Life Science Quiz | Applied Genetics, Immunity, Drug Resistance and Human Regulation

A phenotype can be influenced by both genotype and environmental factors. Because the experiment keeps genetic background nearly constant while changing light conditions, the difference shows that environment can affect phenotype. Appearance alone does not establish that the DNA sequence changed or that the observed change will be inherited.

Meiosis produces gametes with one chromosome set from cells that initially have two sets. Fertilization joins two 12-chromosome gametes and restores the total to 24, preventing chromosome number from doubling in each generation. Ordinary mitosis does not halve the number of chromosome sets.

For an Aa by Aa cross, the possible genotypes in each pregnancy are AA, Aa, Aa and aa. The trait-expressing aa genotype therefore has a probability of one quarter. The first child's outcome does not change which gametes combine at the next fertilization. This probability does not guarantee exactly one affected child in every four children within a family.

A variant that arises after conception outside the germ cells and remains in a limited cell lineage is a somatic variant. It can be passed to descendants of that cell, but it is not ordinarily inherited by the next generation if germ cells do not carry it. Somatic variants also do not invariably cause disease; their effects depend on their location and function.

The presence of a normal amount of mature mRNA indicates that transcription from DNA to RNA has occurred. Ribosomes read the mRNA sequence and join amino acids during translation, so failure to bind directly disrupts translation. DNA replication and meiosis are separate from protein synthesis using this mRNA.

Some cells that recognize X remain as memory cells after the primary response. On re-exposure to X, they can proliferate and begin antibody production more rapidly. The slow response to the new antigen Y shows that immune memory is antigen-specific rather than a universal acceleration of responses to every antigen.

Antibiotics target bacterial structures and processes, such as bacterial cell-wall synthesis, so they do not act on the virus itself. Antiviral drugs have different targets. An antibiotic may be used for a bacterial secondary infection accompanying a viral illness, but the question explicitly states that no such infection is present.

The antibiotic reduces susceptible bacteria, while bacteria that already carry resistance are more likely to survive. As those survivors reproduce, the proportion of resistant bacteria increases. Resistance is a property of the microorganisms, not of the human body, and the antibiotic does not cause all bacteria to intentionally generate the needed mutation.

Insulin helps glucose move from the blood into cells, where it can be used for energy. The increased uptake in the insulin-treated group is consistent with this function. Insulin is not made by converting glucose directly into the hormone, and blood-glucose regulation in a whole organism also involves the liver, other hormones and additional factors.

In a nephron, the glomerulus first filters water and small molecules. The tubules then return much of the needed water, minerals and nutrients to the blood, so not all filtered fluid becomes urine. Healthy glomeruli ordinarily retain blood cells and large proteins in the circulation, and reabsorption occurs mainly in the tubules rather than the bladder.