# data[].attributes.body
A chromosome is a DNA molecule with part or all of the genetic material of an organism. Most Eukaryota chromosomes include packaging proteins which, aided by chaperone proteins, bind to and condense

# data[].attributes.body
a thread-like structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.

# data[].attributes.body
a thread-like structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.

# data[].attributes.body
a thread-like structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.

# data[].attributes.body
each of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.

# data[].attributes.body
andrew

# data[].attributes.body
each of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.

# data[].attributes.headline
In biology, a gene is a sequence of DNA or RNA which codes for a molecule that has a function. During gene expression, the DNA is first copied into RNA.

# data[].attributes.subject
In biology, a gene is a sequence of DNA or RNA which codes for a molecule that has a function. During gene expression, the DNA is first copied into RNA.

# data[].attributes.body
Harlee Kohn

# data[].attributes.body
the fundamental and distinctive characteristics or qualities of someone or something, especially when regarded as unchangeable.

# data[].attributes.attachment_link.readable_text
Gene therapy uses sections of DNA (usually genes) to treat or prevent disease.

The DNA is carefully selected to correct the effect of a mutated gene that is causing disease.

The technique was first developed in 1972 but has, so far, had limited success in treating human diseases.

Gene therapy may be a promising treatment option for some genetic diseases, including muscular dystrophy and cystic fibrosis.

There are two different types of gene therapy depending on which types of cells are treated:

Somatic gene therapy: transfer of a section of DNA to any cell of the body that doesn't produce sperm or eggs. Effects of gene therapy will not be passed onto the patient's children.

Germline gene therapy: transfer of a section of DNA to cells that produce eggs or sperm. Effects of gene therapy will be passed onto the patient's children and subsequent generations.

Gene therapy techniques

There are several techniques for carrying out gene therapy. These include:
Gene augmentation therapy

This is used to treat diseases caused by a mutation that stops a gene from producing a functioning product, such as a protein.

This therapy adds DNA containing a functional version of the lost gene back into the cell.

The new gene produces a functioning product at sufficient levels to replace the protein that was originally missing.

This is only successful if the effects of the disease are reversible or have not resulted in lasting damage to the body.

For example, this can be used to treat loss of function disorders such as cystic fibrosis by introducing a functional copy of the gene to correct the disease (see illustration below).

Gene inhibition therapy

Suitable for the treatment of infectious diseases, cancer and inherited disease caused by inappropriate gene activity.

The aim is to introduce a gene whose product either:

inhibits the expression of another gene

interferes with the activity of the product of another gene.

The basis of this therapy is to eliminate the activity of a gene that encourages the growth of disease-related cells.

For example, cancer is sometimes the result of the over-activation of an oncogene (gene which stimulates cell growth). So, by eliminating the activity of that oncogene through gene inhibition therapy, it is possible to prevent further cell growth and stop the cancer in its tracks.

Killing of specific cells

Suitable for diseases such as cancer that can be treated by destroying certain groups of cells.

The aim is to insert DNA into a diseased cell that causes that cell to die.

This can be achieved in one of two ways:

the inserted DNA contains a "suicide" gene that produces a highly toxic product which kills the diseased cell

the inserted DNA causes expression of a protein that marks the cells so that the diseased cells are attacked by the body's natural immune system.

It is essential with this method that the inserted DNA is targeted appropriately to avoid the death of cells that are functioning normally.

How is DNA transfer done?

A section of DNA/gene containing instructions for making a useful protein is packaged within a vector, usually a virus, bacterium or plasmid.

The vector acts as a vehicle to carry the new DNA into the cells of a patient with a genetic disease.

Once inside the cells of the patient, the DNA/gene is expressed by the cell's normal machinery leading to production of the therapeutic protein and treatment of the patient's disease.

Challenges of gene therapy

Delivering the gene to the right place and switching it on:

it is crucial that the new gene reaches the right cell

delivering a gene into the wrong cell would be inefficient and could also cause health problems for the patient

even once the right cell has been targeted the gene has to be turned on

cells sometimes obstruct this process by shutting down genes that are showing unusual activity.

Avoiding the immune response:

The role of the immune system is to fight off intruders.

Sometimes new genes introduced by gene therapy are considered potentially-harmful intruders.

This can spark an immune response in the patient, that could be harmful to them.

Scientists therefore have the challenge of finding a way to deliver genes without the immune system 'noticing'.

This is usually by using vectors that are less likely to trigger an immune response.

Making sure the new gene doesn't disrupt the function of other genes:

Ideally, a new gene introduced by gene therapy will integrate itself into the genome of the patient and continue working for the rest of their lives.

There is a risk that the new gene will insert itself into the path of another gene, disrupting its activity.

This could have damaging effects, for example, if it interferes with an important gene involved in regulating cell division, it could result in cancer.

The cost of gene therapy:

Many genetic disorders that can be targeted with gene therapy are extremely rare.

Gene therapy therefore often requires an individual, case-by-case approach. This may be effective, but may also be very expensive.

# data[].attributes.attachment_link.description
Gene therapy uses sections of DNA (usually genes) to treat or prevent disease. The DNA is carefully selected to correct the effect of a mutated gene that is causing disease. The technique was first developed in 1972 but has, so far, had limited success in treating human diseases.

# data[].attributes.body
the fundamental and distinctive characteristics or qualities of someone or something, especially when regarded as unchangeable.

# data[].attributes.body
a sequence of DNA

# data[].attributes.body
a distinguishing quality or characteristic, typically one belonging to a person.

# data[].attributes.body
a distinguishing quality or characteristic, typically one belonging to a person.

# data[].attributes.attachment_link.readable_text
Gene therapy uses sections of DNA (usually genes) to treat or prevent disease.

The DNA is carefully selected to correct the effect of a mutated gene that is causing disease.

The technique was first developed in 1972 but has, so far, had limited success in treating human diseases.

Gene therapy may be a promising treatment option for some genetic diseases, including muscular dystrophy and cystic fibrosis.

There are two different types of gene therapy depending on which types of cells are treated:

Somatic gene therapy: transfer of a section of DNA to any cell of the body that doesn't produce sperm or eggs. Effects of gene therapy will not be passed onto the patient's children.

Germline gene therapy: transfer of a section of DNA to cells that produce eggs or sperm. Effects of gene therapy will be passed onto the patient's children and subsequent generations.

Gene therapy techniques

There are several techniques for carrying out gene therapy. These include:
Gene augmentation therapy

This is used to treat diseases caused by a mutation that stops a gene from producing a functioning product, such as a protein.

This therapy adds DNA containing a functional version of the lost gene back into the cell.

The new gene produces a functioning product at sufficient levels to replace the protein that was originally missing.

This is only successful if the effects of the disease are reversible or have not resulted in lasting damage to the body.

For example, this can be used to treat loss of function disorders such as cystic fibrosis by introducing a functional copy of the gene to correct the disease (see illustration below).

Gene inhibition therapy

Suitable for the treatment of infectious diseases, cancer and inherited disease caused by inappropriate gene activity.

The aim is to introduce a gene whose product either:

inhibits the expression of another gene

interferes with the activity of the product of another gene.

The basis of this therapy is to eliminate the activity of a gene that encourages the growth of disease-related cells.

For example, cancer is sometimes the result of the over-activation of an oncogene (gene which stimulates cell growth). So, by eliminating the activity of that oncogene through gene inhibition therapy, it is possible to prevent further cell growth and stop the cancer in its tracks.

Killing of specific cells

Suitable for diseases such as cancer that can be treated by destroying certain groups of cells.

The aim is to insert DNA into a diseased cell that causes that cell to die.

This can be achieved in one of two ways:

the inserted DNA contains a "suicide" gene that produces a highly toxic product which kills the diseased cell

the inserted DNA causes expression of a protein that marks the cells so that the diseased cells are attacked by the body's natural immune system.

It is essential with this method that the inserted DNA is targeted appropriately to avoid the death of cells that are functioning normally.

How is DNA transfer done?

A section of DNA/gene containing instructions for making a useful protein is packaged within a vector, usually a virus, bacterium or plasmid.

The vector acts as a vehicle to carry the new DNA into the cells of a patient with a genetic disease.

Once inside the cells of the patient, the DNA/gene is expressed by the cell's normal machinery leading to production of the therapeutic protein and treatment of the patient's disease.

Challenges of gene therapy

Delivering the gene to the right place and switching it on:

it is crucial that the new gene reaches the right cell

delivering a gene into the wrong cell would be inefficient and could also cause health problems for the patient

even once the right cell has been targeted the gene has to be turned on

cells sometimes obstruct this process by shutting down genes that are showing unusual activity.

Avoiding the immune response:

The role of the immune system is to fight off intruders.

Sometimes new genes introduced by gene therapy are considered potentially-harmful intruders.

This can spark an immune response in the patient, that could be harmful to them.

Scientists therefore have the challenge of finding a way to deliver genes without the immune system 'noticing'.

This is usually by using vectors that are less likely to trigger an immune response.

Making sure the new gene doesn't disrupt the function of other genes:

Ideally, a new gene introduced by gene therapy will integrate itself into the genome of the patient and continue working for the rest of their lives.

There is a risk that the new gene will insert itself into the path of another gene, disrupting its activity.

This could have damaging effects, for example, if it interferes with an important gene involved in regulating cell division, it could result in cancer.

The cost of gene therapy:

Many genetic disorders that can be targeted with gene therapy are extremely rare.

Gene therapy therefore often requires an individual, case-by-case approach. This may be effective, but may also be very expensive.

# data[].attributes.attachment_link.description
Gene therapy uses sections of DNA (usually genes) to treat or prevent disease. The DNA is carefully selected to correct the effect of a mutated gene that is causing disease. The technique was first developed in 1972 but has, so far, had limited success in treating human diseases.

# data[].attributes.body
a thread-like structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.

# data[].attributes.body
like if your father is tall and your mother is tall you will become tall as well

# data[].attributes.body
each two or more alternative forms of a gene.

# data[].attributes.body
like if your father is tall and your mother is tall you will become tall as well

# data[].attributes.body
each of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.

# data[].attributes.headline
each of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome

# data[].attributes.subject
each of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome

# data[].attributes.body
Harlee Kohn

# data[].attributes.body
a gene is something thats past from parent to their children

# data[].attributes.body
In biology, a mutation is the permanent alteration of the nucleotide sequence of the genome of an organism, virus, or extra chromosomal DNA or other genetic elements

# data[].attributes.body
n informal use) a unit of heredity which is transferred from a parent to offspring and is held to determine some characteristic of the offspring.

# data[].attributes.body
an organism or cell, or group of organisms or cells, produced asexually from one ancestor or stock, to which they are genetically identical.

# data[].attributes.headline
Deoxyribonucleic acid is a thread-like chain of nucleotides carrying the genetic instructions used in the growth, development, functioning and reproduction of all known living organisms and many viruses.

# data[].attributes.subject
Deoxyribonucleic acid is a thread-like chain of nucleotides carrying the genetic instructions used in the growth, development, functioning and reproduction of all known living organisms and many viruses.

# data[].attributes.body
Harlee Kohn

# data[].attributes.body
one belonging to a person.

# data[].attributes.body
the changing of the structure of a gene, resulting in a variant form which may be transmitted to subsequent generations, caused by the alteration of single base units in DNA, or the deletion, insertion, or rearrangement of larger sections of genes or chromosomes.

# data[].attributes.body
one belong to a person

# data[].attributes.body
the process by which different kinds of living organism are believed to have developed from earlier forms during the history of the earth.

# data[].attributes.body
an organism or cell, or group of organisms or cells, produced asexually from one ancestor or stock, to which they are genetically identical.

# data[].attributes.body
an organism or cell, or group of organisms or cells, produced asexually from one ancestor or stock, to which they are genetically identical.

# data[].attributes.headline
a distinguishing quality or characteristic, typically one belonging to a person.

# data[].attributes.subject
a distinguishing quality or characteristic, typically one belonging to a person.

# data[].attributes.body
Harlee Kohn

# data[].attributes.body
each of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.

# data[].attributes.body
like if your parents are tall you will be tall

# data[].attributes.body
the process by which different kinds of living organism are believed to have developed from earlier forms during the history of the earth

# data[].attributes.body
the process by which different kinds of living organism are believed to have developed from earlier forms during the history of the earth.

# data[].attributes.body
which may be transmitted to subsequent

# data[].attributes.body
the action or process of mutating.

# data[].attributes.body
eoxyribonucleic acid, a self-replicat

# data[].attributes.body
cloning is the process of producing similar populations of genetically identical indivisua

# data[].attributes.headline
If your parents are tall you will be tall

# data[].attributes.subject
If your parents are tall you will be tall

# data[].attributes.body
In humans, each cell normally contains 23 pairs of chromosomes, for a total of 46. Twenty-two of these pairs, called autosomes, look the same in both males and females. The 23rd pair, the sex chromosomes, differ between males and females.

# data[].attributes.body
deoxyribonucleic acid, a self-replicating material which is present in nearly all living organisms as the main constituent of chromosomes. It is the carrier of genetic information.

# data[].attributes.body
thread-like chain of nucleotides carrying the genetic instructions used in the growth, development, functioning and reproduction of all known living organisms and many viruses

# data[].attributes.body
V

# data[].attributes.headline
n biology, a mutation is the permanent alteration of the nucleotide sequence of the genome of an organism, virus, or extrachromosomal DNA or other genetic elements

# data[].attributes.subject
n biology, a mutation is the permanent alteration of the nucleotide sequence of the genome of an organism, virus, or extrachromosomal DNA or other genetic elements

# data[].attributes.body
Harlee Kohn

# data[].attributes.body
something thats past on to you by your parents

# data[].attributes.body
Chromosomes are Inherited From Your Parents. One chromosome from each of your 23 pairs came from each of your parents. The two chromosomes of a pair (except for the sex chromosomes) contain the same genes, but the genes have small differences.

# data[].attributes.body
the process by which different kinds of living organism are believed to have developed from earlier forms during the history of the earth.

# data[].attributes.headline
an organism or cell, or group of organisms or cells, produced asexually from one ancestor or stock, to which they are genetically identical.

# data[].attributes.subject
an organism or cell, or group of organisms or cells, produced asexually from one ancestor or stock, to which they are genetically identical.

# data[].attributes.body
Harlee Kohn

# data[].attributes.body
each of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.

# data[].attributes.body
andrew

# data[].attributes.headline
he process by which different kinds of living organism are believed to have developed from earlier forms during the history of the earth

# data[].attributes.subject
he process by which different kinds of living organism are believed to have developed from earlier forms during the history of the earth

# data[].attributes.body
Harlee Kohn

# data[].attributes.body
a thread-like structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.

# data[].attributes.body
An individual's genome is composed of two nearly identical copies: one from their mother and one from their father. This means that almost every cell contains two copies of each gene, one from each parent. In most cases, both copies of each gene are used to make protein; once made, the cell can't tell which copy of the gene any given protein molecule came from.

# data[].attributes.body
each of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.

# data[].attributes.headline
In humans, each cell normally contains 23 pairs of chromosomes, for a total of 46. Twenty-two of these pairs, called autosomes, look the same in both males and females. The 23rd pair, the sex chromosomes, differ between males and females.

# data[].attributes.subject
In humans, each cell normally contains 23 pairs of chromosomes, for a total of 46. Twenty-two of these pairs, called autosomes, look the same in both males and females. The 23rd pair, the sex chromosomes, differ between males and females.

# data[].attributes.body
Harlee kohn

# data[].attributes.body
if your parent is tall then you will be tall

# data[].attributes.body
an organism or cell, or group of organisms or cells, produced asexually from one ancestor or stock, to which they are genetically identical.

# data[].attributes.body
the process by which different kinds of living organism are believed to have developed from earlier forms during the history of the earth.

# data[].attributes.headline
Men determine the sex of a baby depending on whether their sperm is carrying an X or Y chromosome. An X chromosome combines with the mother's X chromosome to make a baby girl (XX) and a Y chromosome will combine with the mother's to make a boy (XY).

# data[].attributes.subject
Men determine the sex of a baby depending on whether their sperm is carrying an X or Y chromosome. An X chromosome combines with the mother's X chromosome to make a baby girl (XX) and a Y chromosome will combine with the mother's to make a boy (XY).

# data[].attributes.headline
Men determine the sex of a baby depending on whether their sperm is carrying an X or Y chromosome. An X chromosome combines with the mother's X chromosome to make a baby girl (XX) and a Y chromosome will combine with the mother's to make a boy (XY). 

# data[].attributes.subject
Men determine the sex of a baby depending on whether their sperm is carrying an X or Y chromosome. An X chromosome combines with the mother's X chromosome to make a baby girl (XX) and a Y chromosome will combine with the mother's to make a boy (XY). 

# data[].attributes.headline
Men determine the sex of a baby depending on whether their sperm is carrying an X or Y chromosome. An X chromosome combines with the mother's X chromosome to make a baby girl (XX) and a Y chromosome will combine with the mother's to make a boy (XY). Harlee

# data[].attributes.subject
Men determine the sex of a baby depending on whether their sperm is carrying an X or Y chromosome. An X chromosome combines with the mother's X chromosome to make a baby girl (XX) and a Y chromosome will combine with the mother's to make a boy (XY). Harlee

# data[].attributes.body
an organism or cell, or group of organisms or cells, produced asexually from one ancestor or stock, to which they are genetically identical.

# data[].attributes.headline
Men determine the sex of a baby depending on whether their sperm is carrying an X or Y chromosome. An X chromosome combines with the mother's X chromosome to make a baby girl (XX) and a Y chromosome will combine with the mother's to make a boy (XY). 

# data[].attributes.subject
Men determine the sex of a baby depending on whether their sperm is carrying an X or Y chromosome. An X chromosome combines with the mother's X chromosome to make a baby girl (XX) and a Y chromosome will combine with the mother's to make a boy (XY). 

# data[].attributes.body
Harlee kohn

# data[].attributes.body
the changing of the structure of a gene, resulting in a variant form which may be transmitted to subsequent generations, caused by the alteration of single base units in DNA, or the deletion, insertion, or rearrangement of larger sections of genes or chromosomes. like having extra limbs

# data[].attributes.body
the process by which different kinds of living organism are believed to have developed from earlier forms during the history of the earth.

# data[].attributes.body
Men determine the sex of a baby depending on whether their sperm is carrying an X or Y chromosome. An X chromosome combines with the mother's X chromosome to make a baby girl (XX) and a Y chromosome will combine with the mother's to make a boy (XY).

# data[].attributes.body
Harlee Kohn

# data[].attributes.attachment_link.readable_text
DNA is perhaps the most famous biological molecule; it is present in all forms of life on earth. But what is DNA or deoxyribonucleic acid? Here, we cover the essentials.

Virtually every cell in your body contains DNA or the genetic code that makes you you. DNA carries the instructions for the development, growth, reproduction, and functioning of all life.

Differences in the genetic code are the reason why one person has blue eyes rather than brown, why some people are susceptible to certain diseases, why birds only have two wings, and why giraffes have long necks.

Amazingly, if all of the DNA in the human body was unraveled, it would reach to the sun and back more than 300 times.

In this article, we break down the basics of DNA, what it is made of, and how it works.

What is DNA?

In short, DNA is a long molecule that contains each person's unique genetic code. It holds the instructions for building the proteins that are essential for our bodies to function.

DNA instructions are passed from parent to child, with roughly half of a child's DNA originating from the father and half from the mother.

Structure

DNA is a two-stranded molecule that appears twisted, giving it a unique shape referred to as the double helix.

Each of the two strands is a long sequence of nucleotides or individual units made of:

a phosphate molecule

a sugar molecule called deoxyribose, containing five carbons

a nitrogen-containing region

There are four types of nitrogen-containing regions called bases:

The order of these four bases forms the genetic code, which is our instructions for life.

The bases of the two strands of DNA are stuck together to create a ladder-like shape. Within the ladder, A always sticks to T, and G always sticks to C to create the "rungs." The length of the ladder is formed by the sugar and phosphate groups.

Packaging DNA: Chromatin and chromosomes

The complete set of chromosomes in a human male.
Image credit: National Human Genome Research Institute

Most DNA lives in the nuclei of cells and some is found in mitochondria, which are the powerhouses of the cells.

Because we have so much DNA ( 2 meters in each cell) and our nuclei are so small, DNA has to be packaged incredibly neatly.

Strands of DNA are looped, coiled and wrapped around proteins called histones. In this coiled state, it is called chromatin.

Chromatin is further condensed, through a process called supercoiling, and it is then packaged into structures called chromosomes. These chromosomes form the familiar "X" shape as seen in the image above.

Each chromosome contains one DNA molecule. Humans have 23 pairs of chromosomes or 46 chromosomes in total. Interestingly, fruit flies have 8 chromosomes, and pigeons have 80.

Chromosome 1 is the largest and contains around 8,000 genes. The smallest is chromosome 21 with around 3,000 genes.

What is a gene?

Each length of DNA that codes for a specific protein is called a gene. For instance, one gene codes for the protein insulin, the hormone that helps control levels of sugar in the blood. Humans have around 20,000-30,000 genes, although estimates vary.

Our genes only account for around 3 percent of our DNA, the remaining 97 percent is less well understood. The outstanding DNA is thought to be involved in regulating transcription and translation.

How does DNA create proteins?

For genes to create a protein, there are two main steps:

Transcription: The DNA code is copied to create messenger RNA (mRNA). RNA is a copy of DNA, but it is normally single-stranded. Another difference is that RNA does not contain the base thymine (T), which is replaced by uracil (U).

Translation: The mRNA is translated into amino acids by transfer RNA (tRNA).

mRNA is read in three-letter sections called codons. Each codon codes for a specific amino acid or building block of a protein. For instance, the codon GUG codes for the amino acid valine.

There are 20 possible amino acids.

What is a telomere?

Telomeres are regions of repeated nucleotides at the end of chromosomes.

They protect the ends of the chromosome from being damaged or fusing with other chromosomes.

They have been likened to the plastic tips on shoelaces that stop them from becoming frayed.

As we age, this protective region steadily becomes smaller. Each time a cell divides and DNA is replicated, the telomere becomes shorter.

In a nutshell

Chromosomes are tightly coiled strands of DNA. Genes are sections of DNA that code individual proteins.

Put another way, DNA is the master plan for life on earth and the source of the wonderful variety we see around us.

# data[].attributes.attachment_link.description
DNA is perhaps the most famous molecule on earth. Here we explain what it is, what it does, its double helix structure, and why it is so important to life.

# data[].attributes.headline
In humans, each cell normally contains 23 pairs of chromosomes, for a total of 46. Twenty-two of these pairs, called autosomes, look the same in both males and females. The 23rd pair, the sex chromosomes, differ between males and females.

# data[].attributes.subject
In humans, each cell normally contains 23 pairs of chromosomes, for a total of 46. Twenty-two of these pairs, called autosomes, look the same in both males and females. The 23rd pair, the sex chromosomes, differ between males and females.

# data[].attributes.body
Chromosomes are Inherited From Your Parents. One chromosome from each of your 23 pairs came from each of your parents. The two chromosomes of a pair (except for the sex chromosomes) contain the same genes, but the genes have small differences.

# data[].attributes.body
the action or process of mutating

# data[].attributes.body
deoxyribonucleic acid, a self-replicating material which is present in nearly all living organisms as the main constituent of chromosomes. It is the carrier of genetic information.