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Questions and Answers
In genomic imprinting, what is the role of the imprinting control region (ICR)?
In genomic imprinting, what is the role of the imprinting control region (ICR)?
- It activates transcription of the imprinted gene
- It is responsible for the removal of methylation in gamete forming cells
- It is only found in sperm cells
- It contains binding sites for transcription factors that regulate the imprinted gene (correct)
What happens to the pattern of methylation in gamete forming cells?
What happens to the pattern of methylation in gamete forming cells?
- Methylation is maintained
- Methylation is doubled
- Methylation is inherited from the previous generation
- Methylation is removed (correct)
What is the result of methylation on gene transcription?
What is the result of methylation on gene transcription?
- It activates gene transcription
- It inhibits gene transcription (correct)
- It has no effect on gene transcription
- It varies depending on the gene
What can be involved in genomic imprinting?
What can be involved in genomic imprinting?
In which species has genomic imprinting been observed?
In which species has genomic imprinting been observed?
What is the purpose of genomic imprinting in some species?
What is the purpose of genomic imprinting in some species?
What is epigenetic inheritance?
What is epigenetic inheritance?
What is the purpose of dosage compensation?
What is the purpose of dosage compensation?
Which of the following is a mechanism of dosage compensation in placental mammals?
Which of the following is a mechanism of dosage compensation in placental mammals?
What can cause epigenetic changes?
What can cause epigenetic changes?
What is the difference between epigenetic inheritance and genetic inheritance?
What is the difference between epigenetic inheritance and genetic inheritance?
In which species has dosage compensation been extensively studied?
In which species has dosage compensation been extensively studied?
What determines which X chromosome is inactivated in females?
What determines which X chromosome is inactivated in females?
What is the result of dosage compensation in females?
What is the result of dosage compensation in females?
What is the main function of Xic during X-chromosome inactivation?
What is the main function of Xic during X-chromosome inactivation?
What is the estimated percentage of X-linked genes in humans that may escape full inactivation?
What is the estimated percentage of X-linked genes in humans that may escape full inactivation?
What is the term for the phenomenon where a segment of DNA is marked and the effect is maintained throughout the life of the organism?
What is the term for the phenomenon where a segment of DNA is marked and the effect is maintained throughout the life of the organism?
Which allele of the Igf2 gene is transcribed into RNA?
Which allele of the Igf2 gene is transcribed into RNA?
What is the effect of inheriting an Igf2− allele from a male parent?
What is the effect of inheriting an Igf2− allele from a male parent?
What is the term for the phenomenon where only one allele of a gene is expressed, depending on its parental origin?
What is the term for the phenomenon where only one allele of a gene is expressed, depending on its parental origin?
What is the purpose of genomic imprinting?
What is the purpose of genomic imprinting?
What is the role of chromatin in genes that escape X-chromosome inactivation?
What is the role of chromatin in genes that escape X-chromosome inactivation?
Study Notes
Epigenetic Inheritance
- Epigenetic inheritance refers to a pattern in which a modification occurs to a nuclear gene or chromosome, altering gene expression, but the DNA sequence remains unchanged.
- Epigenetic changes are caused by DNA and chromosomal modifications that can occur during oogenesis, spermatogenesis, or early embryonic development.
Dosage Compensation
- Dosage compensation offsets differences in the number of active sex chromosomes.
- It has been studied in mammals, Drosophila, and Caenorhabditis elegans, with different mechanisms depending on the species.
- In placental mammals, one of the X chromosomes in somatic cells of females is inactivated, or the X chromosome from the male parent is inactivated, or either of the two X chromosomes is randomly inactivated.
Genomic Imprinting
- Genomic imprinting occurs in several species, including insects, mammals, and flowering plants, involving a single gene, part of a chromosome, an entire chromosome, or all chromosomes from one parent.
- It can be used for X inactivation in some species.
- Imprinting involves a marking process, with an imprinting control region (ICR) located near the imprinted gene, which is methylated either in the oocyte or sperm, but not both.
- For most genes, methylation causes inhibition of transcription.
Pattern of Methylation and X-Chromosome Inactivation
- Each parent inherits one methylated and one unmethylated gene, which is maintained in somatic cells, and methylation is removed in gamete-forming cells.
- The inactivated X chromosomes is maintained as such during subsequent cell divisions.
- Some genes on the inactivated X chromosome are expressed in somatic cells of adult female mammals, including pseudoautosomal genes, which do not require dosage compensation.
Genomic Imprinting and Gene Expression
- Genomic imprinting results in the expression of either the maternally-inherited or the paternally-inherited allele, but not both, a phenomenon known as monoallelic expression.
- The Igf2 gene in mice is an example of genomic imprinting, where the paternal allele is transcribed into RNA, but the maternal allele is not.
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Description
Test your understanding of epigenetic inheritance, including its definition, gene expression, and DNA modifications. Learn about the impact of epigenetic changes on gene regulation.
