DNA & RNA
Biology: IB Diploma Higher Level, topic 2.5.1
DNA and RNA
The two main types of nucleic acids are DNA and RNA.
What is DNA?
- Deoxyribonucleic acid (DNA) is an important information-carrying molecule.
- DNA is the genetic material in all living organisms, ranging all the way from single-celled bacteria to multicellular mammals.
- The DNA code tells the cell what to do and what proteins to make.
- The cell's entire genetic content is called its genome and the study of genomes is genomics.
Eukaryotic vs prokaryotic DNA
- In eukaryotes, DNA is found mainly in the nucleus but there is also some in chloroplasts and mitochondria.
- In prokaryotes, the DNA is not enclosed in a membranous envelope.
What is RNA?
- Ribonucleic acid (RNA) is similar to DNA.
- RNA is mostly involved in synthesising (making) proteins.
- Ribosomes are formed from RNA and proteins and are the protein builders of the cell.
The role of mRNA
- DNA never leaves the nucleus so uses messenger RNA (mRNA) to transfer genetic information to the rest of the cell.
- mRNA moves out of the nucleus to transfer information to the ribosomes. The mRNA is then used to make proteins.
Nucleic Acids
Nucleic acids carry the cell's genetic code. These are the instructions for the function of the cell. Nucleic acids are important for passing on information from generation to generation.
Components of nucleic acids
- DNA and RNA are made of monomers called nucleotides.
- Nucleotides join together to form polynucleotides.
- Polynucleotides make up nucleic acids such as DNA or RNA.
Structure of nucleotides
- Each nucleotide is formed from a pentose sugar, a nitrogen-containing organic base and a phosphate group.
- A condensation reaction between two nucleotides forms a phosphodiester bond.
- These condensation reactions happen between a sugar group on one nucleotide and a phosphate group on a different nucleotide.
DNA nucleotide
- The components of a DNA nucleotide are:
- A deoxyribose sugar.
- A phosphate group.
- An organic base - adenine (A), cytosine (C), guanine (G), thymine (T).
- The components of an RNA nucleotide are:
- A ribose sugar.
- A phosphate group.
- An organic base - adenine (A), cytosine (C), guanine (G), uracil (U).
Test yourself on DNA & RNA
What is the cell's entire genetic content called?
Where is DNA found in prokaryotes?
Which of the following is true of DNA?
Which of the following is an example of a nucleic acid?
Which of the following organic bases are found in DNA nucleotides but NOT in RNA nucleotides?