Contemporary Issues in Biology: Lecture 8 Questions and Answers

Contemporary Issues in Biology: Lecture 8 Questions and Answers how are chromosomal abnormalities developed - Answer- caused by problems with meiosis --> gametes have abnormal numbers of chromosomes (too many or too few) or structural abnormalities (portion of the chromosome could be missing or duplicated) --> if fertilization occurs and the embryo survives, the chromosomal abnormality is present in all the cells chromosomal disorders as a result of chromosomal abnormalities - Answer- when chromosomal abnormalities occur they are typically lethal (because important genes are usually missing); as a result, embryos will fail to develop; some chromosome abnormalities are not lethal but they are associated with serious human disorders characteristics of child with down syndrome - Answer- wide, rounded face; intellectually disabled; enlarged tongue, making speech difficult amniocentesis - Answer- recommended for pregnant women over 35 years of age; performed during weeks 15-17 of pregnancy; a needle is inserted into the amniotic sac, and amniotic fluid with fetal cells is removed; a karyotype of the fetal chromosomes is prepared risk of having child with down syndrome versus risk of miscarriage due to amniocentesis - Answer- before age 45, risk of a miscarriage due to an amniocentesis is higher than the risk of the baby having down syndrome; after age 45, with the risk of down syndrome being higher than miscarriage, the test is more common example of a genetic disease caused by a single gene - Answer- cystic fibrosis: life- threatening disorder; damages lungs and also digestive system; mucous and other body fluids are thick and sticky; caused by a recessive allele important point about inheritance - Answer- genes have different forms, called alleles; each trait is controlled by effects of two alleles to two chromosomes; some alleles are dominant/recessive and other alleles are co-dominant a women with normal lung physiology has a child with a man who has normal lung physiology, but are both carriers of the allele. what is the chance that the child will have cystic fibrosis? - Answer- 25% hemophilia - Answer- caused by a sex-linked recessive allele where a person lacks the blood proteins for clotting; genetics and human diseases - Answer- about 4,000 human diseases are thought to be inherited; scientists are making progress figuring out where genes are located on chromosomes and in understanding how the mutations in genes cause disease; most diseases are likely controlled by the action of more than one gene; most diseases are effected by the environment as well as genes; the implication is that the presence of one allele does not indicate that you will develop a disease