6 4 Types of Genetic Disorders Single geneChange in the DNA sequenceMore than 6000 known disordersAutosomal or sex linked1 in 200 birthscystic fibrosis, sickle cell anemia, Marfan syndrome, Huntington’s disease
7 Types of Genetic Disorders Multifactoralcombination of environmental factors and mutations in multiple genesmore complicatedheart disease, high blood pressure, Alzheimer’s disease, arthritis, diabetes, cancer, and obesity
8 Types of Genetic Disorders Chromosomalabnormalities in chromosome structure as missing or extra copies or gross breaks and rejoiningDown Syndrome
9 Types of Genetic Disorders Mitochondrialrare type of genetic disordercaused by mutations in the non-chromosomal DNA of mitochondria
10 Dominant genetic disorders On our chromosomes are a total of about 100,000 genes. Among these 100,000 genes, each person has on average 5-8 bad genes. However, these seldom have any effect at all. But sometimes there are serious errors in our genetic code and these can give us the blueprint for genetic disorder. When we have a serious genetic error, there are three primary ways that the error can be inherited (passed from generation to generation). These three patterns of inheritance are:Dominant genetic disordersRecessive genetic disordersSex-linked genetic disordersGenetic DisordersOn our chromosomes are a total of about 100,000 genes. Among these 100,000 genes, each person has on average 5-8 bad genes. However, these seldom have any effect at all. But sometimes there are serious errors in our genetic code and these can give us the blueprint for genetic disorder. When we have a serious genetic error, there are three primary ways that the error can be inherited (passed from generation to generation). These three patterns of inheritance are:Dominant genetic disordersRecessive genetic disordersSex-linked genetic disorders
11 Dominant Genetic Disorders: In the dominant genetic disorder pattern of inheritance, one bad gene from either parent will cause the genetic disorder. Since only one bad gene causes the disorder, if either parent has the disorder the chance of the child inheriting the bad gene and developing the disorder is 50% with each conception.
12 Recessive Genetic Disorders: To develop a recessive genetic disorder both parents must contribute the same defective gene. The parents usually don't have the disorder, but are carriers for the disorder. They carry one defective gene, which is recessive, and one normal dominant gene.
13 Sex-linked Genetic Disorders: These disorders occur due to errors in the 23rd pair of chromosomes (the chromosomes responsible for gender). These genetic disorders occur only in males. Since males have an XY sex chromosome combination, they are vulnerable to defects on their X chromosome that lacks a partner gene on the Y. These disorders do not appear in females (which are XX) because if one of the X chromosomes has an affected gene, the partner X chromosome carries a normal gene. In females, the other X will compensate any defect on one X. Since males get a Y, there is no compensation. Although the female can carry a defective gene, females do not develop the disorder – they are carriers for the disorder.
14 copyright cmassengale Mendelian Genetics4/15/2017Sex-linked TraitsTraits (genes) located on the sex chromosomesSex chromosomes are X and YXX genotype for femalesXY genotype for malesMany sex-linked traits carried on X chromosomecopyright cmassengale
15 copyright cmassengale Mendelian Genetics4/15/2017Sex-linked TraitsExample: Eye color in fruit fliesSex ChromosomesXX chromosome - femaleXy chromosome - malefruit flyeye colorcopyright cmassengale
16 Sex-linked Trait Problem Mendelian GeneticsSex-linked Trait Problem4/15/2017Example: Eye color in fruit flies(red-eyed male) x (white-eyed female) XRY x XrXrRemember: the Y chromosome in males does not carry traits.RR = red eyedRr = red eyedrr = white eyedXY = maleXX = femaleXRXrYcopyright cmassengale
17 Sex-linked Trait Solution: Mendelian Genetics4/15/2017Sex-linked Trait Solution:XRXrY50% red eyed female50% white eyed maleXR XrXr Ycopyright cmassengale
18 Other Genetic Disorders: Other genetic disorders do not fall neatly into one of these three patterns. These involve having too many or too few chromosomes.
19 Turners Syndrome 1 in 5,000 births 45 chromosomes X only #23 Monosomy Nondisjunction
20 Turners Syndrome 96-98% do not survive to birth No menstruation No breast developmentNo hipsBroad shoulders and neck
21 Cri-Du-Chat Syndrome 1 in 216,000 births 46 chromosomes XY or XX #5 Deletion of lower arm
45 Triple X Syndrome 1 in 2,500 births 47 chromosomes XXX only #23 Trisomy Nondisjunction
46 Triple X Syndrome Normally physically Normal mentally Learning disabilitiesTaller than averageBehavior Problems
47 Huntington’s Chromosome 4 mutation. involuntary twitching or movement Huntington’s Chromosome 4 mutation *involuntary twitching or movement *onset 40 yrs. *deterioration of the CNS that affects muscle control
48 Sickle-cell Anemia Moon shaped RBC that has low hemoglobin Shows up more often in African Americans; or whose ancestors once inhabited parts where malaria is a high risk.Sickle-shaped cells clog capillaries so that cells cannot get oxygen and nutritionBlood transfusions, pain killers, and drugsPain, strokes, jaundice.
49 Cystic Fibrosis Chromosome 7 mutation Affects mucus, salivary and sweat glands.Many respiratory problemsThick, sticky mucus in lungs and digestive tracts.
50 Tay-Sachs No Hex A enzyme Recessive genetic disorder most often found in Jewish or eastern Europe origin.Appears in children starting at 6 mo.Child cannot metabolize a certain lipid which incases the CNS and prevents the brain from expanding.Fat builds up in the brain causing blindness & paralysisDeath occurs in early childhood
51 Hemophilia Blood has less than 1% of the normal clotting factor Bleeds longer because blood won’t clot.
52 Color-blindness Cones in the eye do not perceive certain colors Most common form is reds/greens but some are brown/blueSeen as gray
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