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