* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Chapter 14: Human Inheritance
Skewed X-inactivation wikipedia , lookup
Biology and consumer behaviour wikipedia , lookup
Genetic drift wikipedia , lookup
Gene therapy of the human retina wikipedia , lookup
Genomic imprinting wikipedia , lookup
Vectors in gene therapy wikipedia , lookup
Polycomb Group Proteins and Cancer wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Epigenetics of human development wikipedia , lookup
Public health genomics wikipedia , lookup
Point mutation wikipedia , lookup
Medical genetics wikipedia , lookup
Designer baby wikipedia , lookup
Neuronal ceroid lipofuscinosis wikipedia , lookup
Epigenetics of neurodegenerative diseases wikipedia , lookup
Microevolution wikipedia , lookup
X-inactivation wikipedia , lookup
Genome (book) wikipedia , lookup
Section 14-2: Human Genetic Disorders From Molecule to Phenotype There is a direct link between genotype and phenotype Example: People of African or European descent are more likely to have wet earwax (dominant) while those of Asian or Native American ancestry have the dry form (recessive) The difference is in ONE BASE in the gene for a membrane-transport protein - a change from a G to an A Changes in a gene’s DNA sequence can change proteins by altering their amino acid sequences, which may directly affect one’s phenotype Disorders Caused by Individual Genes Sickle Cell Disease Caused by defective allele for beta-globin, part of hemoglobin Makes hemoglobin less soluble, molecules stick together when blood’s oxygen level decreases Molecules clump into long fibers, forcing cells into a sickle shape that are more rigid than normal RBCs, and they Tend to get stuck in the capillaries Can result in damage to cells, tissues, organs Disorders Caused by Individual Genes Cystic fibrosis (CF) Most common among people of European ancestry Most cases result from the deletion of just 3 bases in the gene for a protein called cystic fibrosis transmembrane conductance regulator (CFTR) Amino acid phenylalanine is missing from the protein CFTR normally allows chloride ions (Cl−) to pass across cell membranes - the removal of phenylalanine causes the protein to misfold, and it is destroyed Disorders Caused by Individual Genes CF con’t Tissues malfunction because cell membranes can’t transport Cl Children with CF have serious digestive problems and produce thick, heavy mucus that clogs their lungs and breathing passageways People with one normal copy of the CF allele are unaffected by CF, because they can produce enough CFTR to allow their cells to work properly Two copies of the defective allele are needed to produce the disorder – it is recessive Disorders Caused by Individual Genes Huntington’s disease Caused by a dominant allele for a protein found in brain cells Allele contains a long string of bases in which the codon CAG (glutamine) repeats over and over again – more than 40X Reason why is unknown Symptoms of Huntington’s disease do not appear until middle age - mental deterioration and uncontrollable movements The greater the number of codon repeats, the earlier the disease appears, and the more severe are its symptoms Genetic Advantages Why are alleles for sickle cell disease or CF still around if they can be fatal for those who carry them? Individuals with one sickle cell allele are resistant to malaria Individuals with one CF allele have a harder time developing typhoid fever Chromosomal Disorders Usually caused by nondisjunction Creates gametes with an abnormal number of chromosomes Chromosomal Disorders If 2 copies of an autosome do not separate, a person can be born with 3 copies of that chromosome – known as trisomy The most common form of trisomy is Down syndrome (trisomy 21) Mild to severe mental retardation and a high frequency of certain birth defects Chromosomal Disorders Nondisjunction of X chromosomes can lead to Turner’s syndrome, where a woman only inherits one X chromosome Called a monosomy Sex organs do not develop properly at puberty, sterile, small/short stature, high voice Karyotype: 45, XO Chromosomal Disorders Nondisjunction can also cause a male to inherit an extra X chromosome Disorder called Klinefelter’s syndrome Also sterile Karyotype: 47, XXY