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Powerpoint Presentation: The Nucleic Acids

 

Molecular Genetics Index

The Chemical Nature if the Gene
The Gene
Ribonucleic Acid (RNA)
The Characteristics of the Genetic Code
The Genetic Code
Gene Expression
Translation
The lac Operon
Gene Mutations
Genetic Engineering
Electrophoresis

Topic Chapters Index

 

ADN animation

By brian0918™ (Own work) [Public domain],
via Wikimedia Commons

 

The DNA is made from two strands of polynucleotide

  • The sister strands of the DNA molecule run in opposite directions (antiparallel).

  • They are joined by the bases.

  • Each base is paired with a specific partner

  • A is always paired with T

  • C is always paired with G

  • This the sister strands are complementary but not identical

  • The bases are joined by hydrogen bonds, individually weak but collectively strong.

DNA model

 

MOLECULAR GENETICS

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The Nucleic Acids

First isolated by Friedrich Miescher in 1869.
He isolated what he called nuclein from the nuclei of pus cells.
Nuclein was shown to have acidic properties, hence it became called nucleic acid

 

Two types of nucleic acid are found

  • Deoxyribonucleic acid (DNA)

  • Ribonucleic acid (RNA)

 

The distribution of nucleic acids in the eukaryotic cell is interesting

DNA is found in the nucleus with small amounts in mitochondria and chloroplasts.

RNA is found throughout the cell.

 

DNA as genetic material: The circumstantial evidence

  1. It is present in all cells and virtually restricted to the nucleus.

  2. The amount of DNA in somatic cells (body cells) of any given species is constant (like the number of chromosomes). The RNA content varies a lot.

  3. The DNA content of gametes (sex cells) is half that of somatic cells. In cases of polyploidy (multiple sets of chromosomes) the DNA content increases by a proportional factor.

  4. The mutagenic effect of UV light peaks at 253.7nm. This is the peak for the absorption of UV light be DNA.

 

The Nucleic Acid Structure

Nucleic Acid Structure

 .

Ribose and deoxyribose

These are pentose sugars. They have 5 carbons

Pentose sugar

ribose and deoxyribose sugars

 

The sugar-phosphate backbone of polynucleotides

The nucleotides are all orientated in the same direction. The phosphate group joins the 3rd Carbon of one sugar to the 5th Carbon of the next in line.

The sugar-phosphate backbone of polynucleotides

Adding in the bases

The bases are attached to the 1st Carbon.
Their order is important. It determines the genetic information of the molecule.

the DNA backbone

 

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