Download Introduction The cell`s nucleus contains DNA which carry genetic

Introduction
The cell's nucleus contains DNA which carry genetic information that determines the structure of the cell.
DNA (deoxyribonucleic acid) molecules are in the form of long strands and have a twisted spiral shape in
called a double helix. The DNA is made up of bases known as nucleotides that are attached to sugar and
phosphate molecules. Nucleotides are the units that make up the DNA structure.
Adenine pairs with Thymine
Cytosine pairs with Guanine
Each strand of DNA is bound to special proteins called histones. DNA strands are coiled around the
histones so that these long molecules can fit into a small space. In a cell that is not dividing the
coiled DNA forms a tangled network called chromatin. When a cell divides, exact copies of each DNA
molecule in the tangled mass of chromatin is distributed to the daughter cells.
Mitosis
The division of the cell in which the nucleus is divided and ensures that each body cell receives
exactly the same DNA as that possessed by the parent cell.
 Interphase: DNA molecules duplicate. Molecules form exact copies of themselves. The
quantity of DNA in the nucleus doubles between one cell division and the next. Etc etc
Protein synthesis
During interphase, the DNA molecules undergo the process of replication; form exact copies of
themselves. The two linked chains of DNA molecule separate and each separated section contains
half of the original information, which serves as a template for the nucleotides that will form in the
new half.
DNA carries genetic code which provides instructions for protein synthesis (combining of amino
acids to form large protein molecules). Protein that is made is essential for chemical reactions that
occur in the cell which are controlled by enzymes which are also proteins. Proteins are also
important as they make up most of the structural materials of cell.
The specific types of proteins that can be made are determined by genes. The order in which the
four bases (adenosine ,thymine, cytosine and guanine) occur in a DNA molecule is the genetic code.
Each of sequence of the three base is the code for a particular amino-acid.
Amino acids are assembled at the ribosomes in the cytoplasm of the cell. Instructions/information
contained in the DNA located in the nucleus must be accurately transferred to the ribosomes.
The information is gotten form the DNA to the ribosomes via the RNA (carries the message).
 RNA differs from in DNA in that it is only a single strand of sugars and phosphates and thus
the bases occurs singly. RNA also contains the base uracil (U) instead of thymine.
During protein synthesis the DNA unzips, separating its bases with the help of an enzyme.
Messenger RNA move in and take a copy of one side of the DNA strand. Then it moves out of the
nucleus heading for the ribosome. Ribosomes are organelles found attached to the endoplasmic
reticulum or surrounding the cytoplasm. They help build protein molecules from amino acids.
The messenger RNA attaches itself on to the ribosomes while the transfer RNA brings the correct
amino acid to ribosome. The three bases of messenger RNA found on the ribosome must match up
with the three bases on the transfer RNA before the right amino acid is found. The three bases on
the ribosomes are called a codon/triplet. The body has 22 different kinds of amino acids. They
combine to form a protein molecule.
Cell differentiation
It is the process in which unspecialized cells develop characteristics and functions of particular
types of cells.
Cell expansion
Multiplication or reproduction by cell division of a population of identical cells descended from a
single progenitor.
Transcription
Formation of complementary RNA.
Translation
Synthesis of RNA using a DNA molecule as the blueprint. There is a corresponding RNA
nucleotide for each DNA molecule.
 Messenger: copies info to ribosomes
 Transfer: brings amino acids from the cytoplasm to the ribosomes.