GCD 3022 1st Edition Lecture 10Outline of Last Lecture I. Introductiona. Maternal effect and epigenetic inheritanceb. Extranuclear inheritanceII. Maternal Effecta. Definitionb. Explanationc. Example: water snailIII. Epigenetic Inheritancea. Definitionb. Explanation of Causesc. Dosage Compensationi. Definitiond. X-inactivationi. Barr body1. Tableii. Lyon hypothesisiii. MechanismOutline of Current Lecture These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.I. Genomic Imprintinga. Definitionb. Three stagesc. Example: Igf-2 in miceII. Imprinting and DNA methylationa. Imprinting of genesb. MethylationIII. Extranuclear Inheritancea. Definitionb. Organellesc. Mitochondriad. ChloroplastsIV. Maternal Inheritancea. Definitionb. The four o’ clock plantc. Cellular explanationCurrent LectureI. Genomic Imprintinga. A segment of DNA is marked and the effect is maintained throughout the life of the organism inheriting the marked DNA. i. Follows a non-Mendelian pattern of inheritanceii. Monoallelic expression: Depending on how the genes are “marked”, the offspring expresses either the maternally-inherited or paternally-inheritedallele (not both)iii. Permanent in the somatic cells of an animal, but marking of alleles can be altered from generation to generationb. Three Stages: imprinting is an epigenetic process at the cellular leveli. Establishment of the imprint during gametogenesisii. Maintenance of the imprint during embryogenesis and in the adult somatic cellsiii. Erasure and reestablishment of the imprint in the germ cellsc. Example: Igf-2 in micei. Igf-2 gene encodes a growth hormone called insulin growth factor 2. A functional Igf-2 gene is necessary for normal size. ii. Imprinting results in the expression of the paternal but not the maternal allele (paternal allele is transcribed into RNA, maternal allele is not transcribed)iii. Igf-2m is a loss-of-function allele that does not express a functional Igf-2 protein (results in dwarfism depending on if the mutant allele was inherited from the father or mother)II. Imprinting and DNA methylationa. Imprinting of genesi. Involves a marking process called methylation. ii. The imprinting of several genes involves an imprinting control center (ICR)located near the imprinted gene, which is methylated in the oocyte or thesperm (not both)iii. The ICR contains binding sites for one or more transcription factors that regulate the imprinted geneb. Methylationi. During gamete formation either the oocyte (egg) or the spermatocyte (sperm) is methylated (not both), this depends on the gene in questionii. If one is methylated it is called de novo methylation and causes an inactivation of transcription from that gamete when it attempts to pass the genetic information on to the offspring iii. Ex: if the sperm is methylated, then the paternal chromosome that is inherited by the offspring will not exhibit the paternal phenotype for that gene (and will exhibit the maternal phenotype)III. Extranuclear Inheritancea. Inheritance patterns inheriting genetic material outside the nucleus (names mitochondria and chloroplasts). Also known as cytoplasmic inheritancei. Genetic material is located in a region called the nucleoid (can contain several copies of the chromosome, and an organelle can contain more than one nucleoid)ii. Genome is composed of a single circular chromosome containing double-stranded DNAb. Mitochondria: organelle of extranuclear inheritance in animalsi. Main function of mitochondria is oxidative phosphorylation to produce ATP (energy) for the cellii. Genetic material in mitochondria is referred to mtDNA (carries relatively few genes, mostly rRNA and tRNA for oxidative phosphorylation)iii. Most mitochondrial proteins are encoded by genes in the nucleus. These proteins are made in the cytoplasm, then transported into the mitochondriac. Chloroplasts: organelle of extranuclear inheritance in plantsi. Main function of chloroplasts is photosynthesisii. Genetic material is referred to as cpDNA (about 10x larger than mitochondrial genome of animal cells)iii. cpDNA carries between 110 and 120 different genes (also tRNA and rRNA genes, polypeptides required for photosynthesis)iv. As with mitochondria, many proteins are encoded by genes in the nucleus. These proteins are made in the cytoplasm and transported into the chloroplastIV. Maternal Inheritancea. Phenotype of the offspring depended solely on the maternal parent and not at allon the paternal parent (different than maternal effect)b. Four o’ clock plant: pigmentation in this plant shows this type of non-Mendelian inheritancei. Discovered by Carl Corrensii. Leaves can be green (wild-type), white (mutant), or variegated (called heteroplasmy) (green/white patches)iii. Phenotype of the leaves can be explained by the types of chloroplasts found in leaf cells. If variegated, the leaf starts out green and turns variegated while maturing due to the irregular distribution to daughter