Chromosomes (Role in Inheritance) — Overview & Importance

What Are Chromosomes?

Living organisms need extensive genetic information to function. In order for all of this information to fit inside each cell, it needs to be compact. This is the function of the chromosome.

The figure above shows how DNA is condensed into chromosomes. Each chromosome is made up of a single molecule of DNA, and each species has a different number of chromosomes.

To form a chromosome, DNA is first wrapped around proteins called histones. The DNA-histone complex is called a nucleosome. From here, DNA is further coiled into chromatin. Chromatin can be super-coiled to form a chromosome. However, chromosomes are only seen during cell division. Normally, DNA exists in the form of chromatin.

The diagram above shows different parts of the chromosome. Each chromosome is made of two sister chromatids. Chromatids separate during cell division (mitosis or meiosis). After separation, each chromatid is called a chromosome (see figure below for more details on this). The chromatids are joined in the middle by a centromere. Each chromosome has a short arm (p) and a long arm (q).

When a cell divides, chromatin condenses to form chromosomes. These chromosomes need to be replicated so that when the parent cell divides, each new cell gets all the genetic information it needs. This is especially important in sex cells, which go on to be fertilized to produce offspring. If there is a problem during the segregation and separation of chromosomes of sex cells, it may cause genetic mutations in the offspring.

What Is a Chromosome?

A chromosome is a single, coiled piece of DNA and protein. They contain several genes that carry genetic information. Every species has a characteristic number of chromosomes; humans have 23 pairs, including one pair of sex chromosomes.

To form a chromosome, DNA has to be wrapped tightly around proteins known as histones. The histones keep it from unwinding when it's not supposed to. The histones have to be moved out of the way if the cell wants to access the DNA.

The DNA of a chromosome has the information needed to make proteins. The genetic information is organized into hundreds of genes per chromosome.

Chromosomes form during cell division (mitosis or meiosis) so the genetic information can be properly duplicated and divided. They are formed from a material called chromatin, which is made of DNA and proteins.

Each chromosome is actually made of two identical sister chromatids that are connected at a centromere. The sister chromatids contain the same genetic information.

Summary:

• DNA and proteins make up chromatin.

• Chromatin coils up to make chromatids.

• Chromatids are joined at a centromere to form a chromosome.

$$\color{#8925AE}{\text{Vocabulary Review:}}$$

$\color{#8925AE}{\text{Chromosome}}$ : A chromosome is a long, single, coiled piece of DNA

$\color{#8925AE}{\text{DNA}}$ : The macromolecule that stores all of an organism's genetic information

$\color{#8925AE}{\text{Gene}}$ : A segment of DNA that codes for a specific trait or protein

$\color{#8925AE}{\text{Allele}}$ : Genes of the same type that contain different kinds of information

(Video) What Is a Chromosome?

by red Orbit

DNA might seem small, but it has a huge role in creating who you are. In this video, red Orbit explains what a chromosome is, what it does, and where it's found.