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DNA and RNA
The Molecule of Life: DNA and RNA
DNA vs. RNA Summary
DNA RNA
By comparison they both have:
Sugar phosphate background
Nitrogenous bases
By contrast each has:
Double strand, double helix
Single strand and various shapes (3)
Deoxyribose sugar Ribose sugar
A=T and C=G A=U and C=G
Stay in the nucleus Nucleus and cytoplasm
Different 5 – C sugar: Deoxyribose (DNA) and Ribose (RNA)
Thymine (DNA) and Uracil (RNA)
Thymine versus Uracil Thymine in DNA is replaced by Uracil
in RNA
vs
DNA
RNA
Ribonucleic Acid Types (p 288-295)
There are several types. We will focus on the main 3 types:
rRNA: large, makes up structure of ribosomes. - Large globular structure, forms structure with proteins to form ribosome
tRNA: smaller, contains amino acid to match code of mRNA. Compact 3-D structure
mRNA: single strand, provides complementary code from DNA for protein- Single strand may fold back on itself to form H-bonds
rRNA
rRNA: Ribosomal ribonucleic acid Located in ribosomes Provides the site on the ribosome where
the protein is assembled
rRNA Structure
This big “globular” structure is the structure for the ribosome all spread out.
A smaller “glob” provides the second part of the ribosome structure.
Ribosome: rRNA
tRNA
tRNA: Transfer ribonucleic acid In humans, more than 40 different tRNA
float freely in the cytoplasm, float to ribosome for protein synthesis
Each tRNA is connected to a different amino acid
Function: to place the correct amino acid in a protein sequence
tRNA Structure
Specific regions: 3’ end is AMINO
ACID site Anticodon is
complementary to mRNA codon (code)
tRNA detail
Typically 75 nucleotides long, twisted into a tertiary structure (3-D)
Specific in function to translation of mRNA into protein amino acid sequencing
tRNA detail
Anticodon: three nucleotide sequence that correlates to a specific amino acid that is attached to its 3’end (amazing isn’t it!)
Anticodon complements the mRNA three nucleotide sequence called the codon.
mRNA
mRNA: Messenger ribonucleic acid Long single strand of RNA that has the
coded complement from the DNA. Can fold back to form H-bonds with itself Brings the code from the nucleus to the
cytoplasm, specifically to ribosomes.
mRNA from DNA – Transcription
DNA molecule is opened at a specific gene site
mRNA is assembled complementary to one DNA strand
When coding is complete, it detaches and floats to the ribosome
DNA re-fits itself. Key enzyme: RNA Polymerase
mRNA formed at TRANSCRIPTION
Summary: 3 Main RNA Forms