Which of the following best defines a genome in modern biology?

Introduction / Context:
This question examines your understanding of the term genome, a key concept in genetics and genomics. The word genome is widely used in discussions of sequencing projects, personalized medicine, and evolutionary biology. Knowing its precise meaning is essential for interpreting modern biological research.

Given Data / Assumptions:

• The term genome is being used in the context of an organism genetic material.
• The options describe cells, DNA sequences, polypeptides, and karyotypes.
• We must select the description that matches the accepted definition of a genome.
• We assume standard usage in molecular biology.

Concept / Approach:
The genome is defined as the complete set of DNA sequences in an organism, including all of its genes and noncoding regions in the nuclear and, where relevant, organelle DNA. It does not refer to individual cells, which contain copies of the genome, nor to proteins, which are gene products. A karyotype is a display of chromosomes but not a direct definition of the genome. By matching this understanding to the options, we can choose correctly.

Step-by-Step Solution:
Step 1: Recall that a genome is the entirety of an organism hereditary information encoded in DNA.Step 2: This includes all genes, regulatory sequences, and noncoding DNA segments.Step 3: Every cell with a nucleus has a copy of this genome, but the cells themselves are not the genome.Step 4: Proteins and polypeptides are products of gene expression and are not the genome.Step 5: A karyotype is a visual representation of chromosome number and structure, not the full sequence level definition.Step 6: Therefore, the correct definition is the complete set of an organism DNA sequences, including all genes.

Verification / Alternative check:
Think of famous projects such as the Human Genome Project. Their goal was to determine the entire DNA sequence of human chromosomes, not to catalog every protein or cell. This reinforces that the genome refers to all DNA information, including coding and noncoding regions.

Why Other Options Are Wrong:
Every human cell: This describes the cellular makeup of the body, not the abstract set of DNA sequences that make up the genome.
Complete set of polypeptides: The total set of proteins is sometimes called the proteome, which is distinct from the genome.
A karyotype: A karyotype displays the number and appearance of chromosomes under a microscope, but it does not capture the full DNA sequence information and therefore is not the same as the genome.

Common Pitfalls:
Students often confuse genome with similar sounding terms like proteome or karyotype. Another pitfall is thinking of the genome as a collection of cells rather than the DNA information contained within cells. Keeping the focus on DNA sequences helps maintain clarity.

Final Answer:
A genome is The complete set of an organism DNA sequences, including all genes.