Gene, DNA, Chromosomes
Genes, DNA and Chromosomes:
A gene is a segment of a long string of chromosome that is made up of DNA. DNA is made up of 4 chemical letters, AGCT, that are organized in a specific order, or sequence. Every gene has a unique sequence that instructs specific functions and as a whole, genes carry instructions to guide our body to grow, differentiate and develop.
Each human body contains about 25,000 different genes. Every gene has tow copies, one from father and the other from mother. The genes lay on 46 chromosomes, taking up about 2% of total DNA. The rest of 98% DNA are non-coding DNA.
The functions of the non-coding DNA are not fully understood. Non-coding DNA includes:
Regulatory elements, determining when and where genes are turned on and off, such as promoters, enhancers, etc.
Structural elements, such as telemere (repeated sequences at the ends of chromosomes), satellite DNA (bases of the centromere)
Introns
Genes:
A gene is the basic physical and functional unit of heredity. All organisms, including animals, plants, and even bacteria have genes. Genes carry instructions telling our body how to develop, differentiate and grow. Genes are like the brain of a cell telling every part of the cell what to do. Genes are like the software of a computer. Computer software is programed to guide a computer what, when and how to do jobs while genes are programed to guid our cells how to function. Genes are the genetic material that can be passed on from generation to generation.
In humans, there are about 25,000 different genes. Each gene has two copies, one from father and the other from mother. Genes also carry information that determines your traits. Traits are features or characteristics that are passed on to you from your parents, such as skin color, eye color, hair color or height, etc.
Where are genes in your body?
In humans,
Most genes are on chromosomes.
A gene is a segment of a long string of DNA.
A chromosome is a long DNA string that carries many genes and other genetic components.
Chromosomes are in the nucleus of a cell.
Nucleus is an organelle of a cell that contains chromosomes.
A small amount of DNA carrying 37 genes is in mitochondria of cells.
Mitochondria are structures within cells that convert the energy from food into a form that cells can use (such as ATP).
A small amount of DNA is in other organisms living in our body.
DNA:
DNA is the hereditary material in humans and almost all other organisms; it is made up of 4 chemical letters: A (adenine, G (guanine), C (cytosine), and thymine (T). Certain number of the 4 letters appear in certain order to form a certain gene.
In humans,
Human DNA consists of about 3 billion chemical letters, and 99% of those letters are the same in all people.
The order, or sequence, of these letters determines the information available for building and maintaining an organism, similar to the way in which letters of the alphabet appear in a certain order to form words and sentences.
A gene is a segment of DNA carrying specific instructions according to its unique sequence of these chemical letters.
Genes vary in size from a few hundred to more than 2 million DNA chemical letters.
Chromosomes:
In the nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes. Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure.
How many different chromosomes does a human body have?
We have 46 total, 23 pairs of, 24 different chromosomes and they are in most of our cells (except mature red blood cells and blood platelets, etc.).
Among the 23 pairs of chromosomes, there are 22 pairs of autosomal chromosomes. The paired chromosomes are the same; one is from father and the other is from mother. There is also a pair of sex chromosomes, either X and X for a girl or X and Y for a boy. X and Y are different chromosomes; the mother passes on X to offsprings and the father passes on either X or Y to offsprings.
A small amount of DNA is in mitochondria.
https://www.genome.gov/about-genomics/fact-sheets/Chromosomes-Fact-Sheet
Cells:
Cells are the basic building blocks of all living things. Cells contain the body's hereditary material and can make copies of themselves.
In humans,
The body is composed of trillions of cells (37.2 trillion)
Cells provide structure for the body
Cells take in nutrients from food
Cells convert nutrients into energy
Cells carry out specialized functions
Cells have many parts, such as cytoskeleton, cytoplasm, plasma membrane, endoplasmic reticulum (ER), Golgi apparatus, nucleus, lysosomes, peroxisomes, ribosomes, mitochondria, etc.
Mitochondria:
Mitochondria are structures within cells that convert the energy from food into a form that cells can use (such as ATP).
In human,
Each cell (except mature red blood cells/blood platelets) contains hundreds to thousands of mitochondria
Mitochondria are located in the fluid that surrounds the nucleus (the cytoplasm).
Mitochondrial DNA, also known as mtDNA, contains 37 genes, all of which are essential for normal mitochondrial function.
There are 16500 chemical letters in mtDNA.