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Questions and Answers
In genomic imprinting, which of the following can be imprinted?
In genomic imprinting, which of the following can be imprinted?
What is the molecular mechanism involved in genomic imprinting?
What is the molecular mechanism involved in genomic imprinting?
What happens to the methylation pattern in gamete-forming cells?
What happens to the methylation pattern in gamete-forming cells?
What is the function of the imprinting control region (ICR)?
What is the function of the imprinting control region (ICR)?
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What is the effect of methylation on gene expression?
What is the effect of methylation on gene expression?
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In which species has genomic imprinting been observed?
In which species has genomic imprinting been observed?
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What is the main function of the Xic during X-chromosome inactivation?
What is the main function of the Xic during X-chromosome inactivation?
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What is the process by which the imprint is established during gametogenesis?
What is the process by which the imprint is established during gametogenesis?
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Which type of genes are expressed in the somatic cells of adult female mammals despite being on the inactivated X chromosome?
Which type of genes are expressed in the somatic cells of adult female mammals despite being on the inactivated X chromosome?
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What is the main characteristic of genomic imprinting?
What is the main characteristic of genomic imprinting?
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Which of the following is NOT a stage of genomic imprinting?
Which of the following is NOT a stage of genomic imprinting?
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What is the result of genomic imprinting on the Igf2 gene?
What is the result of genomic imprinting on the Igf2 gene?
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What is the effect of an Igf2 gene mutation on the size of a mouse?
What is the effect of an Igf2 gene mutation on the size of a mouse?
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During which stage of development is the imprint pattern maintained?
During which stage of development is the imprint pattern maintained?
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Which allele is transcribed into RNA in the Igf2 gene?
Which allele is transcribed into RNA in the Igf2 gene?
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What is the result of genomic imprinting in the Igf2 gene?
What is the result of genomic imprinting in the Igf2 gene?
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What happens to the maternal Igf2- allele after fertilization?
What happens to the maternal Igf2- allele after fertilization?
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In which cells is the imprint erased?
In which cells is the imprint erased?
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What is the term used to describe the expression of either the maternal or paternal allele, but not both?
What is the term used to describe the expression of either the maternal or paternal allele, but not both?
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What is the term used to describe the phenomenon of a segment of DNA being marked and the effect being maintained throughout the life of the organism inheriting the marked DNA?
What is the term used to describe the phenomenon of a segment of DNA being marked and the effect being maintained throughout the life of the organism inheriting the marked DNA?
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What is the result of genomic imprinting in the female mouse?
What is the result of genomic imprinting in the female mouse?
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What is genomic imprinting an example of?
What is genomic imprinting an example of?
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Study Notes
Genomic Imprinting
- Genomic imprinting occurs in several species, including insects, mammals, and flowering plants.
- It can involve a single gene, a part of a chromosome, an entire chromosome, or even all the chromosomes from one parent.
- Genomic imprinting can be used for X inactivation in some species.
Imprinting and DNA Methylation
- Genomic imprinting involves a marking process at the molecular level.
- The imprinting of several genes involves an imprinting control region (ICR) located near the imprinted gene.
- The ICR is methylated either in the oocyte or sperm, but not both.
- The ICR contains binding sites for one or more transcription factors that regulate the imprinted gene.
- For most genes, methylation causes inhibition of transcription.
Pattern of Methylation
- Each parent inherits one methylated and one unmethylated gene, which is maintained in somatic cells.
- Methylation is removed in gamete-forming cells.
X-Chromosome Inactivation
- The inactivated X chromosome is maintained as such during subsequent cell divisions.
- Some genes on the inactivated X chromosome are expressed in the somatic cells of adult female mammals.
- Dosage compensation is unnecessary for these genes because they are located on both the X and Y chromosomes.
- Up to a quarter of X-linked genes in humans may escape full inactivation.
Genomic Imprinting
- Genomic imprinting is a phenomenon in which a segment of DNA is marked, and the effect is maintained throughout the life of the organism.
- The offspring expresses either the maternally-inherited or the paternally-inherited allele, but not both (monoallelic expression).
Mouse Igf2 Gene as an Example of Genomic Imprinting
- The Igf2 gene codes for a growth hormone called insulin-like growth factor 2.
- A functional Igf2 gene is necessary for normal size.
- Imprinting results in the expression of the paternal but not the maternal allele.
- The paternal allele is transcribed into RNA, while the maternal allele is not transcribed.
Stages of Imprinting
- Imprinting can be divided into three stages:
- Establishment of the imprint during gametogenesis
- Maintenance of the imprint during embryogenesis and in adult somatic cells
- Erasure and reestablishment of the imprint in the germ cells
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Description
This quiz covers the concept of genomic imprinting in various species, including its involvement in DNA methylation and X inactivation. Learn about the different levels of genomic imprinting, from single genes to entire chromosomes.
