Problem 2 - Biology Today and Tomorrow with Physiology

Question

A cell with two of each type of chromosome has a chromosome number that is ________ a. diploid b. haploid c. tetraploid d. abnormal

Step-by-Step Solution

Answer

a. diploid

Step 1: Understand the Definitions

First, understand the definition of the terms provided as options. A diploid cell (2n) contains two sets of chromosomes, one from each parent. A haploid cell (n) has only one set of chromosomes, which is half of the diploid number. Tetraploid (4n) cells have four sets of chromosomes. An abnormal chromosome number is any number that doesn't fit these common categories and may indicate a genetic error.

Step 2: Identify the Chromosome Number

We are told the cell has two of each type of chromosome. This is characteristic of a diploid cell, as diploid refers to having pairs of homologous chromosomes. In humans, this is typically represented as having two sets, thus making the cell diploid.

Step 3: Select the Correct Option

Based on the definitions and the characteristic mentioned in the problem (two of each type of chromosome), the correct choice that matches this description is 'diploid', which is option a.

Key Concepts

Diploid

In cell biology, understanding the term "diploid" is crucial as it describes one of the fundamental types of cell organization. Diploid cells are denoted by the symbol \(2n\), which means they contain two complete sets of chromosomes. One set comes from each parent, making such cells involved in sexual reproduction. In humans, the diploid number is \(46\) chromosomes, organized into \(23\) pairs. Since each pair consists of one chromosome from each parent, these cells carry genetic information from both maternal and paternal sources.

Diploid cells are found throughout most of an organism's body, composing what is known as "somatic cells." This includes tissue cells like skin, organs, and blood cells. When cells divide via mitosis, they maintain this diploid status, ensuring proper development and function of the organism.

• Key feature: two sets of chromosomes per cell
• Role: Contain genetic information from both parents
• Found in: All somatic cells

This duality of chromosomes supports genetic diversity and proper chromosomal distribution during reproduction, crucial for species variation and adaptation.

Haploid

The term "haploid" defines a cell with a single set of chromosomes, represented by \(n\). Such cells are essential in the process of sexual reproduction, where they act as gametes. In humans, haploid cells are the sperm and egg cells, each containing \(23\) chromosomes. When these gametes unite during fertilization, they form a diploid zygote with \(46\) chromosomes, restoring the diploid state.

The process of forming haploid cells from diploid cells is called meiosis. This specialized form of cell division reduces the chromosome number by half, creating genetic diversity by shuffling genetic material between chromosomes. Haploid cells, by having only one chromosome set, carry genetic instructions half provided by each parent.

• Key feature: single set of chromosomes per cell
• Role: Participate in sexual reproduction
• Found in: Gametes (sperm and egg cells)

Haploidy ensures that when gametes combine, the resulting zygote has a normal diploid number, preserving the chromosomal integrity across generations.

Chromosome

Chromosomes are vital structures within cells that consist of DNA and proteins, containing the genetic blueprint for an organism. The number of chromosomes varies significantly across different species, but in humans, it is normally \(46\). These chromosomes hold genes, which dictate everything from eye color to the risk of developing certain diseases.

Each chromosome pairs up with its counterpart, forming what are called "homologous pairs" in diploid cells. This pairing is integral to genetic stability and the accurate segregation of chromosomes during cell division processes, such as mitosis and meiosis. Chromosome numbers are crucial in identifying ploidy levels of a cell:

• Diploid (\(2n\)): two sets of chromosomes, one from each parent
• Haploid (\(n\)): single set of chromosomes, present in gametes
• Tetraploid (\(4n\)): four sets of chromosomes, often seen in certain plants

Anomalies in chromosome number can lead to conditions such as Down syndrome, caused by having an extra chromosome \(21\). These deviations underscore the importance of chromosomal integrity for healthy development and function.