Embryology

1. Which of the following best describes bivalency in embryonic stem cells?

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שאלה #182847

		The presence of two copies of each chromosome
		A chromatin state marked by both activating and repressive histone modifications
		The pairing of maternal and paternal alleles
		The process of silencing both X chromosomes in female embryos
		The duplication of gene regulatory sequences

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2. Genomic imprinting is an epigenetic process that results in:

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שאלה #182850

		Equal expression of both maternal and paternal alleles
		Silencing of one X chromosome in males
		Expression of a gene from only one parent, depending on its origin
		Increased mutation rates during early development
		Bivalent chromatin modifications at all promoter regions

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4. Which epigenetic modification is most directly associated with maintaining genomic imprinting?

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שאלה #182852

		Histone acetylation
		Histone methylation
		DNA methylation
		Alternative splicing
		Xist RNA expression

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5. During early embryonic development, bivalent chromatin marks are important because they:

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שאלה #182854

		Prevent X-inactivation from occurring too early
		Directly promote genomic imprinting of autosomal genes
		Keep developmental genes poised for activation or repression
		Mark inactive alleles for permanent silencing
		Reflect errors in chromatin remodeling

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6. Which of the following best explains how imprinting influences gene expression and maintains appropriate dosage?

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שאלה #182856

		Imprinted genes are randomly silenced on either the maternal or paternal allele in each cell, leading to monoallelic expression and reduced dosage variability.
		Imprinting involves DNA methylation marks established during gametogenesis that selectively silence one parental allele, ensuring parent- of-origin-specific monoallelic expression.
		Imprinted genes are silenced only if inherited from the mother, preventing maternal overexpression and maintaining balance with paternal alleles.
		Imprinting activates both alleles of growth-promoting genes, ensuring that embryonic tissues have sufficient gene product for rapid growth.

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8. You isolate DNA and mRNA from an entire embryo and analyze the sequence of a specific gene. You find two different versions of DNA sequence of that gene but only one version of mRNA. What could explain this?

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שאלה #182857

		Histone methylation
		X-inactivation
		Imprinting
		Bivalent chromatin
		Histone acetylation

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9. When a horse and donkey hybridize, the phenotype of the offspring (mule or hinny) depends on which species is the mother and which is the father. How is this phenomenon associated with genomic imprinting?

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שאלה #182859

		Imprinting involves the random silencing of one allele, so hybrid offspring may fail to express key genes if both alleles are randomly silenced.
		Hybrid offspring show different phenotypes depending on which species contributes which set of imprinted genes
		Only maternal imprints are functional in early development, so hybrid viability depends solely on the mother's species.
		Imprinting leads to X-chromosome inactivation in males, which differs between species and causes developmental failure in male hybrids.

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11. Which of the following concepts are represented by the modern version of the Waddington epigenetic landscape (i.e., the analogy of cells as marbles rolling down branching valleys during development)?

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שאלה #182861

		A. Cell differentiation is always irreversible
		B. Cells transition through flexible intermediate states before committing to specific lineages
		C. Cellular plasticity allows for trans-differentiation or reprogramming under certain conditions.
		D. Distinguishing between juxtacrine and paracrine signaling.
		E. A+B
		F. B+C

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12. Which answer represents best our modern view on the recapitulation theory?

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שאלה #182862

		The theory is completely wrong
		The theory correctly predicted that embryos develop by pre-formation rather than epigenesis
		Evolution is NOT recapitulated in development, but certain aspects— such as genetic programs—can be
		The theory is completely wrong

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13. When choosing model organisms to study embryonic development, which considerations are important?

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שאלה #182864

		A. Embryo transparency
		B. Development in egg or uterus
		C. Sequenced genome
		D. Availability of genetic strains
		E. All of the above
		F. A+C+D

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Discuss, Learn and be Happy דיון בשאלות

1. Which of the following best describes bivalency in embryonic stem cells?

2. Genomic imprinting is an epigenetic process that results in:

4. Which epigenetic modification is most directly associated with maintaining genomic imprinting?

5. During early embryonic development, bivalent chromatin marks are important because they:

6. Which of the following best explains how imprinting influences gene expression and maintains appropriate dosage?

8. You isolate DNA and mRNA from an entire embryo and analyze the sequence of a specific gene. You find two different versions of DNA sequence of that gene but only one version of mRNA. What could explain this?

9. When a horse and donkey hybridize, the phenotype of the offspring (mule or hinny) depends on which species is the mother and which is the father. How is this phenomenon associated with genomic imprinting?

11. Which of the following concepts are represented by the modern version of the Waddington epigenetic landscape (i.e., the analogy of cells as marbles rolling down branching valleys during development)?

12. Which answer represents best our modern view on the recapitulation theory?

13. When choosing model organisms to study embryonic development, which considerations are important?

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