A set of instructions that controls the way our body works and develops. They are stored as a four-letter code by the DNA molecule.
Each molecule is wound like a thread around balls of protein to form nucleosomes, which are arranged to form a thick cord. This cord is coiled around to form a thicker cord, and then coiled up again. The end result is a chunky, X-shaped structure called a chromosome.
Genome:
Half our genes came from father and half genes came from mother. These two sets joined to form a complete set, genome, with a maternal and a paternal version of every gene.
Our genome controls most of our physical characteristics.
DNA (Deoxyribonucleic acid):
DNA is a molecule composed of two polynucleotide chains that coil around each other to form a double helix carrying genetic instructions for the development, functioning, growth and reproduction.
Structure of DNA molecule:
The two DNA strands are known as polynucleotides as they are composed of simpler monomeric units called nucleotides.
Nucleotide:
Nucleotide is composed of:
1. One of four Nitrogen-containing nucleobases.
2. A sugar called Deoxyribose.
3. A Phosphate group.
The four bases (Nitrogen-containing nucleobases):
• Adenine (A)
• Guanine (G)
• Cytosine (C)
• Thymine (T)
Backbone of DNA:
The backbone of DNA is made of alternating sugar and phosphate units joined in a chain by covalent bonds (known as the phospho-diester linkage).
Base pairs:
The nitrogenous bases of the two separate polynucleotide strands are bound together (A - T and C - G) with hydrogen bonds to make double-stranded DNA.
A - T : Adenine always pairs with Thymine.
C - G : Cytosine always pairs with Guanine.
DNA Packaging:
Numbers:
1 The number of DNA molecules in a chromosome.
46 The number of Chromosomes in the nucleus of each cell.
300+ The number of times, DNA would stretch to the Sun and back to the Earth, if we took the DNA from all the cells and connected end to end.
Basics of the Human Body:
• Atoms and molecules:
The smallest individual parts in the body.
Example: DNA molecule.
• Cells:
Tiny living, basic units of life.
There are 75 trillion cells in the human body.
Cells do specific jobs.
Example: Nerve cells conduct nerve impulses.
• Tissue:
Group of structurally and functionally similar cells.
Example: Cardiac muscle tissue found in the heart.
• Organ:
Tissues join together to form organs.
They perform specific job.
Example: Heart
• Organ System:
Organs work together in systems.
Example: The heart, blood vessels and the blood are the parts of the circulatory system.
