A detailed summary of DNA and RNA Structure and Coding. This includes definitions, the roles of the people who discovered the structure of DNA, where DNA is found, the structure of DNA, and the similarities and differences between DNA and RNA.
DNA STRUCTURE AND CODING
Watson and crick – protein synthesis and DNA replication
Structure and location of DNA and RNA (mRNA and tRNA only)
Structure of nucleotides – four nitrogenous bases
Mitochondrial DNA
Nucleic acids: have the capacity to store information that controls cellular activity and the
development of an entire organism. They do this by controlling the synthesis of proteins.
Proteins make up much of the structure of the body and, because enzymes are proteins,
they control the chemical processes inside cells.
The two nucleic acids are:
1. Deoxyribonucleic acid (DNA)
2. Ribonucleic acid (RNA)
Deoxyribonucleic acid –DNA
Who discovered the structure of DNA?
Maurice Wilkins and Rosalind Franklin – X-ray of DNA
Francis Crick and James Watson
- Built a model of DNA
- Developed ideas about genetic replication:
A=T and C=G – determines that given a sequence of bases in one strand, the
other strand will be automatically determined
Where is DNA found?
In the chromatin network in the nucleus
Chromatin: chromosomal material made up of DNA, RNA and histone proteins as found in a
non-dividing cell
The DNA molecule is coiled so that these long structures can fit inside the
nucleus
Extracellular DNA: small amounts of DNA found
outside the nucleus in mitochondria in plants and
animals and in the chloroplast in plants.
Units that make up DNA:
Polymer = long chain
Monomers = small units
Nucleotides = building blocks
Deoxyribose = sugar molecule (S)
Phosphate molecule (P)
, Nitrogenous bases – the foundation of the genetic code, instructing cells on how
to synthesise enzymes and other proteins
Adenine
Thymine
Guanine
Cytosine
- The bonds between the sugar and phosphate molecules are strong
- Pairs of bases linked by weak hydrogen bond
Always:
A=T or A=U
C=G
Purines: Guanine and Adenine – two fused rings of nitrogen, carbon and hydrogen atoms
Pyrimidines: Thymine, Cytosine and Uracil – one ring of similar atoms and are therefore
much smaller than purines
It is the sequence of the nucleotides (bases) that determines the genetic code of an
organism
The role of DNA:
Carry hereditary information in each cell in the form of genes
Provide a blueprint for an organisms growth and development by coding for protein
synthesis
Can replicate so that the genetic information is passed on to each daughter cell
formed during cell division
Non-coding DNA:
The non-coding regions were thought to be “evolutionary junk” but they are now
known to form functional RNA molecules which have regulatory functions
Protein-coding regions of a DNA molecule are called exons and they are interrupted
by the non-coding regions called introns
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