2.7 & 7.2 Protein Synthesis: Transcription Flashcards
What is the importance of transcription and translation?
Transcription and translation is protein synthesis and is the expression of genes.
How is RNA used in translation?
As a messenger and translating molecule.
Distinguish between the sense and antisense strands in DNA.
The mRNA strand is complementary to the antisense strand. The antisense strand is also known as the template strand, as it is used for transcription, to make mRNA. mRNA corresponds with the antisense strand, with the exception of the base T, which is replaced with U. mRNA is complementary to the sense strand.
Outline transcription.
- RNA polymerase binds to a site on the DNA at the start of a gene.
- RNA polymerase moves along the gene, separating DNA into single strands and pairing up RNA nucleotides with complementary bases on one strand of DNA
- RNA polymerase forms covalent bonds between RNA nucleotides
- The RNA separates from the DNA and the double helix reforms
- Trasncription stops at the end of the gene and the completed mRNA molecule is released
Why is it necessary to regulate the expression of genes?
Some proteins only need to be produced at certain times and in certain amounts, meaning their gene expression needs to be regulated.
How are genes regulated in prokaryotes?
Gene expression is regulated as a result of various environmental factors.
Differentiate between enhancers, silencers, promoters, and promoter-proximal elements.
Enhancers: regulatory sequences on the DNA which increase the rate of transcription when proteins bind to them
Silencers: Sequences on the DNA which decrease the rate of transcription when proteins bind to them
Promoters: DNA sequences located on the 5’ region adjacent to the transcriptional start site. RNA polymerase and accessory proteins bind to the promoter to initiate production of an mRNA transcript.
Promoter-proximal element: Nearer to the promoter and binding to them is necessary to initiate transcription.
What is the result of the methylation, acetylation, or phosphorylation of histones?
Promotion or inhibition of transcription.
What is the effect of direct methylation of DNA?
Decreased gene expression
In which direction does transcription occur?
5’ to 3’
Outline splicing.
Introns do not affect the formation of the polypeptide and so are removed. The spliceosome breaks the intron away from the extrons which then bind together to form mature mRNA.
What are some post transcriptional modifications apart from splicing? What are their functions?
5’ Cap: Ensures mRNA stability by preventing breakdown
Poly A Tail: protects mRNA in nuclear export, translation, makes it more stanle
Where does transcription take place?
The nucleus
What happens to the mRNA after it is matured?
It is sent outside of the nucleus to a ribosome.
