Imprinted genes:

Question

Imprinted genes:

BlackTom AI · Accepted Answer

Imprinted genes are regulated by parent-of-origin-specific epigenetic marks, so they provide a clear example of epigenetic inheritance and are controlled by differentially methylated regions.

1. Relevant knowledge points and concepts
- Genomic imprinting: certain genes are expressed monoallelically depending on whether the allele came from the mother or father.
- Epigenetic inheritance: transmission of gene-expression patterns through mechanisms other than DNA sequence changes (e.g., DNA methylation, histone modifications).
- Differentially methylated regions (DMRs) / imprinting control regions (ICRs): DNA segments that carry parent-specific methylation patterns and control imprinting of nearby genes (e.g., IGF2/H19 locus).

2. Step-by-step reasoning
Step 1: Imprinting results in one allele being active and the other silent based on parental origin. This is not due to change in the DNA sequence but due to reversible chemical marks. 
Step 2: Those chemical marks are typically DNA methylation at CpG sites and associated chromatin states applied in the germline and maintained through development. 
Step 3: The methylation patterns that differ between parental alleles are precisely what we call DMRs or ICRs; these regions lie adjacent to or within imprinted genes and regulate their expression.
Step 4: Because imprinting depends on epigenetic marks rather than sequence, it is an example of epigenetic inheritance.

3. Calculations / intermediate steps
- No numerical calculations are required. Logical intermediate steps are given above to link imprinting → epigenetic marks → DMRs.

4. Why the correct answer is correct
- A is correct: imprinted genes are a prototypical example of epigenetic inheritance because parental-specific methylation determines allele expression without changing DNA sequence.
- B is correct: imprinted genes are associated with DMRs (imprinting control regions) that show parent-specific methylation patterns and regulate nearby imprinted loci.

5. Why other options are incorrect
- C (“Are only transmitted by one parent”) is incorrect: both parents transmit their alleles to offspring. Imprinting affects which parental allele is expressed, not which allele is transmitted. 
- E (“None of the above”) is incorrect because A and B are true.

6. Conclusion and answer confirmation
Therefore the correct choice is A and B (option D in the list). This matches the provided answer: A and B.

Imprinted genes:单项选择题

类似问题

The expression of a single allele is associated with which of the following?

The Igf2 gene is expressed from the paternal parent but not from the maternal parent. An ICR is located between the H19 and Igf2 genes. If a mutation eliminated this ICR, how would it affect the expression of the Igf2 gene?

Genomic imprinting is an example of epigenetic inheritance.

Imprinted genes:

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