Page 43 - Cell biology PDC 2024

CHAPTER 5

DNA AND GENE EXPRESSION

Central dogma of DNA

It was first proposed in 1958 by Francis Crick, discoverer of the structure
of DNA

The central dogma of molecular biology explains the flow of genetic
information, from DNA to RNA, to make a functional product, a protein

The central dogma said that DNA has the information needed to perform
all of our proteins, and that RNA is a messenger that carries this
information to the ribosomes that are responsible for translation of the
mRNA into functional protein

The process by which the DNA information is converted into the
functional product (protein) is called gene expression

Gene expression has two main stages - transcription and translation

In transcription, the information in the DNA of every cell is converted
into mRNA that act as a message, it occurs in the nucleus.

During translation, the mRNA travel from the nucleus to the cytoplasm
where ribosomes are present to read this mRNA and make specific
proteins

The central dogma states that the pattern of information that occurs most
frequently in our cells is:

• From existing DNA to make new DNA (DNA replication)
• From DNA to make new RNA (transcription)
• From RNA to make new proteins (translation).

A DNA molecule consists of two strands that form double helix structure.
Each stand consists of nucleotides, each is composed of one of four
nitrogen-containing nucleobases (cytosine [C], guanine [G), adenine [A]
or thymine [T]), a sugar called deoxyribose, and a phosphate group

The nucleotides are joined to one another by covalent bonds (known
as the phospho-diester bond) between the sugar of one nucleotide and
the phosphate of the next, resulting in an alternating sugar-phosphate
backbone.

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