Chromosome

Definition

A chromosome is a long, thread-like structure composed of DNA and proteins that carries genetic information. Chromosomes play a critical role in the organization, replication, and distribution of genetic material during cell division, ensuring that each new cell receives an accurate copy of the organism's genome. They exist in pairs in most organisms, with one chromosome inherited from each parent, contributing to genetic diversity.

5 Must Know Facts For Your Next Test

1. Humans typically have 46 chromosomes arranged in 23 pairs, with one set inherited from each parent.
2. Chromosomes are visible under a microscope during cell division when they condense and become distinct structures.
3. The number of chromosomes varies widely among different species; for example, fruit flies have 8, while dogs have 78.
4. During DNA replication, each chromosome is duplicated, resulting in sister chromatids that are separated during cell division.
5. Abnormalities in chromosome number or structure can lead to genetic disorders, such as Down syndrome, which is caused by an extra copy of chromosome 21.

Review Questions

• How do chromosomes ensure accurate genetic inheritance during cell division?
  • Chromosomes ensure accurate genetic inheritance by organizing DNA into manageable structures that can be duplicated and evenly distributed to daughter cells during cell division. When a cell prepares to divide, it replicates each chromosome so that two identical copies, known as sister chromatids, are formed. These chromatids are then separated into two new cells, ensuring that each daughter cell receives a complete set of chromosomes.
• Discuss the relationship between chromosomes and genes in the context of genetic variation.
  • Chromosomes serve as carriers of genes, which are specific sequences of DNA that dictate traits and characteristics. Each chromosome can contain hundreds to thousands of genes arranged along its length. The pairing of chromosomes from each parent introduces genetic variation through processes like recombination during meiosis. This shuffling of genes contributes to the diversity seen within populations and is essential for evolution.
• Evaluate how abnormalities in chromosome structure or number impact human health and development.
  • Abnormalities in chromosome structure or number can lead to significant health issues and developmental disorders. For instance, an extra chromosome (trisomy) can result in conditions like Down syndrome, where individuals have three copies of chromosome 21. Other abnormalities can include deletions or duplications of segments within chromosomes, which may disrupt gene function and lead to various syndromes or cancers. Understanding these abnormalities is crucial for developing diagnostic tools and treatment strategies in medical genetics.

Related terms

DNA: Deoxyribonucleic acid (DNA) is the molecule that contains the genetic instructions for the development and functioning of living organisms, forming the structural basis of chromosomes.

Gene: A gene is a specific segment of DNA on a chromosome that contains the instructions for making a particular protein or function, influencing traits and characteristics.

Chromatin: Chromatin is the complex of DNA and proteins found in chromosomes, existing in two forms: euchromatin (less condensed) and heterochromatin (more condensed), affecting gene expression.