Transcription Flashcards
What is RNA?
• RNA (ribonucleic Acid): o 4 bases: Adenine, Guanine, cytosine & Uracil. o Uracil = pyrimidine o Ribose (5C) + phosphate o Single stranded.
What are the Differences:DNA vs RNA?
o Ribose not deoxyribose o Uracil not thymine o RNA is easily altered o RNA is single stranded o RNA is shorter o RNA doesn’t usually form a stable secondary structure.
What are the types of RNA?
- m/t/r.
Describe Messenger RNA (mRNA).
o Variable sizes
o Observed synthesis of certain enzymes is rapidly turned on and off = mRNA must be rapidly made and short lived.
o RNA is complementary to its DNA template.
What is a gene?
- Genes are small sections of the DNA genome which can code for a particular protein/RNA.
Describe Transcription: describe the steps and regions of DNA/ proteins involved at each step .
LONG.
What parts of DNA are transcribed?
o Not all DNA is transcribed into RNA but transcribed in small units containing 1+ genes.
What is an area of DNA called if it transcripts one gene? Multiple?
o Monocistronic transcripts just 1 gene – polycistronic transcripts for 1+ genes.
Describe initiation.
1 .Initiation:
• Promoter regions (start signal) - recognised by RNA polymerase shows where to initiate transcription upstream from start codon.
• Promoter may also bind with other proteins (transcription factors) – control levels of gene transcription.
• Once RNA polymerase binds to promoter transcription initiates.
• NO PRIMER REQUIRED.
Describe elongation.
• The carrying on of RNA polymerase reading the DNA template to produce more of the RNA strand.
Describe termination.
- At transcriptional terminator (stop signal) ne RNA is released.
- RNA polymerase dissociates from the DNA.
Describe RNA Polymerase. What does it need? What can it do?
o RNA produced from DNA dependant RNA polymerase.
o RNAP relies of DNA template & nucleoside triphosphate precursors (no primer needed).
o Can bind and unwind DNA.
o Ability to know where to stop and start transcription.
Describe RNA processing and Exons & Introns. What is added to each end? What removes non-coding sections?
o Exons are the coding sequences and are split by introns- non-coding sequences. Introns=n Exons=n+1
o RNAP transcribes both exons and introns (cannot tell the difference).
o A modified G-CAP is added to the 5’ end.
o Introns are then spliced out by a spliceosome.
o A polyA tail is then added to the 3’ end.
o The mature RNA is the transported to the cytoplasm for translation.
What are prok/euk difference?
o Prokaryotes can have polycistronic mRNA = codes for 2+ proteins.
o Eukaryotes only have monocistronic mRNA = codes for 1 protein.
What is the role of Transcription in disease:.
o Transcription factors and promotors play a major part in health and disease.
What is a tumour suppressor?
o P53= tumour suppressor (guards cancer)- mutation in this gene reason for 50% of cancers. Majority of other 50% from mutations affecting p53 function.
What treats breast cancer?
- Tamoxifen – inhibits oestrogen by binging to its receptor- therefore turns off production of oestrogen.
What disease is due to mutations in a transcription factor that leads to inappropriate transcription of several genes?
- Rett syndrome: neurodevelopmental disorder affecting 1/15000 female births- detected after 1st birthday – loss of speech and motor skills.
o Due to mutations in transcription factor that would normally reduce transcription leads to inappropriate transcription of several genes- caused by mutation in male spermatogenesis.
What is the difference between humans and other mammals in Transcription and evolution:.
o Differences between humans and other mammals, is due to the same set of genes being regulated. o Most differences are due to changes in promoter sequences.
What gene is involved in learning, memory &experience of pain & social bonding? What animal is it higher in?
- Dynorphin
o Dynorphin is higher in humans due to differences in the promoter region.
What makes Bat forelimbs are longer?
- partly due to increased expression of transcription factor Prx1. (can be inserted into mouse).
