Non-Mendelian Inheritance (Medium)

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Questions and Answers

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?

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?

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?

Any of the above Signup and view all the answers

In which species has genomic imprinting been observed?

In several species, including insects, mammals, and flowering plants Signup and view all the answers

What is the purpose of genomic imprinting in some species?

To activate X inactivation Signup and view all the answers

What is epigenetic inheritance?

A modification that alters gene expression, but does not change the DNA sequence Signup and view all the answers

What is the purpose of dosage compensation?

To compensate for differences in the number of active sex chromosomes Signup and view all the answers

Which of the following is a mechanism of dosage compensation in placental mammals?

Inactivating one of the X chromosomes in somatic cells of females Signup and view all the answers

What can cause epigenetic changes?

DNA and chromosomal modifications Signup and view all the answers

What is the difference between epigenetic inheritance and genetic inheritance?

Epigenetic inheritance does not change the DNA sequence, while genetic inheritance does Signup and view all the answers

In which species has dosage compensation been extensively studied?

Placental mammals, Drosophila, and Caenorhabditis elegans Signup and view all the answers

What determines which X chromosome is inactivated in females?

Random inactivation Signup and view all the answers

What is the result of dosage compensation in females?

One X chromosome is inactivated, resulting in equal gene expression with males Signup and view all the answers

What is the main function of Xic during X-chromosome inactivation?

To maintain the inactivated X chromosome during subsequent cell divisions Signup and view all the answers

What is the estimated percentage of X-linked genes in humans that may escape full inactivation?

Up to 25% Signup and view all the answers

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?

Genomic imprinting Signup and view all the answers

Which allele of the Igf2 gene is transcribed into RNA?

Paternal allele Signup and view all the answers

What is the effect of inheriting an Igf2− allele from a male parent?

The mouse will be small in size Signup and view all the answers

What is the term for the phenomenon where only one allele of a gene is expressed, depending on its parental origin?

Monoallelic expression Signup and view all the answers

What is the purpose of genomic imprinting?

To silence the expression of one allele based on its parental origin Signup and view all the answers

What is the role of chromatin in genes that escape X-chromosome inactivation?

To loosen the chromatin and allow gene expression Signup and view all the answers

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.