LIFE 102 Lecture Notes - Genomic Imprinting, Organelle, Gamete
Document Summary
For a few mammalian traits, the phenotype depends on which parent passed along the allele for those traits. Such variation in phenotype is called genomic imprinting. Genomic imprinting involves the silencing of certain genes that are stamped with an imprint during gamete production. It appears that imprinting is the result of the methylation (addition of ch3) of dna. Genomic imprinting is thought to affect only a small fraction of mammalian genes. Most imprinted genes are critical for embryonic development. Extranuclear genes (or cytoplasmic genes) are genes found in organelles in the cytoplasm. Mitochondria, chloroplasts, and other plant plastids carry small circular dna molecules. Extranuclear genes are inherited maternally because the zygote"s cytoplasm comes from the egg. The first evidence of extranuclear genes came from studies on the inheritance of yellow or white patches on leaves of an otherwise green plant.
