Lecture 17 Flashcards
What is the central dogma of biology? What stages does it have?
The central dogma of biology is an explanation of genetic information within a system. Its stages are the DNA(information) is used to produce RNA (messenger) via transcription or RNA is used to produce DNA via reverse transcription. Finally the RNA is used to produce the protein(worker).
What is a gene? What may the sequences do?
A gene is a defined region(sequence) of DNA that produces a diffusible product (RNA) that has some function. This gene may contain sequences responsible for regulation of synthesis of the diffusible product, production of the diffusible product, or responsible for the further processing of the diffusible product..
What is transcription? which strand is used for this?
Transcription is the process used to produce RNA from DNA, it is catalysed by the enzyme RNA polymerase which synthesises the mRNA through catalyzation of phosphodiester bonds between the ribonucleotides and the selection of the correct nucleotides based on the DNA sequence. The mRNA is made from the template strand, causing it to be a copy of the coding strand (the template strand runs in the 3’ -5’ direction.
What are other possible names for the coding and noncoding strand? What is the transcript?
coding strand is the sense strand, non coding strand is the antisense strand or the template strand. A transcript as it applies to biology is a newly synthesised RNA sequence.
What are the three stages of transcription?
Initiation, elongation and termination.
What is initiation in regards to mRNA synthesis? How does it occur?
Initiation is the start of mRNA synthesis, it is regulated by specific sequences of the DNA. It starts with transcription factors binding to the TATA (High A and T occurence) box and other regions of the promoter, the RNA polymerase II then binds to this promotor region and forms a transcriptional initiation complex with the transcription factors, the two DNA strands then seperate and the RNA polymerase II starts mRNA synthesis without need for a primer.
What is elongation as it applies to mRNA synthesis?
RNA polymerase II uses the template strand as a template and inserts complementary RNA nucleotides in the 5’ -> 3’ direction.
What is the anatomy of prokaryotic genes? Which regions are lost in each step?
The DNA consists of a promoter region a coding sequence as well as 5’ and 3’ untranslated regions (5’ and 3’ UTR) on either side of the coding sequence. Once transcribed into mRNA the promotor region is lost, leaving only the coding sequence as well as the 5’ and 3’ UTR. During translation the UTR tegions are also lost, leaving only the coding sequence in the final protein.
What is different about the anatomy of eukaryotic and prokaryotic genes?
The eukaryotic genes have additional regulatory sequences before the promoter region and after the 3’UTR, after transcription the 5’UTR has the 5’G cap and the 3’ UTR has a poly A tail (many As). These 5’ G caps and 3’ poly A tail both act to prevent mRNA degradation by enzymes, regulate translation, regulate nuclear export. Additionally the G cap does the regulation of translation by providing a ribosome recognition and binding site and also promotes intron excision. The coding sequence also contains exons and introns.
What is standard splicing?
Standard splicing refers to the removal of the introns (non coding regions of coding sequence) from the precursor mRNA following transcription.
What are the coding regions of the coding sequence called? What about the non coding? Are the UTR regions part of the exons? what happens to them?
Coding: exons, non coding: introns, The UTR regions are part of the exons (5’ will be with exon 1, 3’ will be with exon 4), The UTR regions are however lost during translation into proteins.
What can occur from mutations in non coding regions?
Mutations to the non coding regions may disrupt the normal gene expression, even if they are not directly in the protein.
What processes can be used to produce multiple different proteins from one gene?
alternative splicing: The exclusion of particular exons during splicing of the pre-mRNA.
Posttranslational modifications: E.g polypeptide processing (exclusion of particular regions in the translated immature protein chain), chemical modification (attachment of biochemical groups to change the function and activity of the protein).
What are the locations of transcription and translation in eukaryotics and prokaryotics? Are the processes coupled or seperate? What does this mean?
eukaryotics do transcription in the nucleus, translation in the cytoplasm and the two are not coupled (mRNA is fully formed before translation). Prokaryotics do both transcription and translation in the cytoplasm, the processes are coupled (transcription and translation occur at the same time).
