RNA & Protein Synthesis Flashcards
Chapter 1.2
Define molecular gene.
A sequence of nucleotides in DNA that are transcribed to produce functional RNA. Genes code for specific polypeptide chains, proteins or an RNA molecule. They are heritable factors that control specific characteristics.
What is a locus?
The location of a gene on a chromosome.
Define genome.
The total number of genes in an organism.
Define protein synthesis.
The process in which proteins are made. It involves the transcription of a gene into mRNA, and translation of mRNA into an amino acid sequence (polypeptide chain) at the ribosomes.
Summarise the process of transcription.
Occurs inside the nucleus only:
1. Section of DNA unzips as a result of helicase breaking the hydrogen bonds between bases, exposing the bases.
2. Free-floating RNA nucleotides join to the gene’s bases on the template strand, with RNA polymerase linking complementary nucleotides. This forms an mRNA molecule.
3. The mRNA molecules leaves the nucleus through the nuclear pore.
4. DNA zips back up and is completely unaltered.
Summarise the process of translation.
Occurs in the cytoplasm:
1. mRNA attaches to a ribosome.
2. tRNA contains anti-codons, with each anti-codon corresponding with a specific amino acid which is ‘picked up’ and brought to the mRNA strand.
3. The tRNA anti-codon attaches to its corresponding mRNA codon. Ribosomes move along, processing one amino acid at a time.
4. Each amino acid attaches to the next with a peptide chain, forming a growing polypeptide chain. Each amino acid is ‘dropped off’ by the tRNA, which becomes free to collect more amino acids.
5. The last amino acid is referred to as the ‘stop’ amino acid, signifying the completion of the polypeptide chain.
6. The polypeptide chain detaches from the ribosome and folds into its specific protein shape.
Describe the features of a ribosome.
Ribosomes consist of rRNA and protein molecules, and are the sites of translation during protein synthesis. They are often found attached to the endoplasmic reticulum.
What are exons?
Sections of the DNA which are expressed (translated into proteins).
What are introns?
Sequences that are transcribed, but then cut out of mRNA.
List the order of processes that mRNA goes through to form a protein.
Transcription > splicing > translation > post-transitional modification.
How does the ribosome read the mature mRNA strand?
In the direction of 5’ to 3’ starting at the start codon AUG.
What is the role of miRNA?
It binds to mRNA in a complementary fashion to deactivate it, thus preventing the expression of that gene.
