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Chapter Slides - Cell Reproduction and Genetic Disorders...

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Unformatted text preview: Cell Reproduction and Genetic Disorders NURS 216 Spring 2010 Sabra Smith, MS, RN Objectives Objectives • Review cell division and understand mitosis vs. meiosis • Understand different types of genetic traits and inheritance patterns • Understand aneuploidy and sequelae • Understand effects of teratogens and mutations Chromosomes Chromosomes • Structures in the nucleus of cell containing genetic material in the form of DNA DNA contains genes • Chromosomes Chromosomes • Humans have 22 pairs of autosomal chromosomes and one pair of sex chromosomes (XX or XY) in each cell (diploid cells) • 23 total pairs Human Genetics Human Genetics • Genes­ sections of DNA, are the biological unit of inheritance and contain information needed for cellular function • Alleles – alternate forms of a gene • DNA­ the carrier of genetic material – less likely to have errors • RNA­ single strand helps translate genetic code into enzymes and proteins – more likely to have errors (viruses) DNA RNA amino acids (protein) Two types of cell division: Two types of cell division: • Mitosis • Meiosis – Forms a daughter cell with 23 pairs of chromosomes (regular body cell turnover, tissue growth, etc.) – Forms a gamete (sperm or ovum) with only 23 single chromosomes Mitosis = Cell Proliferation Mitosis = Cell Proliferation • The process by which cells divide and reproduce • Cell division : – Replaces cells of limited lifespan (skin,blood) – Increases tissue mass during growth – Provides tissue repair and wound healing Stages Stages of Mitosis Interphase occurs before mitosis begins: this is when the chromosomes are copied Meiosis Meiosis • Process by which cells halve their number of chromosomes to create gametes, or haploid cells • Each diploid parent cell produces 4 “daughter” or haploid cells • A male and female haploid cell (ovum and sperm) can then fuse to create one diploid cell (zygote) • A zygote then grows into a fetus through rapid MITOSIS After the end of meiosis, the cells split again WITHOUT replicating the chromosomes, creating four cells with only one copy of each Differentiation Differentiation • The process by which proliferating cells are • • • transformed into different and more specialized cell types. The more specialized the cell becomes, the more likely it loses its ability for mitosis. Neurons­ (the most highly specialized cells) often will eventually lose their ability to divide and reproduce Stem cell – a type of cell that remains incompletely differentiated throughout life – On reserve until there is a need for replenishment Homozygotes Homozygotes • People in whom the two alleles of a given pair are the same – AA or aa Heterozygotes • People in whom the two alleles of a given pair are different ­ Aa Dominant Traits Dominant Traits • A dominant gene is given the capital letter • A dominant trait is expressed in either a homozygous or heterozygous pairing (AA or Aa) Recessive Trait Recessive Trait • Recessive genes are given the small letter • A recessive trait is expressed ONLY in a homozygous pairing (aa) Carrier Carrier • A person who is heterozygous for the trait, but does not manifest the trait. • Aa • Examples: Sickle cell carrier, CF carriers • Which types of traits can have carriers?? Autosomal Dominant Disorders Autosomal Dominant Disorders • Transmission of a mutant autosomal – AA or Aa dominant gene on an autosome causes a characteristic to be expressed. frequency. • Males and females are affected with equal Autosomal Dominant Disorders Autosomal Dominant Disorders • • • • • • Achondroplasia Adult Polycystic Kidney Disease Huntington’s Disease Famililial Hypercholesterolemia Marfan’s Syndrome Neurofibromatosis Marfan’s Syndrome Marfan’s Syndrome Autosomal Recessive Autosomal Recessive Disorders • Transmission of a mutant autosomal recessive gene on an autosome results in a disorder only when the recessive gene is inherited from both parents. – aa • Males and females are affected with equal frequency • Examples: colorblindness, CF, sickle cell Sex­Linked Chromosome Sex­Linked Chromosome Disorders • Sex­linked disorders are associated with a recessive mutant gene on the female chromosome (X). • Male Offspring (XY) • Female Offspring (XX) – very rarely affected – affected X­Linked Recessive Inheritance X­Linked Recessive Inheritance • The recessive gene on the X chromosome • • • • is not offset by a dominant allele on the Y chromosome. Males will express the characteristic. Females do not express the characteristic unless they are homozygous Females may be carriers Ex. Color blindness, Hemophilia A X­Linked Recessive Inheritance X­Linked Recessive Inheritance Alteration in Chromosome Alteration in Chromosome Number (Aneuploidy) • Monosomy • Trisomy – only one member of a chromosome pair – three chromosomes of a chromosome pair – multiple chromosomes of a chromosome pair • Polysomy Trisomy 21 Trisomy 21 (Down’s syndrome) • • • • • • Most common form of chromosome abnormality 1 out of 800­1000 births Varying degrees of mental retardation Incidence greater in mothers older than 35 Nondisjunction­ error in cell division during meiosis, resulting in abnormal number of chromosomes in daughter cells May be related to aging of the oocyte Trisomy 21 (Down’s Syndrome) Trisomy 21 (Down’s Syndrome) • Characteristics – small, rather square head – epicantheal folds – upward slanting eyes – small, malformed ears – open mouth – large protruding tongue – short stubby fingers that curl inward – palmar crease (simean crease) Causes of Alterations in Causes of Alterations in Chromosome Structure • • • • radiation chemicals changes in cellular environment viral infections – varicella – rubella Teratogens Teratogens • A teratogen is an agent that produces – radiation – Drugs (ETOH, cocaine, tetracycline) – chemicals – infectious agents (cytomegalovirus) abnormalities during embryonic or fetal development Fetal Alcohol Syndrome Fetal Alcohol Syndrome • Results from maternal alcohol • • • • consumption Wide variation of effects binge drinking likely has greater effect Estimated 1 in 1000 births in US Causes physical, behavioral, and cognitive abnormalities – Developmental delays – Behavioral dysfunction – Skull/brain malformation – Characteristic facial features Gene Mutations Gene Mutations • • • • • Accidents do happen Errors in duplication of DNA occur Errors are called mutations Mutations may occur spontaneously Mutations may be caused by environmental agents, chemicals, and radiation Gene Mutations Gene Mutations • Gene mutations may occur in either somatic cells (after fertilization) or in germ cells (before fertilization) • Cancer arises from a mutation in the DNA of a somatic cell somewhere in the body which causes uncontrolled replication ...
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This note was uploaded on 02/15/2011 for the course NURS 216 taught by Professor Smith during the Spring '10 term at South Carolina.

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