THINK ABOUT IT
DNA is the genetic material of cells. The sequence of nucleotide bases in the strands of DNA carries some sort of code. In order for that code to work, the cell must be able to understand it, then translate it into a working reality (proteins).
An organism's genotype
- Genetic makeup (pair of genes)
- Sequence of nucleotide bases in its DNA
An organism's phenotype
- Specific traits
- Molecular basis lies in proteins and their wide variety of functions.
Lesson Overview
Fermentation
The Role of RNA
How does RNA differ from DNA?
DNA VS.
- Double stranded
- Deoxyribose sugar
- Nucleotide language
- Large polymer with millions of nucleotides
- Stays in nucleus
- Stored valuable information (heredity)
RNA
- Single stranded
- Ribose sugar
- Nucleotide language
- Short polymer 100’s of nucleotides (1 gene)
- Leaves nucleus
- Useful / temporary directions for a protein
Lesson Overview
Fermentation
Comparing RNA and DNA
The roles played by DNA and RNA are similar to the master plans and blueprints used by builders.
A master plan (DNA) has all the information needed to construct a building. Builders never bring a valuable master plan to the building site (ribosome), where it might be damaged or lost. Instead, they prepare inexpensive, disposable copies of the master plan called blueprints (mRNA).
Lesson Overview
Fermentation
3 Types / Functions of RNA
The three main types of RNA are messenger RNA
(mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA).
mRNA carries information from DNA to ribosomes in the cytoplasm.
Ribosomes are made up of several rRNA molecules and as many as 80 different proteins.
tRNA molecules transfers each amino acid to the ribosome as it is specified by the mRNA.
Blueprint
Factory
Tools
Lesson Overview
Fermentation
RNA Synthesis
How does the cell make RNA?
In transcription, segments of DNA serve as templates to produce complementary RNA molecules.
Lesson Overview
Fermentation
Transcription
In prokaryotes, RNA synthesis and protein synthesis take place in the cytoplasm.
In eukaryotes, RNA is produced in the cell’s nucleus and then moves to the cytoplasm to play a role in the production of proteins. Our focus will be on transcription in eukaryotic cells.
Transcription requires an enzyme, known as RNA polymerase, that is similar to DNA polymerase.
RNA�polymerase
Lesson Overview
Fermentation
Transcription
1) Initiation: RNA polymerase binds to a specific sequence (promoter) on the DNA and separates the DNA strands.
Promoters are signals in the DNA molecule that show RNA polymerase exactly where to begin making RNA.
Lesson Overview
Fermentation
Transcription
2) Elongation: RNA polymerase then uses one strand of DNA (3’ to 5’) as a template from which to assemble nucleotides into a complementary strand of RNA.
RNA polymerase is also directional.
Lesson Overview
Fermentation
Transcription
3) Termination: RNA polymerase reaches the terminator sequence on the DNA and disengages
Lesson Overview
Fermentation
RNA Editing
RNA molecules sometimes require bits and pieces to be cut out of them before they can go into action.
The portions that are cut out and discarded are called introns.
In eukaryotes, introns are taken out of pre-mRNA (RNA transcript) molecules while they are still in the nucleus.
The remaining pieces, known as exons(expressed), are then spliced back together to form the final mRNA.
Lesson Overview
Fermentation
Transcription
- Occurs in nucleus
- Nucleotide language
- DNA → RNA
Translation
- Nucleotide Language → Amino Acid Language
- RNA → Protein
Lesson Overview
Fermentation