imagine that two parents both carry the recessive gene for cystic fibrosis any homozygous recessive offspring will manifest the disease what percentag

HESI A2

Biology HESI A2 2024

1. Imagine that two parents both carry the recessive gene for cystic fibrosis. Any homozygous recessive offspring will manifest the disease. What percentage of the offspring is predicted to be carriers but not manifest the disease?

A. 0%
B. 25%
C. 50%
D. 100%

Correct answer: B

Rationale: When both parents carry the recessive gene for cystic fibrosis (homozygous recessive), there is a 25% chance for each offspring to inherit two recessive alleles and, therefore, manifest the disease. There is also a 50% chance for each offspring to inherit one recessive allele and one dominant allele, making them carriers of the disease but not manifest it. Therefore, 25% of the offspring are predicted to be carriers but not manifest the disease. Choice A (0%) is incorrect because there is a portion of offspring that will be carriers. Choice C (50%) is incorrect as this percentage corresponds to carriers who will not manifest the disease. Choice D (100%) is incorrect as not all offspring will be carriers and not manifest the disease.

2. What is DNA made of?

A. Proteins
B. Nucleotides
C. Lipids
D. Carbohydrates

Correct answer: B

Rationale: DNA is made up of nucleotides, which are the building blocks of genetic material. Choice A (Proteins) is incorrect because while proteins play a crucial role in the body, they are not the building blocks of DNA. Choice C (Lipids) and Choice D (Carbohydrates) are also incorrect as they are not the primary components of DNA.

3. What propels the cell forward?

A. Microfilaments
B. Propulsion
C. Cilia
D. Flagella

Correct answer: B

Rationale: Propulsion, not microfilaments, cilia, or flagella, is what drives the cell forward. Propulsion is the force or process that propels the cell forward and allows it to move within its environment. Microfilaments are involved in cell structure, cilia are small hair-like structures for movement, and flagella are tail-like structures used for cell propulsion in some organisms.

4. Which of the following is not found within a bacterial cell?

A. mitochondria
B. DNA
C. vesicles
D. ribosome

Correct answer: A

Rationale: The correct answer is A: mitochondria. Mitochondria are not found in bacterial cells. Bacterial cells lack membrane-bound organelles like mitochondria, which are commonly found in eukaryotic cells. Choices B, C, and D are all components that can be found within a bacterial cell. Bacterial cells contain DNA as their genetic material, vesicles for various cellular functions, and ribosomes for protein synthesis. Therefore, the presence of mitochondria is the distinguishing factor that is not found in bacterial cells, making option A the correct answer.

5. From which component do RNA and DNA derive their names?

A. From the sugar each contains
B. From the structure of their nucleotides
C. From the information they transfer
D. From their formative processes

Correct answer: A

Rationale: RNA and DNA derive their names from the sugar each contains. RNA stands for Ribonucleic Acid, with 'ribo' indicating the ribose sugar in its structure. DNA stands for Deoxyribonucleic Acid, with 'deoxyribo' referring to the deoxyribose sugar in its structure. The sugars in RNA and DNA molecules distinguish them and are the basis for their names. Choices B, C, and D are incorrect as they do not accurately explain how RNA and DNA derive their names.