DNA, genes, chromosomes or genome. There are numerous terms that describe our human blueprint. But what do the individual terms mean and how do the individual building blocks interact?
Genetics is the study of heredity, i. H. from the traits we inherit from our parents, which they inherited from their parents, and so on. These traits are controlled by encoded information found in every cell in the body.
This code is contained in DNA, genes and chromosomes. Together, these units make up the complete set of genetic instructions for each individual—the so-called genome—including our sex, our appearance, and the diseases we may be susceptible to. No two people have the same genome.
what is a gene
A gene is the basic physical and functional unit of heredity. Genes are made up of DNA. Some genes serve as instructions for making molecules called proteins. However, many genes do not code for proteins. In humans, genes vary in size from a few hundred to more than 2 million DNA bases. An international research project, the so-called Humangenomprojekt, which determined the sequence of the human genome and identified the genes it contains, estimates that humans have between 20,000 and 25,000 genes.
Everyone has two copies of each gene, one inherited from each parent. Most genes are the same in all people, but a small number of genes (less than 1 percent of the total) differ slightly between people. Alleles are forms of the same gene with small differences in the sequence of DNA bases. These small differences contribute to each person's unique physical characteristics.
Scientists keep track of genes by giving them unique names. Since the gene names can be very long, symbols are also assigned to the genes. These are short combinations of letters (and sometimes numbers) that represent an abbreviated version of the gene name.
For example, a gene on chromosome 7 associated with cystic fibrosis is called cystic fibrosis transmembrane conductance regulator; its symbol is CFTR.
What is DNA?
DNA, or deoxyribonucleic acid, is the genetic material of humans and almost all other organisms. Almost every cell in the human body has the same DNA. Most DNA is found in the cell's nucleus (where it's called nuclear DNA), but a small amount of DNA is also found in the mitochondria (where it's called mitochondrial DNA, or mtDNA). Mitochondria are structures in cells that convert energy from food into a form that cells can use.
Information in DNA is stored as a code made up of four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T). Human DNA is made up of approximately 3 billion bases, and more than 99 percent of those bases are common to all people. The order or sequence of these bases determines the information available for building and maintaining an organism, much like the letters of the alphabet appear in a specific order to form words and sentences.
DNA bases pair with each other, A with T and C with G, to form units called base pairs. Each base is also connected to a sugar molecule and a phosphate molecule. Together, a base, a sugar, and a phosphate form a nucleotide. Nucleotides are arranged in two long strands that form a spiral called a double helix. The structure of the double helix resembles a ladder, with the base pairs forming the rungs of the ladder and the sugar and phosphate molecules forming the vertical sides of the ladder.
An important property of DNA is its ability to replicate, i. H. the ability to make copies of themselves. Each strand of DNA in the double helix can serve as a template for amplification of the base sequence. This is crucial when cells are dividing, as each new cell must have an exact copy of the DNA present in the old cell.
What are chromosomes?
A chromosome is a structure that cells use to organize their DNA when dividing. During normal cell operation, DNA is in the form of chromatin, which is not visible under a microscope. However, during cell replication, DNA is bound into a series of chromosomes. The exact number varies depending on the species. The chromosome consists of a bundle of DNA and some structural proteins called histones. Most are x-shaped and symmetrical. At its center is a structure called the centromere that holds the two halves together. Humans have 46 chromosomes.
How are genes, DNA and chromosomes related?
To understand how these parts fit together, it helps to visualize the function of each part.
The gene is the idea or blueprint. DNA is the language or the way genes are written down. Chromosomes are structures that cells use to organize their DNA for cell division.
Chromosomes typically contain thousands of genes written in DNA. Since there are exceptions to almost every rule in biology, there are a few situations where genes are written in something other than DNA, such as the RNA of viruses and the proteins of prions, but none of these are universally considered alive.