Problem 4 - Biology Concepts and Applications

Question

The chromosome number is _______ . a. the sum of all chromosomes in a cell of a given type b. an identifiable feature of each species c. maintained by mitosis d. all of the above

Step-by-Step Solution

Answer

Option (d) all of the above is correct.

Step 1: Understanding the Question

The question asks for the definition of 'chromosome number' and provides four options. Our job is to determine which option properly describes 'chromosome number'.

Step 2: Option Analysis: (a) the sum of all chromosomes in a cell of a given type

Option (a) is correct because the chromosome number refers to the total count of chromosomes in a cell of a given type, such as somatic or sex cells.

Step 3: Option Analysis: (b) an identifiable feature of each species

Option (b) is correct because each species has a specific and identifiable chromosome number that distinguishes it, for example, humans have 46 chromosomes.

Step 4: Option Analysis: (c) maintained by mitosis

Option (c) is correct because mitosis is the process that ensures the chromosome number is conserved in daughter cells, as they receive an identical chromosome set as the parent cell.

Step 5: Option Analysis: (d) all of the above

Option (d) combines all previous options. Since all three statement about chromosome number are true, Option (d) must be correct.

Key Concepts

Species Identification and Chromosome Numbers

Each species on Earth has a unique set of characteristics that differentiate it from others. One such characteristic is its chromosome number. A chromosome is a DNA molecule containing part or all of the genetic material of an organism. The number of these chromosomes is specific to each species and is a key feature used in species identification. For example, humans have 46 chromosomes, gorillas have 48, and fruit flies have 8. This number helps scientists identify and classify organisms based on genetic information. It is crucial for understanding the biodiversity and evolutionary relationships between different species.

Mitosis and Chromosome Number Conservation

Mitosis is a fundamental process of cell division that ensures genetic continuity across generations of cells. During mitosis, a single cell divides to produce two identical daughter cells, each containing the same chromosome number as the original parent cell. This process consists of several stages that meticulously ensure the chromosomes are accurately copied and evenly distributed to the daughter cells.

• First, during the interphase, the cell prepares by duplicating its DNA so that each chromosome is copied.
• Then, during prophase, the chromosomes condense and become visible under a microscope.
• In metaphase, chromosomes align in the center of the cell.
• During anaphase, sister chromatids are pulled apart to opposite sides of the cell.
• Finally, in telophase and cytokinesis, the cell splits, forming two new cells with identical chromosome numbers.

This precise regulation of chromosome distribution is what maintains the integrity of genetic information through generations.

Somatic and Sex Cells: Different Roles, Same Chromosome Count

Chromosomes are found in all cells of the body, but they can be categorized based on the type of cell. Each somatic cell, which is any cell forming the body of an organism except gametes, contains the full set of chromosomes. For humans, this means each somatic cell has 46 chromosomes, arranged in 23 pairs. These cells undergo the process of mitosis to replicate and maintain their chromosome number.
Sex cells, or gametes, are different. In humans, these are the sperm cells in males and egg cells in females. Instead of undergoing typical mitosis, sex cells are produced through a process called meiosis, which results in cells having half the chromosome number of somatic cells — 23 chromosomes in humans. When two gametes unite during fertilization, they form a complete set of chromosomes, restoring the full chromosome number in the resulting zygote. This intricate coordination ensures proper development and functioning of organisms.