Genetics is the study of
heredity. Heredity is a biological process where a parent passes certain genes
onto their children or offspring. Every child inherits genes from both of their
biological parents and these genes in turn express specific traits. Some of
these traits may be physical for example hair and eye color and skin color etc.
On the other hand some genes may also carry the risk of certain diseases and
disorders that may pass on from parents to their offspring.
Genes
in the cell
The
genetic information lies within the cell nucleus of each living cell in the
body. The information can be considered to be retained in a book for example.
Part of this book with the genetic information comes from the father while the
other part comes from the mother.
Chromosomes
The
genes lie within the chromosomes. Humans have 23 pairs of these small
thread-like structures in the nucleus of their cells. 23 or half of the total
46 comes from the mother while the other 23 comes from the father.
The
chromosomes contain genes just like pages of a book. Some chromosomes may carry
thousands of important genes while some may carry only a few. The chromosomes,
and therefore the genes, are made up of the chemical substance called DNA
(DeoxyriboNucleic Acid). The chromosomes are very long thin strands of DNA,
coiled up tightly.
At
one point along their length, each chromosome has a constriction, called the
centromere. The centromere divides the chromosomes into two ‘arms’: a long arm
and a short arm. Chromosomes are numbered from 1 to 22 and these are common for
both sexes and called autosomes. There are also two chromosomes that have been
given the letters X and Y and termed sex chromosomes. The X chromosome is much
larger than the Y chromosome.
Chemical
bases
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The
genes are further made up of unique codes of chemical bases comprising of A, T,
C and G (Adenine, Thymine, Cytosine and Guanine). These chemical bases make up
combinations with permutations and combinations. These are akin to the words on
a page.
These
chemical bases are part of the DNA. The words when stringed together act as the
blueprints that tells the cells of the body when and how to grow, mature and
perform various functions. With age the genes may be affected and may develop
faults and damages due to environmental and endogenous toxins.
Males
and females
Women
have 46 chromosomes (44 autosomes plus two copies of the X chromosome) in their
body cells. They have half of this or 22 autosomes plus an X chromosome in
their egg cells.
Men
have 46 chromosomes (44 autosomes plus an X and a Y chromosome) in their body
cells and have half of these 22 autosomes plus an X or Y chromosome in their
sperm cells.
When
the egg joins with the sperm, the resultant baby has 46 chromosomes (with
either an XX in a female baby or XY in a male baby).
Genes
and genetics
Each
gene is a piece of genetic information. All the DNA in the cell makes up for
the human genome. There are about 20,000 genes located on one of the 23
chromosome pairs found in the nucleus.
To
date, about 12,800 genes have been mapped to specific locations (loci) on each
of the chromosomes. This database was begun as part of the Human Genome
Project. The project was officially completed in April 2003 but the exact
number of genes in the human genome is still unknown.
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