midterm review - Early in development, one X chromosome is...

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Unformatted text preview: Early in development, one X chromosome is inactivated in each cell - the process is random, it is equally likely that the maternal or paternal X chromosome will be inactivated. All descendent cells maintain the inactivation pattern. Females that are heterozygous for X-linked traits are genetic mosaics. All descendent cells are expressing the b phenotype = white fur All descendent cells are expressing the b phenotype = white fur How does methylation inhibit transcription? Two ways: 1) How does methylation inhibit transcription? 2) Case study: Genomic imprinting Genomic imprinting: the expression of genes is determined by whether the gene is inherited from the mother or the father. This is an example of an inherited form of DNA modification that alters gene expression = epigenetics. Observation: Igf2 = insulin-like growth factor • mice inheriting a deletion of this gene from their father were small (60% of normal birth weight) • mice inheriting the deletion from their mother were normal H19 (functional RNA) is expressed only from maternally- inherited chromosome Igf2 (insulin- like growth factor) is expressed only from paternally- inherited chromosome Insulator: regulatory element that blocks enhancers Experiments with transmission of Igf2 deletion showed mice inheriting deletion from the father were small. Mice inheriting deletion from mother were normal....
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This note was uploaded on 11/26/2011 for the course BIOLOGY 2c03 taught by Professor Dej during the Spring '11 term at McMaster University.

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midterm review - Early in development, one X chromosome is...

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