All About Hypothyroidism

 

DNA is made up of two long chains of nucleotides. Nucleotides are made up of a phosphate group, a five-carbon sugar molecule and one of the four different nitrogenous bases. The nitrogenous bases, Adenine (A), Thymine (T), Guanine (G) and Cytosine (C) participate in complimentary base pairing. Adenine (A) pairs with Thymine (T) while Guanine (G) pairs with Cytosine (C). The sequence of the base pairing determine the information available for constructing and maintaining an organism. DNA is double helix much like ladder, with the sugar and phosphate molecules as the backbone of the helix and nitrogenous base pairs as the rungs.

 

Replication of DNA

 

The most important characteristic of DNA is that DNA can be replicated through the process of DNA replication. DNA replication is the process of producing two identical copies of one DNA molecule from a parent cell. DNA replication is semiconservative – meaning that each strand of original DNA serves as a template strand to produce the complementary strand.

DNA replication occurs in three basic steps:

• Separating the DNA structure

• Construction of the complementary strand

• Quality control and DNA repair

 

DNA replication begin with an enzyme called DNA helicase. DNA helicase unwind the DNA double helix by separating hydrogen bonding and complementary base pairs. Single strand binding proteins (SSBs) temporarily bind to each strand to keep the complementary base pairs separated because they tend to anneal. Another enzyme, DNA gyrase come and relieve the tension that was caused by the DNA unwinding. After, DNA polymerase III synthesize the complementary strands of DNA. One of the strand are synthesized continuously while the other strand is synthesized in fragments. DNA ligase seals the fragments by catalyzing the formation of phosphodiester bonds. After the building of the complementary strands, DNA polymerase I and II go over the two strands of DNA and check for errors. This process is called proofreading. After proofreading, you have two new copies of one DNA molecule.

 

Transcription and Translation

 

The DNA that is make up of human genome can be divided in subdivisions called genes. Each gene performs a specialized function and encodes for a unique protein. DNA is transcribed from DNA to mRNA and then translated from mRNA to a polypeptide.

 

Transcription is the synthesis of mRNA from a DNA template. mRNA is similar to the DNA molecule but differs in one the nitrogenous bases. mRNA has base uracil (U) which replaces thymine (T).

 

Translation is the synthesis of protein from an mRNA template. Ribosomes read the mRNA strand and translate the mRNA strand into amino acid sequence. Each three-nucleotide codon specifies for a particular amino acid. Each of amino acid join together to create a polypeptide which is a protein.

 

Mutations

 

Mutations are permanent changes in the DNA sequence that are inherited. Some mutations have negative side effects, positive side effects or no effect to the DNA sequence. Mutations range in size; some mutations affect a single base pair while other can affect a whole segment of a chromosome with multiples genes