Two nucleotides are shown in the image. Which of the following best explains what makes these two nucleotides different from each other?

• The nitrogenous base

• The phosphate

• The sugar

• The hydrogen bonds

The enzyme lactase will affect the breakdown of the carbohydrate lactose, but not the carbohydrate starch. The ability of an enzyme to interact with only specific molecules is most directly determined by the-

• Speed of the reaction.

• Structure of the active site.

• Number of molecules involved.

• Temperature of the solution

Differences in heritable (genetic) traits between individuals, such as eye color, are largely determined by differences in--

• The type of sugar in DNA

• The sequence of nucleotides in DNA

• The location of the deoxyribose in DNA

• The number of phosphate groups in DNA

Adenosine deaminase deficiency is a disorder caused by a mutation in a gene on chromosome 20. The gene codes for the enzyme adenosine deaminase (ADA). Without this enzyme, the body is unable to break down the molecule deoxyadenosine. Which of the following best explains how ADA works?

• ADA breaks down into two substrates that react with deoxyadenosine

• ADA is a product of the reaction of deoxyadenosine in the body

• ADA combines with deoxyadenosine to create a new molecule

• ADA speeds up the reaction that breaks down deoxyadenosine into two smaller molecules

A medical test indicates that a patient has a non-functional (does not work) protein. This condition is most likely due to a change in the directions coded in the-

• Sequence of DNA subunits.

• Sequence of inorganic molecules.

• Peptide bonds between amino acids.

• Number of hydrogen bonds in starch molecules.

A student created a model of DNA, which is shown to the right. This student’s model is inaccurate because-

• There must be an equal number of As and Gs.

• The bases are not paired up accurately.

• There are too many hydrogen bonds.

• The sequence is too long.

The diagram to the right represents part of a DNA molecule. All of the following are true about the DNA molecule above EXCEPT-

• Structure 2 represents the sugar.

• Structure 1 represents the phosphate group.

• Structure 3 is an example of a peptide bond. (peptide bonds hold together amino acids in proteins)

• Structure 4 represents a nitrogenous base.

Genes for medically important proteins can be cloned (copied) and inserted into bacteria, as shown in the diagram below.

Why can bacteria produce (make) human proteins?

• Bacteria and humans have the same number of chromosomes.

• Bacteria and humans are both eukaryotic.

• The basic components of DNA are the same in bacteria and humans.

• DNA for both bacteria and humans is contained in the nucleus.

Scientists compare a specific type of enzyme from two species. One species is a bacterium that lives in hot springs. The other species is a shrimp that lives in cold ocean water. The scientists observe the activity of the enzyme from each species over a range of temperatures from 0° C to 100° C. Which of the following statements describes what the scientists most likely observe?

• The bacterial enzyme works faster than the shrimp enzyme at all temperatures.

• The bacterial enzyme has a different optimum temperature than the shrimp enzyme

• The bacterial enzyme denatures faster than the shrimp enzyme at room temperature.

• The bacterial enzyme catalyzes more reactions than the shrimp enzyme at room temperature

Aldovanda vesiculosa and Dionaea muscipula are both species of carnivorous plants, which means they get some of their nutrients from trapping and consuming (eating) animals, like insects. This shared method of getting nutrients is evidence that these two species-

• Live in forested ecosystems.

• Evolved through artificial selection.

• Are in the domain Protista.

• Share a common ancestor.