DNA
Definition: Deoxyribonucleic
acid (DNA) is the molecule that
carries genetic information for
the development and
functioning of an organism.
Location: In organisms called
eukaryotes, DNA is found inside
a special area of the cell called
the nucleus. Besides the nucleus
DNA can be found in small
amounts in mitochondria and
plastids.
Structure: DNA is made of two linked strands that wind
around each other to resemble a twisted ladder — a
shape known as a double helix. Each strand has a
backbone made of alternating sugar (deoxyribose) and
phosphate groups. Attached to each sugar is one of four
bases: adenine (A), cytosine (C), guanine (G) or thymine
(T). The two strands are connected by chemical bonds
between the bases: adenine bonds with thymine, and
cytosine bonds with guanine. The sequence of the bases
along DNA’s backbone encodes biological information,
such as the instructions for making a protein or RNA
molecule.
Structure of DNa
Function
1. Protein Production :DNA contains the instructions
needed for an organism to develop, survive and
reproduce. To carry out these functions DNA sequences
must be converted into messages(information) that can
be used to produce proteins through the process of
transcription and translation.
a. Transcription-During the process of transcription, the
information stored in a gene's DNA is passed to a similar
molecule called RNA (ribonucleic acid) in the cell nucleus
,then the MRNA(messenger RNA) carries the message,
from the DNA out of the nucleus into the cytoplasm.
b. Translation- The mRNA interacts with a specialized
complex called a ribosome, which "reads" the sequence
of mRNA nucleotides. Each sequence of three
nucleotides, called a codon, usually codes for one amino
acid.
Transfer RNA (tRNA) assembles the protein, one amino
acid at a time. Protein assembly continues until the
ribosome encounters a “stop” codon (a sequence of
three nucleotides that does not code for an amino acid).
Protein Productin in DNA
2. Replication- It is the process by which a double-
stranded DNA molecule is copied to produce two
identical DNA molecules. DNA replication is one of the
most basic processes that occurs within a cell. Each time
a cell divides, the two resulting daughter cells must
contain exactly the same genetic information, or DNA, as
the parent cell. To accomplish this, each strand of
existing DNA acts as a template for replication.
3.Mutation-Genetic mutations are changes to your DNA
sequence that happen during cell division when cells
replicate.
Mutations result either from errors in DNA replication or
from the damaging effects of mutagens, such as
chemicals and radiation, which react with DNA and
change the structures of individual nucleotides.
Genetic mutations could lead to genetic conditions like
cancer, or they could help humans better adapt to their
environment over time or may have no detectable effect.
4.Encoding information-DNA encodes information
through the order, or sequence, of the nucleotides along
each strand. Each base—A, C, T, or G—can be considered
as a letter in a four-letter alphabet that spells out
biological messages in the chemical structure of the DNA.
History
The molecule now known as DNA was first identified in
the 1860s by a Swiss chemist called Johann Friedrich
Miescher set out to research the key components of
white blood cells.
Albrecht Kossel was a
German biochemist who
made great progress in
understanding the basic
building blocks of nuclein.
In 1881 Albrecht
identified nuclein as a
nucleic acid and provided
its present chemical
name, deoxyribonucleic
acid (DNA).
Johann Friedrich Miescher
He also isolated the five nucleotide bases that are the
building blocks of DNA and RNA: adenine (A), cytosine
(C), guanine (G), thymine (T) and uracil (U).
This work was rewarded in 1910 when he received the
Nobel Prize in Physiology or Medicine.
