In
1860s an Austrian scientist named Gregor Mendel, while experimenting with pea
plants, discovered how traits are transmitted from parents to offspring. This
discovery laid the foundation for modern genetics, the study of genes and their
role in inheritance.
The
three major macro-molecules essential for all known forms of life are Nucleic Acids,
proteins and carbohydrates. A gene is the basic unit of heredity information
located in the chromosome of the nucleus of the cell. A chromosome consists of
a long strand of DNA containing many genes. Genes are made up of
deoxyribonucleic acid (DNA) which stores genetic information and encodes
(carries) the instructions for proteins that direct the activities of cells and
functions of the body. Most DNA molecules consist of two strands coiled around
each other to form a double helix. Ribonucleic Acid (RNA) is similar to DNA but
it is single stranded and transfers the genetic information obtained from DNA
to the proper location for protein synthesis.
Genes
control how a cell functions, including how quickly it grows, how often it
divides, and how long it lives. To control these functions, genes produce
proteins that perform specific tasks and act as messengers for the cell. That’s
why it is essential that each gene have the correct instructions or “code” for
making its protein so that the protein can perform the proper function for the
cell. There are approximately 20,000 to 25,000 genes in each person’s genetic
makeup, or genome. Every cell in a person’s body has the same DNA. If all of
the DNA in our body were connected, it would stretch about 67 billion miles! Genes
direct cells to make proteins and guide almost every aspect of operation and
repair of cells.
A
person’s genes can have a profound impact on health and disease. More than 4000
diseases are thought to be related to altered genes. Genomics is the study of
all of a person’s genes (the genome), including interactions of these genes
with each other and with the person’s environment. Genomic factors play a role
in the leading causes of death in the United States including heart disease,
cancer, diabetes mellitus, stroke, and Alzheimer’s disease. These diseases are
typically caused by a combination of genetic and environmental factors.
Any
change in the usual DNA sequence is called a mutation. Subtle or simple
variations in DNA are called polymorphisms (many forms) which account for
slight variations among people such as hair and eye color. However, some gene
variations may result in disease or an increased risk for disease. The change
in gene structure may alter the type and/or the amount of protein
produced.
Genetic
mutation can be inherited or can occur during cell division, DNA replication,
and from environmental factors like UV radiations leading to skin cancer. Toxins
in cigarettes, and also in chemotherapy which also targets the healthy cells.
Cells have built-in mechanisms that catch and repair most of the changes that
may happen but as we age the DNA repair does not work as before and changes
accumulate.
Genetic
disorders can be prevented or treated by gene therapy approaches which include
but may not be limited to the following:
Replacing a mutated gene with healthy copy
of the gene.
Inactivating a mutated gene that is functioning
improperly
Introducing a new gene into the body to
help fight a disease through a viral vector
Stem cell therapy which allows for
regeneration of lost tissue and restoration of function in various diseases.
CRISPER/Cas9 and targeted gene editing is
now widely used in different cell types and organisms and has potential
applications in human gene therapy.
·
Sources
Sharon
L. Lewis, et al.
Pathophysiologic
Mechanisms of Disease
Genetics
and Genomics 2014
Genetic-Science-The
Guardian
Nicola
Davis
New
research about Alzheimer’s Disease 2016
Wikipedia
