Biology Questions and Answers

Answer: C

Capillary walls are only one cell thick.

That single layer of flattened endothelium is what allows oxygen, carbon dioxide, nutrients and waste to diffuse between blood and tissue. A capillary is about 8 micrometres across, so red cells pass through in single file.

Answer: B

The mismatched pair is Van Leeuwenhoek – germ theory.

He first saw bacteria, in 1676, but the germ theory of disease was established by Pasteur and Koch two centuries later. Hooke named the cell, Lister introduced antiseptic surgery and Jenner the smallpox vaccine.

Answer: B

RNA contains the sugar ribose.

DNA contains deoxyribose, which lacks one oxygen atom at the 2′ position. That missing hydroxyl is what makes DNA the more stable of the two and suits it to long-term storage of information.

Answer: B

Synapsis occurs during meiosis, in prophase I.

Homologous chromosomes pair along their length to form bivalents, and crossing over exchanges segments between them. This is the source of genetic recombination, and it does not happen in mitosis.

Answer: D

Bacterial replication begins with DNA replication.

The circular chromosome is copied from a single origin; the two copies then attach to the plasma membrane and are drawn apart as the cell grows, and only then does the membrane pinch inward and the daughter cells separate.

Answer: D

DNA replication does not occur during mitosis - it happens earlier, in the S phase of interphase.

By the time mitosis begins each chromosome already consists of two identical chromatids. Mitosis then condenses the chromosomes, breaks down the nuclear membrane, forms the spindle and separates the chromatids.

Answer: A

Bacteria divide by binary fission.

The chromosome is replicated, the copies move apart and the cell divides into two identical daughters. Under good conditions a bacterium may divide every twenty minutes, which is why a colony grows so fast.

Answer: C

Nucleoli are present during interphase.

The nucleolus is where ribosomal RNA is made and ribosomes assembled, and it needs an intact nucleus. It disappears at prophase when the nuclear membrane breaks down and reappears at telophase.

Answer: A

Arteries carry blood away from the heart.

They have thick walls of muscle and elastic tissue to withstand the pressure of each ventricular contraction and to smooth the flow between beats. The one exception to the oxygen rule is the pulmonary artery, which carries deoxygenated blood.

Answer: D

Nucleic acids are built from nucleotides.

Each nucleotide is a pentose sugar, a phosphate group and a nitrogenous base, linked into a chain by phosphodiester bonds. DNA and RNA are themselves polymers of nucleotides, not their building blocks.