分子遗传学——人类分子遗传学Human Molecular Genetics I.pptVIP

Human Molecular Genetics Actions of chromosomes during cell division -Mitosis and Meiosis Mitosis: the division of single nucleus into two identical nuclei -occurs in somatic cell -cell growth, cell repair Meiosis: occurs in the reproductive organs of sexually reproducing organisms -produces germ cells ,i.e. sperm and egg Mitosis The form of cell division by which a eukaryotic somatic cell duplicates. Mitosis is asexual reproduction. Cell division is the continuation of life based on the reproduction of cells. Cell Cycle The dividing and non-dividing stages in the life of a cell. Phases: 1. Interphase: growth and DNA replication 2. Prophase 3. Metaphase 4. Anaphase 5. Telophase Cell cycle Metaphase Chromosomes Meiosis The form of cell division by which gametes, with half the number of chromosomes, are produced. Diploid (2n) ? haploid (n) Meiosis is sexual reproduction. Two divisions (meiosis I and meiosis II). X chromosome dosage How to create equal amount of X chromosome gene products in males and females? Shouldn’t XX females produce twice the amount of X-linked gene products (proteins) as XY males? The Lyon Hypothesis The inactive X can either be maternal or paternal in origin and the choice is random in each cell and independent of the choice in other embryonic cells. X inactivation is irreversible in somatic cells - the inactive X in a particular cell remains inactive in all descendents of that cell--cloning. X-inactivation reveals alleles in cats heterozygous for the fur color gene Numbers of sex chromatin are different in individuals with different karyotypes Number of X chromatin = Number of X chromosome－1 Number of Y chromatin = Number of Y chromosome Morphological Types of Human Chromosomes: Karyotype: A chart arranging chromosome pictures according to their size and morphological shapes (centromere location), grouped by pairs of homologous chromosomes. A karyotype is described by first listing the number of chromosomes foll