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The human body is made up of cells
The human body is made up of cells.
The various pieces of information recorded in these cells make up who we are as humans.
What are cells?
The cell is called the smallest unit of the living organism.
The human body is made up of skin, muscles, nerves, and various organs.
And it is cells that make up each and every one of these skin, muscles, and organs.
When viewed under a microscope, we can see that although the appearance of cells differs depending on the organ, every part is made up of a collection of tiny cells.
It all starts with just a single cell called a fertilized egg, and as it develops into a baby, the cells divide repeatedly, transforming into hundreds of different types of cells that make up various organs, creating the human body.
In other words, a single cell, a fertilized egg, will eventually divide into approximately 37 trillion cells to create a human body.
Important things inside cells
A cell is surrounded by a cell membrane.
This cell membrane contains various structures called organelles.
Organelles are divided into the nucleus and the rest of the cytoplasm.
The cytoplasm contains the endoplasmic reticulum, Golgi apparatus, mitochondria, chloroplasts, etc.
Among these, the core plays a very important role.
This is because most genes are stored in the nucleus as genetic information on chromosomes, and that information is inherited according to Mendel’s laws.
The information stored here determines the illnesses a person suffers from and their personality.
In addition to the nucleus, it is known that mitochondria and chloroplasts also have their own genes.
However, these are called extranuclear or cytoplasmic inheritance and do not follow Mendel’s laws.
Chromosomes contained within the nucleus
The nucleus contains chromosomes that contain genetic information.
Let’s take a closer look at the characteristics of this chromosome.
Chromosomes are found in the nucleus inside the cell
Living cells contain a nucleus, which contains chromosomes.
Chromosomes are normally scattered throughout the nucleus in the form of fibers called chromatin, but when cells divide, they gather together in the form of chromosomes.
The number of chromosomes varies by organism
The number of chromosomes varies depending on the organism.
For example, humans have 46 chromosomes, while cats, which are also mammals, have 38, and fruit flies have only 8.
Goldfish have 104 chromosomes, which is more than humans, and the number of chromosomes is not proportional to the size of an organism.
Each of these chromosomes is represented by a number.
Normally there are two sets of each, so there is an even number of chromosomes.
In humans, there are two sets of 23 chromosomes, meaning that there are 46 chromosomes in the cell nucleus.
Since the sperm and egg each contain one set of chromosomes, upon fertilization, the child inherits one set from the father and one set from the mother, resulting in two sets.
Of these, 44 (22 pairs) are called autosomes and 2 (1 pair) are called sex chromosomes.
Gender differences
Sex chromosomes are what determine the difference between males and females at the chromosomal level.
Each human has one set of sex chromosomes; males have one X and one Y chromosome, and females have two X chromosomes.
The mother only has an X chromosome.
Therefore, if a child inherits an X chromosome from the mother and one set including a Y chromosome from the father, the child will be a boy, and if the child inherits one set including an X chromosome, the child will be a girl.
Chromosomes are strings of DNA
Chromosomes play an important role in determining sex.
These chromosomes are made up of something called DNA.
What is DNA
DNA is an abbreviation for deoxyribonucleic acid, which refers to a nucleic acid consisting of deoxyribose (a pentose sugar), phosphate, and bases.
There are four types of bases: adenine (A), guanine (G), cytosine (C), and thymine (T). A and T are purine bases, and C and G are pyrimidine bases. Each base is called a nucleotide.
A sequence of 100 or more nucleotides linked together is called a polynucleotide.
In a single-stranded polynucleotide made up of DNA, the letters A, T, C, and G are arranged in a specific order.
This is called the base sequence.
In addition, another polynucleotide is attached to A, such as T and C, and G. DNA exists as a double-stranded nucleotide and is stored in the nucleus in a folded state.
The double-stranded nucleotides form a helical structure.
This double helix structure provides a stable structure, allowing DNA to be replicated accurately.
What is DNA for?
DNA is often referred to as the “blueprint of life.”
This is because the amino acid base sequence of DNA serves as the blueprint for proteins.
It is said that the body of a living organism is made up of approximately 100,000 types of proteins.
For example, the chromosomes inside cells are also made up of nucleic acid (DNA) and proteins.
Proteins are found in hormones, antibodies, and enzymes that are necessary to maintain bodily functions, and they are also used to maintain the structure of the body, such as the collagen found in muscles, skin, and cartilage.
In this way, proteins are used throughout the human body, both in things that can be seen and things that cannot be seen, and the blueprint for each protein is the DNA sequence itself.
DNA can develop abnormalities
DNA is so packed with various information necessary for life that it is called the “blueprint of life.”
The information stored in this DNA determines a person’s health status.
If the DNA information is fine, the recipient will be born and live a healthy life.
However, if there is some abnormality in the DNA information, there is a higher chance of being born with a disease.
There are two types of DNA abnormalities:
- Numerical abnormalities
- Structural abnormalities
Numerical abnormalities are when one or more extra chromosomes are present or one chromosome is missing.
In structural abnormalities, there is some abnormality in the chromosome itself.
For example, there are phenomena such as parts of chromosomes being missing or mistakenly joining with other chromosomes.
These chromosomal abnormalities increase the chances that a baby will be born with a disease.
This is called a “congenital disease.”
Congenital disorders include the following:
DNA abnormalities can be detected in advance using “NIPT (new type prenatal testing)”
By using NIPT (non-invasive prenatal testing ), we can investigate the likelihood that a child will be born with a disease.
It is only a matter of “what is the probability?”, so it is not possible to determine with 100% certainty.
However, NIPT (non-invasive prenatal testing) can be a great help in identifying disease risks in advance and deciding how to proceed after birth.
Of course, it is best for a fetus to be born in a healthy state.
However, in the unlikely event that there is a chromosomal abnormality, by undergoing NIPT (non-invasive prenatal testing) , a discussion can be held in advance about how to deal with the disease after birth.
For example, if NIPT (new prenatal testing) reveals a high possibility of a chromosomal abnormality, arrangements can be made smoothly for the necessary treatment.
Alternatively , even if NIPT (non-invasive prenatal testing) is not used, if another prenatal test such as an ultrasound scan reveals the possibility of a serious organ disease, it is possible to always take proactive action, such as arranging for admission to a neonatal intensive care unit immediately after birth.
Knowing about the possibility of a disease in advance will also give parents time to process their thoughts.
If you suspect that you may have an illness, you will not only be able to come to terms with it emotionally, but you will also be able to plan for the costs of treatment.
What kind of results can you get from NIPT (new prenatal testing)?
So, what specific information can we learn through NIPT (new prenatal testing) ?
The three most orthodox are:
As explained earlier, it is not possible to determine with 100% certainty whether or not a patient has the above-mentioned diseases.
It is not possible to “predict the results with certainty” with any screening test, including NIPT (new prenatal testing) .
Although it depends on the hospital where the test is performed, they do not test for all of the diseases listed above.
It is common to narrow down the presence or absence of diseases that you want to know about and then perform NIPT (non-invasive prenatal testing) to determine the possibility of having those diseases.
NIPT (new type prenatal testing) can not only determine the risk of these diseases but also the baby’s gender.
Until now, it has been possible to determine gender through ultrasound.
However, since it was a visual inspection, there was a certain possibility of making a mistake.
With NIPT (new type prenatal testing), gender is determined based on genetic information, so you can expect more accurate results than with a visual inspection.
The human body is made based on the blueprint of genes
DNA carries a variety of genetic information.
“Genes” describe how this genetic information is passed on.
What are Genes?
The inheritance of physical characteristics such as hair type, eye color, susceptibility to disease, and physical constitution from parents to children is called “genetics.”
The DNA that records the characteristics of the parents is replicated and passed on through the eggs and sperm.
A “gene” refers to a segment of DNA that carries this genetic information.
The unit of inherited information is the gene.
However, not all stretches of DNA have a genetic function.
It is known that a small percentage of DNA contains the genetic code, called genes.
In humans, each set of chromosomes contains more than 20,000 genes.
Each genetic code serves as a blueprint for a protein that has a function in the body.
Furthermore, the DNA sequence of all humans is 99.9% identical.
The remaining 0.1% of differences result in differences in hair, skin, eye color, constitution, etc.
Some traits are determined by genes.
However, as can be seen from the fact that even identical twins, who should have the same genes, can have differences in personality and appearance, there are many aspects that are influenced by lifestyle and environment.
Therefore, for example, even if a person has a genetic predisposition to cancer, it does not necessarily mean that they will develop cancer; lifestyle habits and other factors play a role in whether or not a person develops cancer.
The role of genes
Substances necessary for maintaining bodily functions, such as enzymes, hormones, and antibodies, are made from proteins.
They are made using the information contained in the DNA sequences of genes.
As explained earlier, DNA refers to a substance called “deoxyribonucleic acid” and its base sequence.
Proteins are made from this base sequence, and the proteins produced carry out functions throughout the body.
The base sequence of DNA that acts as a blueprint for proteins that function in the body is called a gene.
About the Human Genome
When talking about genes and chromosomes, it is impossible to leave out the human genome.
What is a genome?
The word “genome” is a combination of the words “gene” and “chromosome.”
A genome refers to all the DNA base sequences and genetic information, including genes, that make up a set of chromosomes.
The number of chromosomes varies from organism to organism, but the size of the genome also varies greatly from organism to organism.
The human genome contains approximately 300 million base sequences, and the organism with the largest genome is a type of amoeba.
The organism has about 100 billion base sequences.
However, just because an organism has a large genome does not necessarily mean it has a large number of genes.
This is because the base sequence of DNA does not only contain regions that function as genes, acting as blueprints for proteins.
Beyond that function, there are also parts that are unclear, such as whether there is any information or function necessary for life.
Advances in technology have made it possible for genetic information and DNA base sequences to be automatically decoded and analyzed by computer.
Since the discovery of chromosomes in 1842 and the proposal of the double helix structure of DNA in 1953, analysis of the human genome has taken place over the past 50 years.
It has a remarkable history of research, with all analysis completed in 2003.
Although we have learned a lot about chromosomes and genetics, the widespread application of the results of human genome analysis in medicine and other fields is still in its infancy.
One thing that has become more accessible through technological advances is “NIPT (new type prenatal testing).”
One of the tests that has become more accessible with the development of these technologies is the NIPT (non-invasive prenatal genetic testing ), which I introduced earlier.
It is said that a pregnant woman’s blood contains about 10% fetal DNA.
Therefore, by analyzing a pregnant woman’s blood, it is possible to examine the chromosomes and genes of the fetus.
With NIPT (non-invasive prenatal testing) , we can find out what is recorded in DNA, which is a vast treasure trove of information, before birth.
NIPT (new prenatal testing) is evolving every day
NIPT (non-invasive prenatal testing) is a prenatal test for which new testing methods are being developed day by day.
The improvement in accuracy has also been astounding.
Until now, amniocentesis and chorionic villus sampling, which have been used as prenatal diagnosis, have carried a risk of miscarriage of 1/300 to 1/100.
Although the probability is low, every parent hopes that the unlikely event never happens.
Unlike the two tests mentioned above, NIPT (non-invasive prenatal testing) can be diagnosed by simply taking about two teaspoons of blood from the mother.
Since it does not place a significant burden on the mother, the test can be performed without any major risks.
The high accuracy of the test is also cited as an attraction of NIPT (new type prenatal testing) .
There are two indices that measure the accuracy of chromosome testing:
- Sensitivity: The probability that a positive result at the test stage will remain positive after birth
- Specificity: The probability that the test is negative and that it remains negative after birth
NIPT (new type prenatal testing) has an excellent probability of detecting trisomy 21, with a sensitivity of 99.9% and a specificity of 99.90%.
This means there is a high chance of detecting abnormalities in the baby before birth.
When undergoing NIPT (new prenatal testing), do it at a time that is not too difficult for you
At Hiro Clinic, NIPT (new type prenatal testing) can be performed from approximately the sixth week of pregnancy (when pregnancy is confirmed by ultrasound examination).
Previously, some prenatal tests could only be performed after the 11th week of pregnancy.
This allows you to know the health status of your baby at an early stage.
Article Editorial Supervisor
Dr Hiroshi Oka
NIPT specialist clinic, MD
Graduated from Keio University, School of Medicine
