Biology Test 313

Transgenic animals, such as cows, have been genetically modified to produce human proteins in their milk. This technology is used for producing biological products like human protein (α-1-antitrypsin), which is used in treating diseases such as emphysema. The reason correctly explains the assertion, making option A the correct choice.

Gene therapy does involve the insertion of normal genes into an individual's cells to treat or prevent disease, making the assertion true. The reason is also true; however, it's important to note that while gene therapy has the potential to permanently cure genetic disorders, this outcome is not guaranteed for all diseases or all patients. Thus, R is not the correct explanation of A.

The assertion is true; Bt crops are genetically modified to produce an insecticidal protein that provides resistance against specific pests. However, the reason is false because Bt crops actually require fewer chemical pesticides than non-GM crops, as the plants themselves can protect against pests.

Somatic hybridisation does involve the fusion of protoplasts from two different plant species, and the primary aim is indeed to combine desirable traits from both plants into a single new plant. This makes both the assertion and the reason true, with the reason correctly explaining the assertion.

The principle of segregation states that each allele in a pair separates into different gametes during gamete formation. This means that each sex cell (gamete) receives only one allele of each gene. This principle explains how offspring can inherit one allele from each parent for a given trait. An interesting fact is that Mendel derived this principle from his monohybrid cross experiments, laying the groundwork for understanding how traits are transmitted from parents to offspring.

A test cross is used to determine the genotypic makeup of an organism with a dominant phenotype. By crossing the organism in question with a homozygous recessive individual, the phenotypes of the offspring can reveal whether the parent is homozygous dominant or heterozygous. This is a critical tool in genetics for understanding the genetic composition of individuals. An interesting fact is that the test cross is a fundamental genetic technique that has been used since Mendel's time to explore gene segregation and dominance.

Hemophilia is an example of a sex-linked disorder, specifically linked to the X chromosome. It is a condition where blood does not clot properly, leading to excessive bleeding from even minor injuries. Since the gene for hemophilia is located on the X chromosome, it predominantly affects males, who have only one X chromosome. An interesting fact is that females can be carriers of hemophilia but are rarely affected by the condition due to having two X chromosomes, one of which usually carries a normal allele.

Bt toxin, derived from Bacillus thuringiensis, provides resistance against specific insect pests in genetically modified (GM) crops. When insects ingest plant tissues expressing Bt toxin, the toxin binds to receptors in their gut, causing cell lysis and eventually death. This allows farmers to reduce the use of chemical pesticides, leading to more sustainable agricultural practices and protecting the crops from damage by pests such as the cotton bollworm and corn borer.

PCR is indeed used to amplify small segments of DNA, making it possible to have enough DNA for various analyses. One significant application of PCR is in the early detection of diseases by identifying the genetic material of pathogens, even when they are present in very low quantities. Thus, the reason correctly explains the assertion.

The assertion is true as genetically modified crops can indeed help reduce the reliance on chemical pesticides. This is because many GM crops are engineered to have built-in resistance to pests and diseases, as stated in the reason. Therefore, the reason correctly explains the assertion.