57 WJEC Biology AS Level - Study And Revision Guide - Neil Roberts (1.5 Nucleic Acids And Their Functions) Flashcards
Draw a diagram of transcription?
Why is pre-mRNA spliced in eukaryotes?
In eukaryotes, introns (non-coding regions) are present within many genes.
They are also transcribed producing pre-mRNA.
The coding regions are referred to as exons.
The pre-mRNA is spliced to remove the non-coding regions before passing to the ribosomes.
Why is there no splicing of pre-mRNA in prokaryotes?
In prokaryotes, the DNA does not contain introns.
Hence the mRNA is produced directly from the DNA template.
What RNA molecule does translation involve?
Translation involves another specific RNA molecule called transfer RNA (tRNA).
What is there at the two ends of the tRNA molecule?
At one end of the tRNA molecule there are three exposed bases called the anticodon.
These bases are complementary to the mRNA codon.
At the opposite end of the tRNA molecule is an amino acid attachment site where the relevant amino acid is found.
What is amino acid activation?
The attachment of the relevant amino acid to the attachment site is called amino acid activation and requires ATP.
What does translation involve?
Translation involves converting the codons on the mRNA into a sequence of amino acids known as a polypeptide.
What is each ribosome made up of?
Each ribosome (found free in the cytoplasm, or attached to the rough endoplasmic reticulum) is made up of two subunits made from ribosomal RNA and protein.
Where does the mRNA and tRNA bind to, in the ribosome?
The mRNA binds to the smaller subunit, whilst tRNA binds to one of two attachment sites on the larger subunit.
What is important to keep in mind regarding DNA polymerase and RNA polymerase?
Don’t get DNA polymerase and RNA polymerase mixed up!
Introns (Key-Term)
Non-coding nucleotide sequence in DNA and pre-mRNA, that is removed from pre-mRNA, to produce mature mRNA.
Exons (Key-Term)
Nucleotide sequence on one strand of the DNA molecule and the corresponding mRNA that codes for the production of a specific polypeptide.
