Chromosomes

Definition

Chromosomes are structures within cells that contain DNA, the genetic material responsible for inherited traits. Each chromosome is made up of a single, long molecule of DNA that is tightly coiled and packaged with proteins to form a compact structure. The number and organization of chromosomes are crucial for proper cell division and genetic stability during the cell cycle.

5 Must Know Facts For Your Next Test

1. Humans have 46 chromosomes, arranged in 23 pairs, with one set inherited from each parent.
2. Chromosomes are only visible under a microscope during cell division when they condense and become distinct; otherwise, they exist as chromatin.
3. Each chromosome consists of two sister chromatids joined at a region called the centromere, which splits during mitosis to ensure each daughter cell receives the correct genetic information.
4. 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.
5. The process of chromosomal replication occurs during the S phase of interphase in the cell cycle, ensuring that each new cell has the same genetic material.

Review Questions

• How do chromosomes ensure genetic stability during the cell cycle?
  • Chromosomes play a vital role in maintaining genetic stability by ensuring that DNA is accurately replicated and distributed to daughter cells during cell division. During the S phase of interphase, each chromosome is duplicated to form sister chromatids. Then, during mitosis, these chromatids are separated and allocated to two new cells. This precise distribution prevents genetic errors and maintains the correct number of chromosomes in each new cell.
• Discuss the implications of chromosomal abnormalities on human health.
  • Chromosomal abnormalities can have significant effects on human health, often resulting in genetic disorders. For instance, Down syndrome arises from an extra copy of chromosome 21, leading to developmental delays and other health issues. Other conditions like Turner syndrome and Klinefelter syndrome are caused by missing or extra sex chromosomes. These abnormalities can disrupt normal biological functions and lead to a variety of physical and cognitive challenges.
• Evaluate the significance of chromatin structure in relation to gene expression during the cell cycle.
  • The structure of chromatin is crucial for regulating gene expression throughout the cell cycle. During interphase, chromatin exists in a less condensed form, allowing transcription factors access to DNA for gene expression. However, as cells prepare for division, chromatin condenses into distinct chromosomes, which helps protect DNA during mitosis. The dynamic changes in chromatin structure not only facilitate accurate DNA replication and segregation but also influence which genes are expressed at various stages of the cell cycle.

Related terms

DNA: Deoxyribonucleic acid, the molecule that carries genetic instructions for the development, functioning, growth, and reproduction of all known organisms.

Chromatin: The material that makes up chromosomes, consisting of DNA and proteins, which condenses to form distinct chromosomes during cell division.

Mitosis: The process of cell division that results in two genetically identical daughter cells, during which chromosomes are replicated and evenly distributed.