GENETICS Flashcards
DNA TO RNA
Transcription
RNA to DNA
Reverse Transcription
RNA to Proteins
Translation
Histones have a high content of what AA.
arginine and lysine
The process of disrupting the double helix is called
denaturation
Thymine = Adenine has how many Hydrgen bonds?
2
Cytosine = Guanine has how many hydrogen bonds
3 (stronger)
*Note that there are three hydrogen bonds between GC and just two
hydrogen bonds between AT. Thus, DNA strands with a greater
proportion of GC nucleotide pairs will be more difficult to separate.
Copies genetic information from DNA and serves as the template for protein synthesis
MESSENGER RNA (mRNA)
Prokaryotes have _______ subunits, made up of 3 types of rRNA: 16S, 23S, and 5S
50S and 30S
Differentiate DNA and RNA
MESSENGER RNA (mRNA) structure
- In eukaryotes
- Methylguanosine cap at the 5’-end
- Poly(A) tail at the 3’-end
- The primary transcript undergoes splicing prior to protein synthesis
Contribute to the formation and function of ribosomes, which act as the site for protein synthesis
RIBOSOMAL RNA (rRNA)
Eukaryotes have ______ subunitis, made up of four types of cytosolic rRNA: 18S, 28S, 5S, 5.8 S
60S and 40S
Adapter molecules that translate the nucleotide sequence of mRNA into specific amino acids
TRANSFER RNA (tRNA)
DNA REPLICATION occurs during what phase of the cell cycle?
S phase
The origin of replication (ori) is recognized by a group of proteins called ____
origin recognition complex (ORC)
___unwinds the double helix, in a process that is driven by ATP
Helicase
maintain the separation of the parent strands
Single-stranded DNA-binding proteins
relieve torsional strain that results from helicase-induced unwinding
Topoisomerases
o Type I (Swivelase)
o Type II (Gyrase), inhibited by fluoroquinolones
synthesizes short segments of complementary RNA primers
Primase
elongates the DNA strand by adding new deoxyribonucleotides
DNA polymerase III
- Synthesis proceeds in the 5’ to 3’ direction only
- Leading strand is synthesized continuously
- Lagging strand consists of Okazaki fragments
- Mismatched nucleotides are removed using the enzyme’s 3’→5’ exonuclease (proofreading)
When another primer is reached, _____ removes the ribonucleotides using its 5’→3’ exonuclease
DNA polymerase I
*fills the gap with deoxyribonucleotides
seals the nick by catalyzing the formation of the last phosphodiester (joins 2 nucleotides) bond, requiring hydrolysis of ATP
DNA ligase
DNA Lesion: Mismatched Strand
DNA lesion: Pyrimidine dimers (Usually thymine)
DNA Lesion: Base alterations (e.g., cytosine to uracil, or guanine to xanthine)
DNA Lesion: DOuble strand breaks
inhibits topoisomerase
Etoposide
Enzyme for Transcription (DNA to RNA)
Enzyme: DNA-dependent RNA polymerase
- No primer needed, no proofreading activity
- In eukaryotes, the polymerases synthesize specific RNA molecules:
o ______are DNA sequences that stimulate transcription rate
o _______ inhibit transcription
Enhancers
Silencers
What are the 3 stop codons that terminate translation
(UAG, UAA, UGA)
Start or initiating codon in eukaryotes
(AUG) methionine
Start or initiating codon in prokaryotes
formylmethionine
- The poisonous mushroom Amanita phalloides (“death cap”) contains the peptide toxin α-amanitin which inbitits the RNA polymerase II
- Presents with gastrointestinal symptoms, acute liver failurea, and may be fatal
AMANITA MUSHROOM POISONING
o Inactivates the eukaryotic elongation factor EF-2, preventing translocation
Exotoxin of Corynebacterium diphtheriae
• Binds to the β subunit of bacterial DNAdependent RNA polymerase
Rifampicin
Binds to the DNA template and interferes with the movement of RNA polymerase during transcription
Dactinomycin
Bind to the 30S subunit and interferes with initiation
aminoglycosides and streptomycin
Prevents binding of aminoacyl-tRNA to the A site
Tetracycline
Inhibits peptidyltransferase prokaryotic
Chloramphenicol
Inhibits eukaryotic peptidyltransferase
Cycloheximide
purine to purine or pyrimidine to pyrimidine
Transition
purine to pyrimidine or pyrimidine to purine
Transversion
- New codon codes for same amino acid
- No effect on protein
Silent Mutation
- New codon codes for different amino acid (conservative if new amino acid is similar in chemical structure)
- Variable effects on protein
Missense Mutation
- New codon is a stop codon
- Shorter than normal, usually non-functional protein
Nonsense Mutation
- Deletion or addition of bases that should not be multiples of three
- Shorter than normal, usually non-functional protein
FRAME SHIFT MUTATION
- Loss of large areas of chromosomes during unequal crossover in meiosis
- Loss of function
- Protein shorter than normal or entirely missing
LARGE SEGMENT DELETION
- Splice site is lost
- Variable effects ranging from addition or deletion of a few amino acids to deletion of an entire exon
- Examples: Tay-Sachs, Gaucher, β-thalassemia
SPLICE DONOR OR ACCEPTOR
- Expansions in coding regions cause protein product to be longer than normal and unstable
- Diseases often show anticipation in pedigree
TRIPLE REPEAT EXPANSION
CAG repeats
Huntington Disease
CGG repeats
Fragile X Syndrome
CTG repeats
Myotonic Dystrophy
