D1.2 Flashcards
Protein Synthesis
Define transcription
The synthesis of RNA using a DNA template
List the roles of RNA polymerases in the process of transcription
-synthesises RNA from a DNA template
-creates an RNA copy of a segment of DNA
Distinguish between the sense and antisense strands of DNA
One strand of DNA is called the sense strand because when you read it in the right direction it provides the code to make a protein. In two-stranded DNA, the sense strand is bonded to an opposite DNA strand which is called the antisense or noncoding strand.
Outline how the stability of information stored in DNA is maintained
Cells contain protection systems such as antioxidants that eliminate damaging metabolites before causing extensive damage to the DNA
Define gene expression
Gene expression is where the gene is “turned on” and used to synthesise a functional gene product (protein) and ultimately a phenotype.
Outline the major steps of gene expression
Transcription and Translation
DNA → mRNA → polypeptide
What is the central dogma of Molecular biology?
A theory stating that genetic information only flows in one direction, from DNA to RNA, to protein, or RNA directly to protein
Outline the role of transcription in regulating gene expression
Before RNA polymerase can bind to the promoter region for a particular gene transcription factors must first bind to the promoter. Together they form a transcription initiation complex that allows for transcription of a gene.
Define translation
The first step in gene expression. Involves copying a genes DNA sequence to make an RNA molecule in order to construct a functional product (protein)
State the location of translation in cells
Ribosomes
Outline the roles of mRNA, ribosomes and tRNA in translation.
Messenger RNA (mRNA) molecules carry the coding sequences for protein synthesis and are called transcripts; ribosomal RNA (rRNA) molecules form the core of a cell’s ribosomes (the structures in which protein synthesis takes place); and transfer RNA (tRNA) molecules carry amino acids to the ribosomes during protein
Describe the structures of mRNA and tRNA
mRNA has a linear structure and carries genetic information copied from DNA. tRNA has an L shaped 3D structure.
State the complementary base pairing utilised in translation
tRNA molecules recognise the codons in the mRNA through base pairing between codon and anticodon. The pairing ensures the correct amino acid based on the mRNA sequence is added to the polypeptide chain.
Define codon and anticodon
A codon is a three-nucleotide sequence found on mRNA that codes for a certain amino acid during translation. The anticodon is a three-nucleotide sequence found on tRNA that binds to the corresponding mRNA sequence.
Describe the formation of hydrogen bonds between codon and anticodon.
The bonds between the anticodon of a tRNA molecule and the complementary codon of mRNA are hydrogen bonds that form while the codon is in the A site. This so happens in the ribosomal unit when a tRNA approaches the mRNA for bonding. The nitrogenous bases present in codon and anticodon bond together by hydrogen bonds.
