Problem 2 - Campbell Biology Concepts & Connections

Question

If an intestinal cell in a grasshopper contains 24 chromosomes, then a grasshopper sperm cell contains _____ chromosomes. a. 6 b. 12 c. 24 d. 48

Step-by-Step Solution

Answer

b. 12

Step 1: Understanding Chromosome Count in Body Cells

An intestinal cell is a type of somatic (body) cell. In grasshoppers, if an intestinal cell contains 24 chromosomes, it is diploid and has two sets of chromosomes.

Step 2: Determine Chromosome Count in Sperm Cells

Sperm cells are gametes, which are produced through meiosis and contain half the number of chromosomes as somatic cells. Thus, the number of chromosomes in a grasshopper sperm cell is half of 24.

Step 3: Calculate and Select the Correct Option

Half of 24 chromosomes is 12 chromosomes. Therefore, the grasshopper sperm cell contains 12 chromosomes. Among the given options, the correct answer is b. 12.

Key Concepts

Chromosome Count

Chromosomes are structures within cells that contain DNA, the genetic material responsible for heredity and function. Each species has a specific number of chromosomes in its cells. Grasshoppers, for instance, have 24 chromosomes in their somatic (body) cells. Somatic cells include various types such as intestinal cells, skin cells, and muscle cells. These cells are typically 'diploid,' meaning they have two sets of chromosomes: one set from the mother and one set from the father. This count is consistent across all somatic cells in grasshoppers.

Gametes

Gametes are the reproductive cells involved in sexual reproduction. In grasshoppers, these are the sperm cells in males and egg cells in females. Unlike somatic cells, gametes are 'haploid,' containing only one set of chromosomes. Hence, they have half the number of chromosomes compared to somatic cells. This reduction in chromosome number is crucial as it ensures that when a sperm cell and an egg cell unite during fertilization, the resulting zygote has the correct diploid number of chromosomes.

Diploid vs Haploid

Understanding the difference between diploid and haploid cells is essential in grasping the concepts of meiosis and fertilization. Diploid cells (denoted as 2n) contain two sets of chromosomes, whereas haploid cells (denoted as n) contain only one set. In grasshoppers, the diploid number is 24 (2n = 24), which means that the haploid number is 12 (n = 12). During meiosis, a type of cell division, diploid cells divide to produce haploid gametes. This division helps maintain a stable chromosome number across generations, ensuring that offspring have the same diploid number as their parents.