AP Bio Ch 13 Human Genetics Quiz

Karyotyping is a technique used to analyze the number and structure of chromosomes in a person's cells. In prenatal diagnosis, karyotyping can be used to determine if the fetus has a normal chromosome number and structure. By examining the chromosomes, any abnormalities or genetic disorders can be detected. Therefore, the statement that karyotyping can be used to tell whether the chromosome number and structure are normal in prenatal diagnosis is true.

Duchenne muscular dystrophy is a genetic disorder characterized by the absence of the protein dystrophin in muscle tissue. This protein is essential for maintaining the structure and function of muscle cells. Without dystrophin, muscle fibers become weak and eventually die, leading to progressive muscle weakness and loss of mobility. Therefore, it is true that Duchenne muscular dystrophy is caused by the lack of the protein dystrophin in affected muscle tissue.

Sickle-cell disease is the correct answer because it is a genetic disorder that causes red blood cells to become deformed and take on a sickle shape. This abnormal shape makes it difficult for the cells to flow through blood vessels, leading to poor circulation and anemia. Male pattern baldness, Huntington disease, hemophilia, and Duchenne muscular dystrophy are unrelated to the symptoms described.

If the parents are AO and BO genotypes for the ABO blood group, their children could include AO, BO, AB, and OO only. This is because the parents have both the A and B alleles, and they can pass either one of these alleles to their children. Therefore, their children could inherit the A allele from one parent and the O allele from the other parent, resulting in the AO genotype. Similarly, they could inherit the B allele from one parent and the O allele from the other parent, resulting in the BO genotype. Additionally, there is a possibility of inheriting both the A and B alleles, resulting in the AB genotype. Finally, there is also a possibility of inheriting two O alleles, resulting in the OO genotype.

In a pedigree chart, a line between a circle and a square represents a mating. This means that the circle and square are the parents who have produced offspring. The circle represents a male, and the square represents a female, as indicated by the given information. The line connecting them symbolizes their union or mating. The chart uses different shapes and symbols to represent different individuals and their relationships, allowing for a visual representation of the genetic inheritance patterns in a family.

During meiosis, homologous chromosomes are supposed to separate, but when they fail to do so, it is called nondisjunction. This can result in an abnormal number of chromosomes in the resulting gametes, which can lead to genetic disorders such as Down syndrome. Cross-over refers to the exchange of genetic material between homologous chromosomes, RFLP is a technique used in genetics research, and linked genes are genes that are located close together on the same chromosome and tend to be inherited together.

Hemophilia is a genetic disorder that is associated with the inability to produce factor VIII in the blood. Factor VIII is a protein that helps in the clotting of blood. Individuals with hemophilia have a deficiency or absence of this protein, which leads to prolonged bleeding and difficulty in clotting. This condition is more commonly found in males, as it is an X-linked recessive disorder.

Rh is not an allele of the ABO blood group. The ABO blood group system is determined by the presence or absence of antigens A and B on the surface of red blood cells, while the Rh blood group system is determined by the presence or absence of the Rh antigen. These two blood group systems are independent of each other and are inherited separately. Therefore, the statement that Rh is an allele of the ABO blood group is false.

Sickle-cell disease provides protection against malaria in the heterozygote. This is because individuals who are heterozygous for the sickle-cell gene have a higher resistance to malaria infection compared to those who do not carry the gene. The presence of the sickle-cell gene alters the shape of red blood cells, making it more difficult for the malaria parasite to invade and replicate within the cells. Therefore, individuals with sickle-cell trait have a survival advantage in regions where malaria is prevalent.

A karyotype is a visual representation of an individual's chromosomes, arranged in pairs according to size and shape. The chromosomes are not numbered from smallest to largest in a karyotype; instead, they are usually organized in pairs based on their size, with the largest pair being the first and the smallest pair being the last. Therefore, the statement that "chromosome pairs are numbered from smallest to largest" is not true about a karyotype.

Fragile-X syndrome is caused by the repeats of base triplets, specifically CGG, on the X chromosome. This genetic disorder results in the inactivation of the FMR1 gene, which is responsible for producing a protein that is important for brain development and function. The excessive repeats of CGG cause the X chromosome to become fragile and susceptible to breakage, leading to the characteristic symptoms of fragile-X syndrome, such as intellectual disability, behavioral and learning challenges, and physical features like a long face and large ears. Unlike the other syndromes listed, which are caused by abnormalities in whole chromosomes, fragile-X syndrome is specifically caused by the repeat expansion in a single gene.