Nokea
The Punnett square shows that one parent carries the recessive gene for a cleft chin (c) while the other parent does not. What percentage of the parents' offspring is predicted to have a cleft chin?
- A. 25%
- B. 50%
- C. 0%
- D. 75%
Correct Answer: C
Rationale: The correct answer is 0%. If one parent carries the recessive gene for a cleft chin while the other parent does not, none of the offspring will express the recessive phenotype. This is because in order for a child to have a cleft chin, they would need to inherit the recessive gene from both parents. Therefore, although the offspring could be carriers of the gene, none are predicted to have a cleft chin. Choices A, B, and D are incorrect because the presence of the recessive gene in one parent and its absence in the other would not result in any offspring showing the cleft chin trait.
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Which of the following statements is true if a molecule exhibits adhesion?
- A. Two molecules of the same substance have the ability to stay bonded to one another
- B. The molecule has the ability to bond to or attract other molecules
- C. A molecule has the ability to increase its heat when necessary
- D. The molecule has the ability to form hydrogen bonds
Correct Answer: B
Rationale: The correct statement is that if a molecule exhibits adhesion, it has the ability to bond to or attract other molecules. Adhesion refers to the ability of a molecule to bind to or attract different types of molecules. Choice A is incorrect because adhesion is about bonding to different molecules, not the same substance. Choice C is incorrect as adhesion does not relate to the ability of a molecule to increase its heat. Choice D is incorrect because forming hydrogen bonds is a specific type of interaction and not a general characteristic of molecules exhibiting adhesion.
Which of the following do prokaryotic cells lack?
- A. A cell membrane
- B. Genetic material
- C. Cytoplasm
- D. Membrane-bound organelles
Correct Answer: D
Rationale: The correct answer is D: Prokaryotic cells lack membrane-bound organelles, such as mitochondria or a nucleus, distinguishing them from eukaryotic cells. Prokaryotic cells do have genetic material, a cell membrane, and cytoplasm. Choice A is incorrect because prokaryotic cells do have a cell membrane, which is essential for maintaining cell structure and regulating what enters and exits the cell. Choice B is incorrect because prokaryotic cells contain genetic material, typically in the form of a single circular chromosome. Choice C is incorrect because prokaryotic cells have cytoplasm, where various cellular activities take place.
The bilayer of the cellular membrane consists of phospholipids with all except which of the following scattered throughout?
- A. Nucleic acids
- B. Cholesterol
- C. Proteins
- D. Glycoproteins
Correct Answer: A
Rationale: The cellular membrane is composed of a phospholipid bilayer with cholesterol, proteins, and glycoproteins distributed throughout. Nucleic acids are not found within the cellular membrane. Cholesterol helps maintain membrane fluidity, while proteins and glycoproteins play important roles in cell signaling, transport, and structural support.
Protein synthesis begins with a process known as transcription. Where does this process occur?
- A. In the cytoplasm
- B. In the nuclear envelope
- C. In the ribosome unit
- D. In the nucleus
Correct Answer: D
Rationale: The correct answer is D: In the nucleus. Transcription, the initial step of protein synthesis, takes place in the nucleus where DNA is transcribed into mRNA. This mRNA then leaves the nucleus and enters the cytoplasm where translation occurs on the ribosomes. Choices A, B, and C are incorrect because transcription specifically occurs in the nucleus, not in the cytoplasm, nuclear envelope, or ribosome unit.
What is the composition of the cellular membrane?
- A. A bilayer of phospholipid molecules
- B. A single layer of phospholipid molecules
- C. Proteins that act as transport highways
- D. Carbohydrates
Correct Answer: A
Rationale: The cellular membrane is primarily composed of a phospholipid bilayer, which consists of two layers of phospholipid molecules. These molecules have a hydrophilic (water-attracting) head and hydrophobic (water-repelling) tail, creating a barrier that separates the internal cellular environment from the external surroundings. While proteins are embedded within this bilayer and act as transport channels, receptors, and structural support, carbohydrates are found on the outer surface of the membrane for cell recognition and signaling purposes. Therefore, the correct answer is a bilayer of phospholipid molecules.