Molecular evolution

Tiny parts inside us change over time.

These changes are called mutations. They can happen by mistake.

Sometimes, a change makes a living thing look different. These changes can help a living thing survive. Scientists look at these tiny changes to see how life is related. They can even tell how long ago two things shared a parent. This helps us learn about the history of all life.

All living things have a set of instructions. These instructions are in DNA or RNA. Over a long time, these instructions change. This is called molecular evolution.

Changes often start with a mutation. A mutation is a permanent change in the genetic material. These can happen by mistake when cells divide. They can also come from things like radiation.

Some mutations change how a protein works. Other mutations might not change anything at all.

Scientists use these changes to study the tree of life. They look at how similar DNA sequences are between species. This helps them make a phylogenetic tree. A phylogenetic tree is a map of how life is related.

Some changes help a living thing survive. This is called selection. Other changes happen by chance. This is called genetic drift. Scientists can even use these changes as a molecular clock. This helps them guess how long ago two species shared an ancestor. Different genes change at different speeds. For example, hemoglobin changes at a different rate than cytochrome c.

Molecular evolution is the study of how the instructions for life change over time. These instructions are found in molecules called DNA and RNA. As these molecules change, they affect the proteins and other parts of a cell.

This study helps scientists understand the history of all living things. It is the basis for building a tree of life. This tree shows how different species are related to one another.

Changes in these instructions often start with a mutation. A mutation is a permanent change in the genetic material. These changes can happen because of errors when a cell divides. They can also come from radiation or certain chemicals.

Some mutations are very small, called point mutations, affecting just one tiny spot. Other mutations can change large chunks of DNA by adding or moving pieces. These changes can happen at different speeds depending on the organism. For example, some viruses change much faster than most other living things.

Scientists have been studying these changes for a long time. In the early 1900s, they began looking at the chemistry of life. By the 1950s, they used special methods to look at proteins. Later, they learned how to sequence proteins to see their exact order. This allowed them to use a molecular clock to guess time. A molecular clock uses the rate of change to estimate when two species shared an ancestor. In 1982, the Society for Molecular Biology and Evolution was founded.

There are many ways these genetic changes move through a group. One way is called selection. This happens when a change helps a living thing survive or have babies. Another way is called genetic drift. This is when changes happen just by random chance in small groups.

Some changes are neutral, meaning they do not help or hurt much. Scientists also study gene conversion, which is a way cells repair damage. These different processes shape how the genome, or the set of instructions, looks.

It is interesting to see how these small changes lead to big differences. For example, different genes change at different rates. Hemoglobin changes at a different speed than a protein called cytochrome c. Even within one family of proteins, many different versions can evolve.

Sometimes, only a few mutations are needed to change what a protein does. This shows how much variety can exist in the natural world. It helps us see how complex life grew from simple beginnings.

Molecular evolution is the study of how inherited DNA and RNA change over long periods of time. These changes affect the proteins and other vital components within cells and organisms. By studying these molecular shifts, scientists can build a "tree of life" to show how different species are related.

This field overlaps with population genetics, particularly when looking at changes over shorter timescales. It explores how new genes originate and how complex traits develop through genetic changes.

The process of molecular evolution often begins with a mutation. A mutation is a permanent, transmissible change in the genetic material of a cell or virus. These can occur due to errors during DNA replication when a cell divides. Environmental stressors, such as radiation, chemicals, or viruses, can also cause these changes.

Mutations can be small, like a point mutation that affects only one base-pair. They can also be large, involving duplications, insertions, deletions, inversions, or translocations of DNA segments.

Different types of mutations happen at different rates. Most organisms have very low point mutation rates, roughly 10\u207b\(9\) to 10\u207b\(8\) per site per generation. However, some viruses have much higher rates, around 10\u207b\(6\) per site per generation. In humans, one common type of mutation involves changing the length of short tandem repeats. These changes can influence how evolution moves forward by creating a bias in the types of variation that appear.

Once a mutation exists, several forces determine if it stays in a population. Natural selection occurs when a specific version of a gene provides higher fitness. Fitness refers to an individual's ability to survive and reproduce on average. Selection can also happen at the gene level, sometimes causing conflict within the organism. For example, "selfish" genetic elements like transposable elements might benefit themselves even if they cost the host organism something.

Another force is genetic drift, which involves random changes in gene frequencies. This happens because of stochastic effects, or random sampling, in finite populations. In small populations, genetic drift is very strong. It can cause even slightly harmful mutations to become fixed, meaning they are shared by the whole group. For neutral mutations, which do not help or hurt, the rate of change is relatively constant. This constant rate allows scientists to use a "molecular clock" to estimate when species shared a common ancestor.

Scientists use molecular phylogenetics to classify organisms based on their evolutionary history. This involves aligning DNA or protein sequences to find homologous sites, which are parts that share a common origin.

Researchers use a substitution model to predict which patterns of change are common or rare.

By using computational tools, they can generate phylogenetic trees that represent these evolutionary relationships. Different genes evolve at different speeds; for instance, hemoglobin and cytochrome c change at different rates.

Evolution can also lead to massive changes in protein function. Within a single protein family, many different structural and functional mechanisms can evolve. One example is the ribonucleotide reductase (RNR) family, which has many structural variants. In some cases, only a few mutations are required to radically change a protein's job. A study showed that myoglobin could be turned into an efficient enzyme using only three mutations. This demonstrates the incredible flexibility of molecular systems over time.