Chromosomes are thread-like structures comprising DNA that are present inside the nucleus of every cell in the body. Specific segments of DNA are called genes.

Every chromosome contains many genes, with each having a different function. For example, some instruct cells on how to make certain proteins. Overall, the function of chromosomes and genes is to tell cells how to replicate, informing how the body grows and develops.

In this article, we will look at the differences between genes versus chromosomes, what each one does, and how they affect health.

A note about sex and gender

Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Click here to learn more.

Was this helpful?
Collage of a double helix of DNA next to an image of chromosomes.Share on Pinterest
Design by MNT; Photography by Burazin/Getty Images & SCIEPRO/Getty Images

Nearly every cell in the body contains a nucleus. Inside each nucleus are chromosomes, which consist of DNA, the genetic material that instructs cells how to divide and grow.

Chromosomes have a cross or butterfly-like shape, with four arms — most human cells contain 23 pairs of them. One set comes from each of a person’s biological parents.

One of these 23 pairs is a set of sex chromosomes, which influences someone’s biological sex. If a person inherits two copies of the X sex chromosome, they will likely have female characteristics. If they inherit one copy of the X chromosome and one of the Y chromosome, they will likely have male characteristics.

The other 22 pairs of chromosomes in each cell are responsible for other characteristics. The scientific name for these is autosomes.

Genes are specific segments of DNA coiled around a chromosome. It is necessary to understand what DNA is in more detail to understand them.

DNA consists of four chemicals, or “bases.” They are:

  • adenine (A)
  • guanine (G)
  • cytosine (C)
  • thymine (T)

These bases pair up with other molecules to form nucleotides, the building blocks of DNA.

Genes are sequences of these nucleotides — some are large and contain millions of bases. Others are small and only contain a few hundred.

While many genes are singular, many others are present in multiple copies. Copies of the same gene can appear on different chromosomes, boosting the survivability of humans as a species.

Each gene is responsible for different functions. For example, some tell cells how to produce certain proteins, others inform characteristics such as eye or hair color, and others control growth and bodily function.

Similarly to chromosomes, people inherit genes in pairs: one copy comes from each of a person’s biological parents. Most humans inherit the same genes.

However, some genes have variations. Fewer than 1% of someone’s genes are different from the rest of the population, but these small differences can have a significant impact on health.

The table below summarizes some of the key differences between genes and chromosomes.

locationinside cell nucleion chromosomes
number23 pairs in most cells20,000–25,000
shapecross-shaped with four armschains of DNA bases that vary in length

Both genes and chromosomes can have variations that influence health. Some variations directly cause health conditions, while others may only raise or lower the risk of a condition.

Chromosomal variations involve larger-scale changes than genetic variations and may involve:

  • differences in the number of chromosomes inside cells
  • changes in the structure or function of a specific chromosome or autosome
  • the rearrangement, duplication, or deletion of segments of whole genes in a chromosome

In contrast, genetic changes are smaller in scale. Some variations in genes do not affect a person’s health, while others do. The different types of gene variation include:

  • substitution, which is when one nucleotide replaces another
  • insertion, which adds extra nucleotides
  • duplication, which repeats existing nucleotides
  • deletion, which removes one or more nucleotides
  • deletion-insertion, which removes one nucleotide and adds another
  • inversion, which reverses the sequence of nucleotides
  • frameshift, which shifts the position of many nucleotides in a gene
  • repeat expansion, which duplicates repeated sequences of nucleotides

People typically inherit gene and chromosome variants from their biological parents, but changes in the structure or function of both can also take place during a person’s lifetime.

RNA is similar to DNA in that it also carries genetic information. However, there are several differences in their function, structure, and how they operate.

DNA is responsible for the long-term storage of genetic information in the nuclei of cells. The job of RNA is to transfer that information out of the nucleus and into ribosomes, another part of the cell.

Ribosomes can then use this information to make proteins. So, where DNA acts as storage for a person’s genetic code, RNA acts as a messenger, allowing cells to use it.

Additionally, while DNA replicates itself, RNA cannot. Instead, the body makes it out of DNA as often as necessary. They also have different shapes: DNA forms a double helix, while RNA is a single helix.

Below are the definitions of other technical terms relating to genes and chromosomes:

  • Genome: This refers collectively to all of the genes a species has. For example, the human genome includes all the genes humans typically possess.
  • Genotype: This is the unique collection of genetic material belonging to an organism.
  • Phenotype: This describes observable genetic traits, such as eye color and blood type.
  • Genomics: Genomics is the study of a whole genome, or part of a genome, including how different genes interact with each other.
  • Epigenetics: This is the study of how environment and behavior affect how genes work.

Genes and chromosomes are both different types of genetic material. Chromosomes are thread-like structures that sit in the nucleus of cells and consist of chains of tightly coiled DNA. Genes are segments of DNA strands.

Most cells in the human body contain 23 pairs of chromosomes, which includes 22 pairs of autosomes and one pair of sex chromosomes. The latter influence biological sex.

There are thousands of genes on these 23 pairs of chromosomes, and variations in either the chromosome or the gene’s structure can result in health conditions.