regulation.
  • Cancer development is caused by when gene regulation goes awry.

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Development, Stem Cells & Cancer PDF

Description

Explore key concepts in embryonic development, including cell division, differentiation, and morphogenesis. Differentiate between cytoplasmic determinants and cell-cell signaling. Also, investigate the roles of proto-oncogenes, tumor suppressor genes (like p53), and stem cells in development and cancer.

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