Central Dogma - answer✔✔DNA → RNA → Protein
Purines
- which bases?
- how many rings? - answer✔✔
Pyrimidines
- which bases?
- how many rings? - answer✔✔Remember: "Pyrimidine" has a "y" in it; so does "cytosine" and
"thymine."
Phosphodiester Bond - answer✔✔Joins one nucleotide to the next; between the 3rd C of one
ribose and the 5th C of the other to create the sugar-phosphate backbone
Directionality of DNA (convention) - answer✔✔5' → 3'
(but strands are antiparallel, so other strand is opposite)
3' of DNA attached to ... - answer✔✔OH
5' of DNA attached to ... - answer✔✔Phosphate group
DNA composition - answer✔✔1. Phosphate group
2. 5-Carbon sugar
3. Nitrogenous base (A, T, G, C)
Which nitrogenous bases form 2 hydrogen bonds? - answer✔✔A, T
Which nitrogenous bases form 3 hydrogen bonds? - answer✔✔G, C
Replisome - answer✔✔Proteins that govern the replication process
Origin of replication - answer✔✔Where replication begins. Prokaryotes have 1; eukaryotes have
many on each chromosome
DNA synthesis: direction of synthesis - answer✔✔5' → 3'
(the DNA is read 3' → 5')
Steps of replication (5) - answer✔✔1. Helicase unzips double helix
2. RNA polymerase builds a primer
3. DNA polymerase adds leading/lagging strands
4. Primers removed
5. Okazaki fragments joined
RNA vs. DNA: differences - answer✔✔RNA:
- C2 is oxygenated (has OH)
- Single stranded
- Uses uracil instead of thymine
- Can move through nuclear pores out of nucleus
DNA
- C2 is deoxygenaged (has H)
- Double stranded (double helix)
- Uses thymine
- Stuck in the nucleus
Transcription - answer✔✔Process of making RNA (rRNA, mRNA, tRNA)
Promoter - answer✔✔Required for transcription. Sequence of DNA nucleotides that signals
beginning point for transcription.
Primer - answer✔✔Required for DNA replication
Consensus sequence - answer✔✔Most common promoter sequences; closer the DNA
nucleotides are to the consensus sequence, the more tightly the RNA polymerase can bind, which
leads to more frequent transcription (and vice versa)
RNA polymerase - answer✔✔Synthesizes RNA in transcription
2. Elongation - Template/antisense DNA strand is read and complementary RNA synthesized in
5' → 3' direction (same as DNA synthesis); DNA is read in 3' → 5' (also same as DNA
synthesis)
3. Termination - temination sequence marks end, special proteins dissociate RNA pol from DNA
Gene regulation - answer✔✔Most occurs at transcription via repressors and activators, which
bind near promoter and affect activity of RNA polymerase
Operon - answer✔✔Entire transcript in a prokaryote; includes multiple genes (polycistrionic).
I.e., lac operon - operator, repressor, genes, promoter, etc.
RNA post-transcriptional processing - answer✔✔pre-mRNA altered in 3 ways:
1. addition of nucleotides
2. deletion of nucleotides
3. modification of nitrogenous bases
5' cap - answer✔✔Added to mRNA as an attachment site in protein synthesis and protection
against degradation by exonucleases. Done with GTP.
3' poly A tail - answer✔✔Added to mRNA to protect from exonucleases.
snRNPs - answer✔✔Recognize introns and snip them out
Intron - answer✔✔Non-coding region of mRNA. Is removed by snRNPs (and spliceosome
complexes) and then degraded in nucleus.
Exon - answer✔✔Coding region of mRNA. Remains after activity of snRNPs and spliceosome.
Then exits the nucleus for translation.
DNA denaturation: conditions, effects - answer✔✔Conditions:
1. Salt solution
2. High pH (basic) solution
3. High temperature
Effects:
- Double helix separates because hydrogen bonds are disrupted
- DNA with more G-C pairs (G-C forms 3 H bonds, while A-T has only 2) has a greater Tm, so
takes more energy to melt
Restriction Enzymes - answer✔✔- method bacteria use to protect themselves from viruses is to
cut viral DNA w/these (bacterial DNA is methylated, so differentiated)
- can form recombinant DNA (artificially) using these
Cloning DNA - answer✔✔Recombinant DNA can be placed in bacteria using a vector (plasmid
or virus), then grown. Screened by including an antibiotic resistance gene and a lacZ gene to find
which colonies actually took up the vector.
cDNA - answer✔✔Complementary DNA. Used often in cloning because has no introns (and
therefore is active). Produced in RT PCR from mRNA.
Southern Blot - answer✔✔Identifies specific sequences of DNA through nucleic acid
hybridization.
Northern Blot - answer✔✔Identifies specific sequences of RNA through nucleic acid
hybridization.
Western Blot - answer✔✔Detects protein levels with antibodies.
Genetic code: 3 major features - answer✔✔1. Degenerative: More than one codon for each
amino acid
2. Unambiguous: Each codon encodes for only ONE amino acid
3. Universality: nearly every living organism uses same code
Codon - answer✔✔Three consecutive nucleotides on mRNA
Stop codons - answer✔✔UAA, UAG, UGA
Start codon (and methoinine) - answer✔✔AUG
Convention for writing RNA - answer✔✔5' → 3'
Translation - answer✔✔Process of protein synthesis. Three steps: Initiation, elongation,
termination.
Translation (initiation) - answer✔✔mRNA has left nucleus via nuclear pores, and is now in
cytosol; initiation factors (proteins) help the 5' end of mRNA attach to the small ribosome
subunit. tRNA with 5'-CAU-3' anticodon gets methionine and goes into P site. This together is
called the "initiation complex."
Ribosome
- prokaryote
- eukaryote - answer✔✔In both prok and euk, made of rRNA and protein; small and large
subunits.
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