Introduction to genetics

You look like your parents.

You get this from tiny parts called genes. Genes carry instructions for your body. They can decide your hair color. They can even help decide your height.

Some parts come from your mom. Other parts come from your dad. These parts work together inside you.

This is why you might have brown hair.

Sometimes, your food helps you grow. If you do not eat well, you might stay short. This is because your surroundings matter too.

Genes are made of a long string. This string is called DNA. It holds all your special information.

Sometimes, the string changes in a tiny way. These changes are called mutations. They can make new traits. This is how living things change over time.

Genetics is the study of genes. Genes are how living things get traits from their parents.

Traits can be things you see, like eye color. Some traits are not easy to see, like blood types.

Genes are made of a long molecule called DNA. DNA is made of small units. These units follow a special order. This order is the genetic code. It acts like instructions for your body. Genes tell your cells how to make proteins. Proteins are the parts that do work in your cells.

Each gene can have different versions. We call these versions alleles. One allele might make hair dark. A different allele might make hair white.

Sometimes, the DNA changes by mistake. We call these changes mutations. Mutations can make new alleles. This helps living things change over time.

DNA can also copy itself. This is called DNA replication. The DNA strands pull apart like a zipper. New units join the strands to make two new pieces.

This is how genes pass from parents to children.

Genetics is the study of genes and how they work. Genes are how living things inherit traits from their ancestors.

Some traits are easy to see, like eye color or height. Other traits are harder to see, like blood types or how a body fights disease. A child might inherit a tendency to be tall from a parent. However, the environment also matters for these traits. For example, a child might stay short if they do not get enough food.

Genes are made of a long molecule called DNA. DNA is built from simple units called nucleotides. These units follow a specific order known as the genetic code.

This code acts like a set of instructions for a living thing. The instructions tell cells how to make proteins. Proteins are the workers that carry out tasks in a cell. They can build new parts or repair damage. Each protein has a special shape that helps it do its job.

To make a protein, a cell must read the DNA. First, the cell makes a copy of the gene called RNA. This step is called transcription. Next, a structure called a ribosome reads the RNA. It turns the RNA code into a chain of amino acids. This second step is called translation. The chain then folds into a specific shape to become a working protein. This is how the instructions in your genes become real parts of your body.

Every gene can have different versions called alleles.

One allele might give instructions for black hair. A different allele might give instructions for white hair. When parents pass genes to children, they each give one copy. A child gets one allele from their father and one from their mother. Sometimes, one allele is dominant and hides the other. In this case, the hidden one is called a recessive allele. If a child gets two recessive alleles, that trait will show up.

DNA can also copy itself through a process called DNA replication. The two strands of DNA pull apart like a zipper. New nucleotides join the strands by matching their shapes. An A always pairs with a T, and a G always pairs with a C. This is called base pairing. Sometimes, mistakes happen during this copying. These random changes are called mutations. Mutations create new alleles and can lead to evolution over time.

Genetics is the scientific study of genes and their functions. It seeks to explain how living organisms inherit specific features, or traits, from their ancestors.

These traits can be physical, such as height or eye color. Other traits are internal, like blood types or resistance to certain diseases. Genetics helps us identify which traits are passed down through generations and how that process works. By studying these patterns, scientists can understand the biological instructions that build and operate life.

At the center of genetics is DNA, a long molecule that carries genetic information. DNA is constructed from simple units called nucleotides. These nucleotides are arranged in a specific order known as the genetic code.

This code provides the essential instructions for the construction and operation of an organism. Each unique version of a single gene is known as an allele. For example, one allele might instruct a body to produce dark pigment for hair, while another might fail to produce pigment, resulting in white hair. These variations in alleles are what make individuals different from one another.

To function, genes must provide the information necessary to build molecules called proteins.

Cells are the smallest independent parts of an organism. A human body contains about 100 trillion cells. Within these cells, there is a division of labor. Genes act as the instruction manual, while proteins act as the workers. Proteins carry out tasks like building new cell parts or repairing damage. Each protein is a specialist with a specific shape. This shape allows it to bind to other molecules or act as an enzyme, which is a tiny machine that alters other molecules.

Cells use a two-step process to turn DNA instructions into functional proteins. First, the cell performs transcription. During transcription, the DNA sequence is copied into a similar molecule called RNA. This process is controlled by DNA sequences called promoters, which show the cell where genes are located. Second, the cell performs translation. The RNA copy is fed through a structure called a ribosome. The ribosome reads the RNA sequence and joins amino acids together into a chain. This chain then folds into a compact, active protein shape.

Inheritance involves the mixing of alleles from two parents. Humans have two copies of each gene. However, an egg or sperm cell only receives one copy of each gene. When an egg and sperm join to form a zygote, the offspring receives a complete set.

The resulting phenotype, or physical appearance, depends on how these alleles interact. If one allele overrides another, it is called a dominant allele. The overridden allele is called a recessive allele. For instance, if a person has one brown hair allele and one red hair allele, they may have brown hair if brown is dominant. However, if they pass the recessive allele to their children, those children might show the red hair phenotype.

Some traits follow simple patterns, but many are much more complex. Many characteristics are controlled by several genes working together. Each gene contributes a small part to the final result. Height is a good example of this multifactorial inheritance. Because so many genes are involved, there are no distinct groups of "short" or "tall" people. Instead, there is a wide, continuous range of different heights. Other traits, like eye color, are also more complex than a simple two-gene model. Furthermore, the environment can interact with genes. While eye color is not changed by nutrition, a child's growth can be stunted by poor nourishment even if they have genes for being tall.

DNA must be copied every time a cell divides through a process called DNA replication.

DNA consists of two strands that pair together like a zipper. The nucleotides are in the center, acting like the teeth of the zipper. Because of their specific shapes, nucleotides follow strict rules called base pairing. An A nucleotide must always pair with a T, and a G must pair with a C. During replication, enzymes pull the strands apart, and new nucleotides match with the old strands. This creates two new pieces of DNA, each containing one old strand and one new strand.

Sometimes, the copying process is not perfectly accurate. Random changes in the DNA sequence are called mutations. Mutations can create new alleles by changing the instructions in a gene. These changes might stop a gene from working or give it a new, helpful function. For example, a mutation in melanin genes can lead to albinism, where no pigment is produced. These random mutations are a key driver of evolution.

When an inherited trait becomes more common in a population over many generations, the population is evolving.