Lecture 12 Flashcards
(59 cards)
The central dogma refers to:
which is ___directional
the flow of information in the cell
unidirectional
Define a gene
a gene is a region of DNA that directs the synthesis of an RNA molecule
- it’s a unit of heredity
What’s a promoter?
a DNA sequence that directs/ regulates transcription
- site of RNA polymerase assembly
the first nucleotide to be transcribed is at ____[number] on the ____
(start site of transcription- where there’s a start codon)
+1
double stranded DNA
A common promoter in prokaryotes is the _______
- the ___ sequence is A/T rich. Why?
- the ___ sequence orients ___ ____
- the minus 10 and minus 35 combo
- minus 10. Because A and T is a weaker base pair (so it’s easier to pull apart the DNA)
- minus 35. orients RNA polymerase
What are the -10 and -35 sequences?
specific 6 base pair sequences common to most bacterial promoters
(the -10 and -35 combo)
mRNA is synthesized in what direction?
5’ to 3’
Directions:
Transcription occurs __ to ___ by reading the template strand __ to ___
5’ to 3’
template is read 3’ to 5’
True/ false
There are multiple genes on each chromosome
True
What is transcription?
the process of copying a segment of DNA into RNA
Describe the template strand
the strand of DNA that’s used in transcription
- runs 3’ to 5’ away from the promoter
Describe the coding strand
complementary and antiparallel to the template strand
- runs 5’ to 3’ away from the promoter
- NOT used in transcription
Define “transcript”
a piece of RNA that’s the product of transcription
How does RNA pol “know” where a gene is?
it’s recruited to a promoter by transcription factors
compare DNA polymerase and RNA pol.
list 3 differences
DNA:
- takes part in DNA replication
- requires a primer
- useful for both strands of DNA
RNA:
- takes part in transcription
- does not require a primer
- acts only on the template strand of DNA
Transcription vs. translation?
Transcription is DNA –> RNA
Translation is RNA –> protein
*transcription comes first
define genetic code
Genetic code is the term we use for the way that the four bases of DNA–the A, C, G, and Ts–are strung together in a way that the cellular machinery, the ribosome, can read them and turn them into a protein. In the genetic code, each three nucleotides in a row count as a triplet and code for a single amino acid.
which experiment helped determine the universal genetic code?
Nirenberg experiment
what are the 3 post-transcriptional modifications? Where do they occur?
- Addition of a methyl-guanosine cap at the 5’ end
- addition of 100-200 adenosines to the 3’ end, known as the poly-A tail
- Splicing
They occur in the nucleus of eukaryotes
what’s the function of the first 2 post-transcriptional modifications?
(meG cap and poly-A tail)
they both function to increase stability of mRNA in cytoplasm
- they prevent/ delay exonuclease digestion (of our own mRNA!)
what’s an exonuclease?
evolved from an antiviral response- degrades any foreign RNA (like covid!)
- our own RNA is protected from exonuclease digestion by the post-transcriptional modifications: meG cap and poly-A tail
- eukaryotes only
Fill in the blank (RNA Polymerase)
- RNA pol is part of a transcription initiation complex that assembles at the _____
- RNA pol synthesizes RNA ___’ to __’ (by reading DNA __’ to __’)
- RNA pol “knows” where a gene is because it’s recruited to a promoter by ____ _____
- RNA pol ____(does/ does not) require a primer and has its own “____” activity.
- promoter
- RNA: 5’ to 3’ by reading DNA 3’ to 5’
- transcription factors
- does not
helicase activity (can open DNA on its own)
template strand is chosen based on the direction of the ____
promoter
if it’s on the right, the bottom strand is the template
As mRNA is elongated, the area that’s unwound is called the ____ ____
transcription bubble
