GENETICS AND GENETICALLY LINKED DISEASES Chapter 22

© Copyright 2004 Delmar Learning, a division of Thomson Learning, Inc.2 GENETICS Genetics is the branch of biology that studies how genes are transmitted from parent to offspring

© Copyright 2004 Delmar Learning, a division of Thomson Learning, Inc.3 TYPES OF MUTATIONS There are two types of mutations –Gene mutation - a new or altered gene is produced to replace a normal, preexisting gene –Chromosomal mutation - involves a change in the number of chromosomes in the nucleus or a change in the structure of a whole chromosome

© Copyright 2004 Delmar Learning, a division of Thomson Learning, Inc.4 TYPES OF MUTATIONS Somatic cell mutation - mutations that occur in individual body (somatic) cells will not be transmitted to the offspring Gametic cell mutation - mutations that occur in the gametes that will be passed on to the next generation

© Copyright 2004 Delmar Learning, a division of Thomson Learning, Inc.5 LETHAL GENES Lethal genes are those genes that usually end in death Each person carries two or three recessive lethal genes Two similar recessive genes must be present for the lethal gene to be expressed

© Copyright 2004 Delmar Learning, a division of Thomson Learning, Inc.6 HUMAN GENETIC DISORDERS Phenylketonuria Sickle cell anemia Tay-sachs disease Duchenne’s muscular dystrophy Huntington’s disease Cystic Fibrosis Thalassemia

© Copyright 2004 Delmar Learning, a division of Thomson Learning, Inc.7 HUMAN GENETIC DISORDERS Hemophilia Chromosomal Aberrations Mutagenic Agents

© Copyright 2004 Delmar Learning, a division of Thomson Learning, Inc.8 GENETIC COUNSELING Genetic counseling involves screening for potential genetic disorders by talking with prospective parents about the possibility of genetic disorders