Title: Genetic Diseases
1Autosomal recessive genetic diseases (disorders) aAutosomal means the defective gene is carried on one of the first 22 chromosomes (the autosomal chromosomes) and not on the sex chromosomes (#23) bIf you have one copy of the gene you are a carrier for the disease, but do not have the disease cIf you have two copies of the defective gene you have the disease deSome common autosomal recessive disorders are
1Cystic fibrosis – the most commonly inherited genetic disorder among
Caucasian people
2Sickle cell anemia – the most common genetic disorder among black people
3Albinism is an autosomal recessive disorder that in seen in all races of people and all species of animal
4Phenylketonuria is an autosomal recessive disorder hat every newborn in the United States is tested for
5The “Jewish Genetic Disorders” These diseases are most common among people of Ashkenazi origin. These diseases include: Tay-Sachs.
Niemann-Pick, Canavan’s Disorder, Bloom’s Disease, Familial
Dysautonomia and Fanconi Anemia fProblems aA Man with sickle cell anemia has woman with a children who is homozygous normal. What are the chances they will produce a child who is a carrier for this condition?

bIf one of the children in the above question has children with a partner who is heterozygous for this condition what will the genotypes and phenotypes of these children be?
2Autosomal Dominant Genetic Disorders aThere are no carriers for these diseases. If you have one copy of this gene then you HAVE the disease. bThese diseases are often fatal and people do not live long enough to pass the gene on by having children. However, this is not always true cHuntington’s Chorea (disease) and polydactyl (extra fingers and toes),
Marfan’s syndrome and are examples of this type of inheritance. dProblems
1A man who is heterozygous for Huntington’s has children with a woman with the homozygous recessive genotype. What percentage of their children will have Huntington’s disorder. What percentage of their children will be healthy?
2Two people both heterozygous for polydactyl have children. What percentage of their children will have the normal number of fingers and toes? One of their children who is homozygous dominant for the trait has children with a woman who has the recessive phenotype.
How many of their children will have the dominant genotype. How many will have the dominant phenotype?
3- Sex-Linked (or X-linked) genetic disorders aX-linked genetic disorders are carried on the X chromosome bThe X chromosome is one of the two sex chromosomes cSex – linked genetic disorders are passed from mother to son. dWomen are carriers of the disease – They DO NOT have it, but with each pregnancy they have a 50-50 chance of passing it on to their sons eBoys are not carriers – If they have the gene they have the disease

fExamples of x-linked disorders are hemophilia (The Royal Disease of
Europe), color blindness, Duchenne’s Muscular Dystrophy and
Adrenoleukodystrophy (ALD) gIt is possible for a woman to get one of these diseases, but only if the woman is a carrier for the disease and the man has the disease. Most of these diseases are fatal for young boys so they do not live long enough to have children. Therefore it is rare for woman to have these diseases. hEXAMPLE iProblems aA woman who is a carrier for the colorblind gene has children with a man who is colorblind. What percentage of their sons will be color blind? Will any of their daughters be colorblind? bA woman who inherited the gene for hemophilia from her mother has children with a man who does not have hemophilia. Using a Punnet square show all the possible genotypes of their children. How would we describe their phenotypes? cUse the information in question b. Assume modern medicine enables one of her sons with hemophilia to have children with a healthy, noncarrier female. Will any of their children have hemophilia? Will any of the children be carriers?