Download
1 / 13
160 likes | 279 Views
Genetic Disorders. Review. Parents pass traits to their offspring through their genes . Genes are located on bigger structures called chromosomes ; each person has 46 of these, which are joined into 23 pairs . Each parent contributes one-half of each pair.
E N D
Review • Parents pass traits to their offspring through their genes. • Genes are located on bigger structures called chromosomes; each person has 46 of these, which are joined into 23 pairs. • Each parent contributes one-half of each pair. • It's how those genes work together that makes you unique!
Diseases • Scientists have discovered that some medical disorders are genetic. • Problems arise when the disease gene is dominant or when the same recessive disease gene is present on both chromosomes in a pair.
If a person carries the dominant gene for a disease, he or she will usually have the disease • Diseases caused by a dominant gene include: • Marfan syndrome (a connective tissue disorder). People with Marfan have an increased risk that their aorta will enlarge and eventually rupture. • Huntington disease (a degenerative disease of the nervous system).
People who have one recessive gene for a disease are called carriers, and they don't usually have the disease because they have one normal, dominant gene. In other words, their genotype for this trait is heterozygous. However, when two carriers have a child together the child has a 1 in 4 (25%) chance of getting the disease gene from both parents, which results in the child having the disease. Carriers
Examples of Recessive Disorders • Disorders that occur when recessive disease genes from both parents come together in a child. (homozygous recessive) • Cystic fibrosis (a lung disease) • Sickle cell anemia (a blood disease) • Tay-Sachs disease (which causes nervous system problems)
If both parents are carriers (heterozygous) what is the probability that they will pass this recessive gene to their child? Complete a Punnett Square to model the probabilities. N =normal red blood cell n =sickle cell.
X-linked Genetic Disorders • You have 23 pairs of genes and one of the pairs determines what gender you are: male or female Boys: XY Girls: XX • Some recessive genes are carried only on the X chromosome, which means that usually only males can develop the disease because they have only one X chromosome. • Females have two X chromosomes, so they would need to inherit two copies of the recessive gene to get the disease.
X-linked disorders • X-linked disorders include color blindness and the bleeding disorder hemophilia. • Hemophilia is a genetic disorder in which a person's blood does not clot properly. • A person who has hemophilia has a tendency to bleed excessively. • The Royal Courts of Europe provide an interesting case study of hemophilia in a family tree.
The “Royal Disease” • Normally, hemophilia is quite rare. • But because royal families usually married people from other royal families, there was more of a chance that children would inherit the gene for this trait. • Queen Victoria of England (1837-1901) was a carrier of the hemophilia gene and subsequently passed the disease on to several royal families.
Two of Queen Victoria's daughters, Alice and Beatrice, were carriers of hemophilia. • They passed the disease on to the Spanish, German and Russian royal families, ensuring that the disease would be present in future generations.
Genetic Mutation • Some genetic disorders are caused by mutations in genes. • Brainpop! Genetic Mutation
