4.2 DNA and protein synthesis Flashcards
What is the genome?
The complete set of genetic information contained in the cells of an organism
What is the proteome?
The complete set of proteins that can be produce by a cell
Describe the structure of messenger RNA
A long, single strand. Its base sequence is complementary to the DNA it was transcribed from
Suggest advantages of using mRNA rather than DNA for translation
- Shorter and contains uracil = breaks down quickly and so no excess polypeptide forms
- Single-stranded and linear = ribosome moves along strand and tRNA binds to exposed bases
- Contains no introns
Describe the structure of transfer RNA
A single strand of around 80 nucleotides that is folded into a clover lead shape. On one end is an anti-codon, on the opposite end is an amino acid binding site
What is produced by transcription?
mRNA
Where does transcription take place?
In the nucleus
Outline the process of transcription
- The hydrogen bonds between the complementary bases break and the DNA uncoils
- One of the DNA strands is used as a template to make the mRNA molecule
- Free nucleotides line up by complementary base pairing and adjacent nucleotides are joined by phosphodiester bonds
What happens to mRNA after transcription?
In eukaryotic cells, pre-mRNA must be spliced to remove introns, leaving only the coding regions. Then it moves out of the nucleus and attaches to a ribosome
What is produced by translation?
Proteins
Where does translation take place?
In the cytoplasm (on ribosomes)
Outline the process of translation
- mRNA attaches to a ribosome and tRNA collects amino acids from the cytoplasm and carries them to the ribosome
- tRNA attaches itself to mRNA by complementary base pairing
- The amino acids attached to two tRNA molecules join by a peptide bond and then tRNA molecules detach
- This process is repeated, leading to the formation of a polypeptide chain until a stop codon is reached
