DNA- Transcription And Translation Flashcards
Gene
A section of DNA that codes for the amino acid sequence of a polypeptide and functional RNA.
Locus
The fixed position on a DNA molecule that a gene occupies.
Genome
A complete set of genes in a cell.
Proteome
A complete set of proteins that a cell can produce.
Transcription
It is the production of mRNA from DNA.
DNA helicase causes the hydrogen bonds between the bases to break and causes the DNA strand to unwind. One strand of the DNA acts as a template. RNA nucleotides are attracted to the exposed bases and bind with their complementary pairs. RNA polymerase then moves along the template strand causing the RNA nucleotides to join to each other. The DNA rewinds behind as the RNA detaches. The RNA polymerase will stop when it reaches a stop triplet code.
The pre-mRNA is then formed.
Splicing in eukaryotes
The DNA has introns which are non-coding.
These introns are removed from the pre-mRNA to make mRNA.
This is called splicing.
Mutations
There are changes in the sequence of bases in the DNA.
They can change the order of amino acids and therefore the hydrogen/ionic/disulphide bonding.
This means there is a change in tertiary structure of the polypeptide.
This is often linked to how enzymes function.
Mutations - how they make non-functional proteins
The amino acid sequence is changed
There is a change in hydrogen/ionic bonds
The tertiary structure is altered and therefore so is the shape of the active site
No enzyme-substrate complexes can be formed.
Triplet code
Each amino acid is coded for by three bases.
Some amino acids have more than one triplet coding making them degenerate. Some bases act as stop codons.
The code is universal and non-overlapping so each base is only part of one triplet.
Some sections of a gene are non-coding (introns), while others are coding (exons).
