Monday, March 8, 2021

Genetic Disorders

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Genes are the functional unit of Heredity. Genes are basically passed from parent to child. Genes holds DNA, instructions for making proteins. 

Some of the genes act as instructions to make molecules called protein.

 However, many genes don't code for proteins. Genes differ in size from a few hundred DNA bases to more than 2 million bases in humans. 

In humans, genes are between 20,000 and 25,000.

Where do genes come in? 

Genes are made up of DNA, DNA contains 4 chemicals A, T, C and G i.e. adenine, thymine, cytosine and guanine respectively. These chemicals are strung in patterns on extremely thin coiled strand in the cell. 

They pass this genetic information to the new cells, as the cells duplicate.

Basically DNA is wrapped together to form structures called chromosomes.

 There are total 46 chromosomes present in the cell of a human body, i.e. 23 pairs of chromosomes. 

Egg cells and Individual sperm, however, have just 23 unpaired chromosomes. 

We received half of our chromosomes from father's sperm cell and half from mother's egg. 

A female’s child gets an X chromosome from each parent; a male child receives an X chromosome from his mother and a Y chromosome from his father.

Genes are integrant of DNA that are carried on the chromosomes and determine specific human characteristics, such as height or hair color. Because we have a pair of each chromosome, we have two copies of every gene.


Heredity is the passing of genes from one generation to the next generation. We inherit our parents' genes. 

Heredity helps to make you the person you are today: tall or short, with black hair or blond, with brown eyes or blue or black.

Can our genes determine whether we'll be a straight-A student or a great athlete? 

Heredity plays an important role, but our environment also influences our interests and abilities.

A person can have mutations in a gene that can cause many issues for them. Sometimes changes cause little differences, like hair color or eye color.

 Other changes in genes may cause health problems.

Changes in a gene usually end up causing that particular gene copy to not do its job the way it normally should. 

As we have two copies of every gene, typically there's still a "normal" working copy of the gene. 

In these cases, usually nothing out of the ordinary happens since the body can still do the jobs it needs to do, i.e. example of an autosomal recessive trait.

For someone to have a heredity disease or characteristic, the person must have a gene variation in both copies of the gene pair, causing the body to not have working copies of that particular gene.

Genes can be either dominant or heredity

Even if there is just one variation in one copy of that gene pair; the one variation 'dominates' the normal back-up copy of the gene, and the characteristic shows itself, Dominant genes show their effect.

A person can be born with gene variations, or they can happen over a lifetime. 

Variations can occur when cells are aging or have been exposed to certain chemicals or radiation. 

Thankfully, cells usually recognize these types of mutations and repair them by themselves. 

Other times, they can cause diseases, such as some types of cancer.

If the gene variation exists in sperm cells or egg, children can inherit the gene mutation from their parents. 

When the change is in every cell of the body, the body is not able to 'repair' the gene change.


There are more than 4000 diseases caused by mutations. 

But having a gene-transmitted disease that may cause a disease or condition doesn't always mean that a person will actually develop that disease or condition.

People carry from 5 to 10 genes with mutations in each of their cells on an average. 

Generally, Problems are faced when the particular gene is dominant or when a mutation is present in both copies of a recessive gene pair. 

Problems can also face when several variant genes interact with each other — or with the environment — to increase susceptibility to diseases.

If a person has a variation in a dominant gene which is associated with a particular condition, he or she will usually have features of that condition.

 And, each of the person's children will have a 50% chance of inheriting the gene and developing the same features.

 Diseases and conditions caused by a dominant gene include achondroplasia (a disorder of bone growth that prevents the changing of cartilage to bone), Marfa syndrome (a genetic disorder that affects the connective tissue) and Huntington disease (a progressive brain disorder that causes uncontrolled movements, emotional problems, and loss of thinking ability).

People who have an evolution in just 1 copy of a recessive gene are called 'carriers'. People don't usually have the disease because they have a normal gene copy of that pair that can do the job. 

When two carriers have a child together, however, the child has 25% chance of getting a gene with a mutation from both parents, which would result in the child having the disease.  

Cystic fibrosis (a hereditary disease that affects the lungs and digestive system), sickle cell anemia (an inherited red blood cell disorder in which there aren't enough healthy red blood cells to carry oxygen throughout your body), and Tay-Sachs disease (a genetic disorder that results in the destruction of nerve cells in the brain and spinal cord) are caused by recessive variation from both parents coming together in a child.

With inactive gene variation on the X chromosome, usually only boys can develop the disease because they have only 1 X chromosome. 

Girls have 2 X chromosomes — since they have a back-up duplicate of another X chromosome, they don't always show features of X-linked conditions. 

These include the color blindness, bleeding disorder and hemophilia (genetic disorder that impairs the body's ability to make blood clots, a process needed to stop bleeding).

Sometimes, when sperm unite and an egg, the new cell gets too many or too few chromosomes, which can cause issues for the child.





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