Cheatography
https://cheatography.com
Details aspects of gene expression and regulation
This is a draft cheat sheet. It is a work in progress and is not finished yet.
Genetic Material
-DNA primary source of heritable information (sometimes RNA)
-Info stored and passed through subsequent generations (mostly DNA sometimes RNA)
Base Pairing: A-T(U) and G-C
Purines: G and A; have a double ring structure
Pyrimidines: C, T, and U; have a single ring structure
Retroviruses: info flows from RNA to DNA, made possible by reverse transcriptase |
DNA Replication
DNA is synthesized in the 5’ to 3’ direction |
Semiconservative |
One strand of DNA serves as the template for a new strand of complementary DNA |
Helicase |
Unwinds the DNA strands |
Topoisomerase |
Relaxes supercoiling in front of the replication fork |
DNA polymerase |
Requires RNA primers to initiate DNA synthesis |
Leading Strand |
DNA polymerase synthesizes new strands of DNA continuously in 5'-3' direction |
Lagging Strand |
DNA polymerase synthesizes new strands of DNA DISCONTINUOUSLY (runs 3'-5') |
Ligase |
Joins the fragments on the lagging strand |
RNA Transcription
Initiation |
RNA polymerase binds to a sequence of DNA called the promoter. Once bound, RNA polymerase separates the DNA strands, providing the single-stranded template needed for transcription. |
Elongation |
RNA polymerase reads template strand and builds RNA molecule out of complementary nucleotides. RNA transcript carries the same information as the non-template (coding) strand of DNA, but it contains the base uracil (U) instead of thymine (T) |
Termination |
When termination sequence is transcribed, they cause the transcript to be released from the RNA polymerase |
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Eukaryotic Modifications
1. Addition of a poly-A tail.
2. Addition of a GTP cap.
3. Excision of introns and splicing and retention
of exons.
-Generates different versions of resulting mRNA molecule (alternative splicing)
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Prokaryotic Gene Regulation
Inducible |
Turned on by the presence of a particular small molecule (inducer) |
Repressible |
On by default but can be turned off by a small molecule (corepressor) |
Eukaryotic Gene Regulation
Chromatin accessibility |
More "relaxed" chromatin makes a gene more available for transcription |
Transcription |
Sets of transcription factor proteins bind to specific DNA sequences in or near a gene and promote or repress its transcription into an RNA |
RNA processing |
Splicing, capping, and addition of a poly-A tail, alternative splicing |
RNA stability/Translation |
Protein yield determines lifetime of RNA molecule in cytosol. Small regulatory RNAs called miRNAs bind to target mRNAs - chop them up |
Histones
Acetylation |
Makes DNA more accessible |
Methylation |
Makes DNA less accessible |
Mutations
Mutations are the main source of genetic variation
Biotechnology
Electrophoresis |
Separates molecules according to size and charge |
Polymerase chain reaction (PCR) |
Amplifies DNA fragments (makes more) |
Bacterial transformation |
Introduces DNA into bacterial cells (via plasmid) |
DNA sequencing |
Determines order of nucleotides in DNA molecule |
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