TRANSCRIPTION Flashcards
how do genes work?
cells and living things made from the instructions in DNA
- DNA, proteins, cells
what is gene regulation?
ability to control cell’s level of gene expression
why are genes regulated?
so proteins can be produced at certain times and in specific amounts
benefits of gene regulation?
conserves energy and ensure genes are expressed in the appropriate cell type and at the current stage in the development
what is transcription?
- making RNA copy of a single gene
- copies DNA into RNA
what is gene expression?
information from a gene is used in the synthesis of a functional gene product (protein synthesis)
- DNA makes RNA, RNA makes protein
how are proteins manufactured?
DNA acts as a template for making RNA, which in turn acts as a template for the manufacture of proteins
where does transcription occur?
takes place in the nucleus
how do cell know which gene to express?
Ligand (signals) bind to specific receptor of the cells which trigger signal transduction (signalling pathway) to activate target proteins which serve as transcriptional factors
what enzyme is used to perform transcription?
RNA polymerase
what substrates are used in RNA synthesis?
ATP, CTP, GTP, UTP
which is the transcribed strand?
template strand or antisense strand
which is the non-transcribed strand?
coding strand or sense strand
RNA is complementary to what strand?
template or antisense strand
what strand has the same sequence of as RNA?
DNA coding strand or sense strand but the T is changed to U
what are the three steps of transcription?
initiation, elongation, termination and processing mRNA
how does transcription begin?
- RNA polymerase binds to a promoter sequence near the beginning of a gene either directly or through helper proteins
- once RNAP is bound to promoter DNA, the DNA strands unwind and the enzyme starts transcribing the template strand
what is the region of opened up DNA called?
transcription bubble
what mediates the binding of RNAP?
eukaryotes transcription factors
what happens during elongation?
- RNA polymerase moves along the DNA template and adds nucleotides in the 5’ to 3’ direction
- RNA polymerase reads the template DNA strand and adds nucleotides to the 3’ end of a growing chain
what happens during termination?
- transcription stops when RNAP reaches the DNA terminator
- RNA strand is released (RNA transcript)
- RNA polymerase dissociates from DNA
what happens during processing mRNA?
changing the premature mRNA into mature RNA
- splicing of mRNA
- alternative mRNA splicing
- post-transcriptional processing
what are introns?
non-coding sections of a gene ; do not code for a functional protein
- non-coding gene between coding sequence
what are exons?
portions of a gene that are expressed resulting in protein product
- real gene ; expressed/coding DNA
what happens during splicing of mRNA?
introns are removed and the exons are joined to form a mature mRNA molecule
- with the help of spliceosome
what happens during alternative mRNA splicing?
create many proteins from the same strand of DNA
- one single gene can result in different protein
versions
what happens during post-transcriptional processing?
both ends of an mRNA are modified by the addition of chemical groups
what are some of the chemical groups?
- add 5’ GTP cap to the first nucleotide which protects the transcription from being broken down and also assists in ribosome binding during translation
- add 3’ poly-A-tail at the back to increase stability and prevents degradation
- longer tail ; mRNA lasts longer ; make more proteins
