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GENETICS
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
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 strung together act as the blueprints that tell 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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DNA
A DNA strand is built of small molecules called nucleotides. There are four different types of DNA nucleotides that are called by their one letter symbols: A, T, G, and C. Thus, a piece of DNA could look something like this: AGATTCAAAAGGGCC. Human beings differ from each other only by small changes in the nucleotide structure. In the previous example, another person could have G instead of A as the first nucleotide. DNA is organized in chromosomes, of which human beings have 46 in total (23 chromosomes from both parents). The number of chromosomes and genes varies greatly between species - for example, roundworm has 13000 genes and dogs have 78 chromosomes. A human genome of 23 chromosomes contains over 3.2 billion nucleotides (A, T, G, or C) and approximately 21000 genes.
The main structure of a DNA strand is the same in every cell of the body (except for red blood cells, which do not have a nucleus and therefore lack the genome). Only the activity levels of the genes vary between different cells and tissues. Active genes produce proteins that maintain cell functions. Genes that are active in one cell type may be silent (not in use) in other cell types. Due to this characteristic, different cells can have distinct functions and form diverse structures.
CELL
Every living system consists of one or more cells. Vertebrates, including humans, are complex organisms consisting of several tissues formed by individual cells. Tissues include, for example, muscles, skin, and the nervous system.
A cell has many different parts, each with its own special function in maintaining the activities of the cell. The heart of the cell is its nucleus, which contains DNA (deoxyribonucleic acid), storing all the information needed to direct the activities of the cell.
gene
A gene is a segment of DNA that can serve as a template for a functional protein. Humans have approximately 21000 genes, and all of them are included in every cell of the body (except for red blood cells). Only approximately 2% of the whole DNA is genes. The DNA strand between the genes is used by the machinery and different proteins that are involved in activating or silencing genes.
FROM GENE TO PROTEINS
