Genome

A genome is a set of rules.

It tells a living thing how to grow. It is inside your cells.

This set of rules is made of tiny parts. These parts carry all the information. It helps a living thing be what it is.

Most of these rules are in a center part of the cell. But some rules live in other small parts too. Plants have extra rules in their green parts.

Scientists can read these rules. They use tools to see the tiny parts. This helps them learn about life.

It is a very big job. But it helps us understand everything.

A genome is the complete set of instructions for a living thing. These instructions are made of DNA. DNA is a molecule that carries genetic information.

Most of this information stays in the cell nucleus. We call this the nuclear genome. But some cells have extra DNA in other parts. Mitochondria are small parts of a cell. They have their own tiny genome. Plants and algae also have DNA in their chloroplasts.

Scientists study these instructions using a field called genomics. They use tools to find the order of the DNA. This order is called a sequence. The first genome ever sequenced was a virus in 1977. In 2001, scientists finished a draft of the human genome.

Not all DNA makes proteins. Proteins are the tools a cell uses to work. Much of the human genome is noncoding. This means it does not make proteins. It includes things like repetitive DNA. Some parts can even move to new spots. These are called transposable elements. They help life change and grow over time.

A genome is the complete set of genetic information for a living thing. This information is made of molecules called DNA or RNA. Most of this material stays inside the cell nucleus. This part is called the nuclear genome.

However, many living things have extra DNA in other places. Mitochondria have their own small mitochondrial genome. Plants and algae also have a genome inside their chloroplasts. This is often called a plastome.

To understand a genome, scientists look at the sequence. A sequence is the specific order of nucleotides. These are the building blocks called A, C, G, and T. Most of these letters are the same between different people of one species. Scientists must sequence many individuals to see genetic diversity. Some parts of the genome are coding sequences. These carry the instructions to make proteins.

Other parts are noncoding sequences. In humans, noncoding sequences make up 98% of the genome.

Learning about genomes is a field called genomics. The term genome was created in 1920 by Hans Winkler. He was a professor of botany in Germany. The name likely blends the words gene and chromosome. Scientists have worked hard to read these sequences for many years. The first genome sequenced was the φX174 virus in 1977. In 1995, researchers finished the first bacterial genome. This was the bacterium Haemophilus influenzae.

There are many important dates in the history of genomics. The Human Genome Project began in October 1990. Scientists reported the first draft of the human genome in February 2001. In 1996, the first eukaryotic genome was sequenced. This was the budding yeast Saccharomyces cerevisiae. In 2013, scientists did something amazing with ancient DNA. They sequenced the entire genome of a Neanderthal. They found this DNA in a 130,000-year-old toe bone from a Siberian cave.

Genomes can also be very strange and active. Some DNA parts are called transposable elements. These are sequences that can change their location. They can move by copying themselves or by cutting and pasting. In humans, these elements make up over 45% of our DNA. There are also tandem repeats. These are short sequences that repeat head-to-tail. Some repeats, like telomeres, protect the ends of chromosomes. Other changes in repeats can lead to human disorders.

A genome is the complete set of genetic information for an organism or a cell. This information is stored in molecules called DNA or RNA. The study of these genomes is known as genomics. Scientists use genomics to understand how life functions and evolves.

The term was first used in 1920 by Hans Winkler. He was a professor of botany at the University of Hamburg in Germany. The word is likely a blend of "gene" and "chromosome." Understanding the genome is vital because it contains the instructions for building and operating life.

In eukaryotic cells, the genome is organized into several distinct parts. The most important part is the nuclear genome. This consists of linear DNA chromosomes located inside the cell nucleus. Most eukaryotes are diploid, meaning they have two copies of each chromosome. For humans, this includes 22 pairs of autosomes and two sex chromosomes. The standard human reference genome includes one copy of each of the 22 autosomes, plus one X and one Y chromosome.

Beyond the nucleus, other organelles hold their own genetic material. Mitochondria contain a small mitochondrial genome. In plants and algae, chloroplasts also contain a genome, often called a plastome. These organelle genomes are typically circular.

Genomes vary greatly in their structure and complexity. Viruses can have genomes made of either DNA or RNA. RNA virus genomes can be single-stranded or double-stranded. They may also be monopartit, meaning one molecule, or multipartit, meaning several segments. Prokaryotes, such as bacteria and archaea, usually have a single circular chromosome. Some bacteria also carry smaller, extra DNA molecules called plasmids. These plasmids carry important genetic information separate from the main chromosome. In some symbiotic bacteria, the genome is reduced, with only about 40% of the DNA encoding proteins.

Scientists study the genome by determining its sequence. A sequence is the specific order of nucleotides, which are the building blocks A, C, G, and T. Sequencing allows researchers to see the differences between individuals. This helps them understand genetic diversity within a species. The history of sequencing is filled with major milestones. In 1976, Walter Fiers established the first complete viral RNA-genome sequence. In 1977, Fred Sanger completed the first DNA-genome sequence for the virus φX174.

This was followed by the first bacterial genome in 1995 and the first eukaryotic genome in 1996.

The Human Genome Project represents one of the most significant efforts in science. It began in October 1990. By February 2001, scientists reported the first draft sequences of the human genome. Since then, technology has made sequencing much cheaper and faster. In 2013, researchers achieved a major feat by sequencing a Neanderthal genome. They extracted this DNA from a 130,000-year-old toe bone found in a Siberian cave. This work helps us connect the history of human evolution to our own genetic code.

A genome is not just a list of instructions for proteins. It contains both coding and noncoding sequences. Coding sequences are the parts that provide instructions to make proteins. However, noncoding sequences make up a massive portion of the genome. In humans, noncoding sequences account for 98% of the total DNA. This includes regulatory regions, introns, and repetitive DNA.

Interestingly, a larger genome does not always mean an organism has more genes. The size can vary by as much as 64,000-fold due to repetitive elements.

Repetitive DNA includes two main types: tandem repeats and transposable elements. Tandem repeats are short sequences that repeat head-to-tail. For example, telomeres use the repeat TTAGGG to protect chromosome ends. However, expansions in these repeats can cause disease, such as Huntington's disease. Transposable elements, or TEs, are sequences that can change their location. They can move by copying themselves or by cutting and pasting. In humans, these elements make up more than 45% of our DNA. These elements include LINEs, SINEs, and endogenous retroviruses. Their movement helps drive the evolution of eukaryotic genomes.