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27.3 Genetic Disorders •Errors in the chromosome number •Genetic Disorders and sex chromosomes •Genetic Disorders and autosomes •Genetic Counseling Errors in Chromosome Numbers • Less than 46 chromosomes • OR • More than 46 chromosomes • Due to mistakes in meiosis • Anaphase, chromosomes do not get pulled appart Errors due to Meiosis 4 Possible Gametes Sperm or Egg *Normal *Normal *Too many *Too few Trisomy • Inheriting three copies of a chromosome instead of two • Too many • 47 chromosomes Down syndrome • Outwardly slanted eyes • Exaggerated fold of skin on the inside of the eye • Flat ears set low on the head • Flattened face • Small teeth • Relatively short arms and legs. Edward syndrome • Defects of the kidneys, ureters, heart, lungs and diaphragm. • Cleft lip or cleft palate. • Small skull (microcephaly). • Malformations of the hands and feet • Neural tube defect, where the spinal cord, meninges and blood vessels protrude through a gap in the vertebrae • Malformations of the sex organs Patau syndrome • Small skull (microcephaly). • An abnormal opening in the skull. • Malformations of part of the brain. • Structural defects of the eyes. • Cleft lip or cleft palate. • Additional toes or fingers • Congenital heart disorders, such as ventricular septal defect. • Neural tube defect, where the spinal cord, meninges and blood vessels protrude through a gap in the vertebrae • Malformations of the sex organs. Monosomy • Inherit one copy of a chromosome instead of two • Too few • 45 chromosomes Monosomy Disorders • Turner Syndrome Turner Syndrome • condition in females (XX) • Due to an absent X-chromosome • short stature • sexual underdevelopment • physical abnormalities Types of Chromosomes 1. Autosome: a non-sex chromosomes pairs 1 -22 on a karyotype 2. Sex chromosomes: the XX or XY pair 23 on a karyotype Genetic Disorders Carried by Sex Chromosomes: • Hemophilia Carried by Autosomes • Dyslexia • PKU Hemophilia • Disorder • Blood can not form clots • Found on recessive gene Dyslexia • A learning disorder • Can not see or write letters and or words • Appear backwards • Dominant gene PKU • Body lacks the enzyme necessary to metabolize phenylalanine to tyrosine. • Causes brain damage and progressive mental retardation Genetic Counseling • Provide information and support to families who have members with birth defects or genetic disorders • Or • to families at risk for a variety of inherited conditions. Counselors • They identify families at risk, investigate the problem present in the family, interpret information about the disorder, analyze inheritance patterns and risks of recurrence, and review available options with the family. Pedigree • a diagram of family relationships that uses symbols to represent people and lines to represent genetic relationships. • Determine the mode of inheritance (dominant, recessive, etc.) of genetic diseases. Pedigree • A series of symbols are used to represent different aspects of a pedigree. Pedigree Dominant traits: • Never skips a generation • Two affected individuals can give rise to unaffected individuals Recessive traits: • may skip a generation • two unaffected individuals can give rise to affected individuals Marriage Line I Children line II Siblings III IV
"27.3 Genetic Disorders"