Question

A diploid cell has_____________ the number of chromosomes as a haploid cell. a. one-fourth b. one-half c. twice d. four times

Short answer

c. twice

Step-by-step solution

Understanding Diploid and Haploid Cells

Diploid cells (denoted as 2n) contain two complete sets of chromosomes, while haploid cells (denoted as n) contain only one set of chromosomes. In humans, an example of diploid cells would be somatic cells (such as skin cells), and an example of haploid cells would be gametes (sperm and egg cells).

Comparing Chromosome Numbers

Since diploid cells have two sets of chromosomes and haploid cells have only one set, we can determine the relationship between their chromosome numbers by comparing the diploid chromosome number (2n) to the haploid chromosome number (n).

Selecting the Correct Answer

Comparing 2n to n, we can see that a diploid cell has twice the number of chromosomes as a haploid cell (2n = 2 * n). Therefore, the correct answer is: c. twice

Key concepts

Chromosome Number Comparison

The comparison of chromosome numbers in diploid and haploid cells is fundamental to understanding their role in biology. To simplify, a diploid cell contains a double set of chromosomes, one set inherited from each parent. Conversely, a haploid cell contains a single set of chromosomes, representing half the number of a diploid cell.

For instance, in humans, the diploid number (2n) is 46, meaning there are 23 pairs of chromosomes. If we look at haploid cells, such as human sperm or egg cells, the number is 23 (n). It is the fusion of these haploid cells during fertilization that results in a return to the diploid state. It's like thinking of the diploid as a complete two-volume encyclopedia of genetic information, while the haploid is just one volume. So, when a problem asks for the relationship between their chromosome numbers, the answer is that the diploid has twice the number - symmetrical and perfectly matched to make a new organism.

Somatic Cells

Somatic cells make up the majority of the cells in an organism and are considered diploid. These are the cells that form tissues, organs, and other bodily structures, excluding the reproductive cells. In somatic cells, chromosomes come in pairs, which is why they have the diploid number of chromosomes.

Every somatic cell in an organism contains the same DNA, with each pair of chromosomes carrying the genes that control everything from hair color to the type of enzymes produced by the body. This genetic consistency ensures that each cell can function in harmony with the rest of the body. It's a bit like every cell having the same blueprint to operate from, which is essential for the complex workings of any multicellular organism.

Gametes

In contrast to somatic cells, gametes are haploid reproductive cells, and they include sperm in males and eggs in females. These cells carry only a single set of chromosomes because their ultimate purpose is to combine with another haploid cell during fertilization to create a diploid zygote.

As a result of this combination, the zygote then has the correct diploid number of chromosomes, reflecting that it has genetic material from both parents. Without gametes being haploid, the chromosome number would double with each generation, leading to unsustainable genetic inflation. Gametes ensure a consistent chromosome number across generations, playing a critical role in heredity and variability of species.