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Imprinting - Gene Expression In Imprinted And Nonimprinted Genes, Timing And Mechanism Of Imprinting, Example Of Imprinting: The Igf2 Gene

human found dna

Imprinting refers to the chemical modification of the DNA in some genes that affects how or whether those genes are expressed. One particular kind of DNA imprinting found in mammals is known as parental genomic imprinting, in which the sex of the parent from whom a gene is inherited determines how the gene is modified. While imprinting has been found in only about fifty human genes to date, some estimates suggest it may occur in several hundred more, in perhaps up to 1 percent of all genes. Imprinting defects are responsible for several human diseases, including some forms of cancer. Imprinting also occurs in other organisms, from yeast to plants to fruit flies.

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Imprinting - Gene Expression In Imprinted And Nonimprinted Genes

Chromosomes, and the genes they contain, are inherited in pairs, with one copy of each supplied from each parent. For most genes, both members of the pair, called the maternal and paternal alleles, are used equally. Both are expressed (read by the transcription machinery to make protein) in roughly equal amounts. In contrast, for most imprinted genes, only one allele is expressed, while the other …

Imprinting - Timing And Mechanism Of Imprinting

Although the details of imprinting are still unknown, it is clear that imprinting must occur either during the formation of the gametes or immediately after fertilization, while the two chromosome sets are still distinct. The imprint must be reliably passed on to each new daughter chromosome during DNA replication. The exact molecular mechanism of imprinting is also unknown, but it is thought to i…

Imprinting - Example Of Imprinting: The Igf2 Gene

One of the best-studied imprinted genes is the one that encodes an insulin-like growth factor called growth factor 2 (IGF2). In this gene, the paternal copy is active, whereas the maternal copy is inactive. Imagine that two parents have produced a female child. During egg formation in the mother (or shortly after fertilization), the mother's copy of the IGF2 gene is methylated, rendering it…

Imprinting - Uniparental Disomy And Human Disease

Inheritance of two copies of one parent's chromosome (or part of it) is called uniparental disomy, a type of chromosome aberration. Detection of uni-parental disomy in individuals with genetic disorders was one of the first clues that imprinting had important developmental and medical consequences. Prader-Willi syndrome and Angelman syndrome can both be caused by uniparental disomy of chrom…

Imprinting - Why Imprint?

The evolutionary reason for imprinting is not yet clear, although some scientists propose that, at least in mammals, it arose from an evolutionary tug of war between males and females. In this scheme, fathers (who contribute only sperm) benefit when the embryo grows as fast as possible. Thus, silencing genes that slow down embryonic growth is in their interest, even if it depletes resources from …

In Situ Hybridization - Application Of The Probe For Dna Or Rna To Tissues Or Cells, Conditions That Promote Optimal In Situ Hybridization [next] [back] Immune System Genetics - Overview Of The Immune System, The Puzzle Of Antibody Diversity, Antibody Structure, Gene Segments Combine Randomly To Generate Diversity

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