Genetics Flashcards
DNA is a polymer consisting of deoxyribonucleoside monophosphates covalently linked by _____ bonds
3’ 5’ phosphodiester bonds
2 antiparallel strands of DNA are joined By ____ bonds
Hydrogen
Highly repetitive sequences (TG-rich) at the end of the chromosomes
Telomeres
Percent if cellular DNA located in mitochondria
1%
Structural form of DNA
Right handed helix
11 base per turn
Moderately dehydrated B form
A DNA
Structural form of DNA
Right handed helix
10 residues per turn
B DNA
Structural form of DNA
Left handed
Z DNA
Structural form of DNA
12 base pairs per turn
Z DNA
Structural form of DNA
Found in areas of alternating purines and pyrimidines
Z DNA
Polymer consisting of purine and pyrimidine ribonucleotides linked by 3’ 5 phosphodiester bonds
RNA
Sugar moiety of DNA
Deoxyribose
DNA OR RNA
Double stranded
DNA
DNA OR RNA
SINGLE stand
RNA
DNA OR RNA
Chargaffs rule does NOT apply
RNA
DNA OR RNA
Stabel
DNA
DNA OR RNA unstable
RNA
DNA OR RNA
Cannot be hydrolyzed by alkali due to the absence of 2 OH group
DNA
DNA OR RNA
Cam be hydrolyzed by alkali due to 2’3’ cyclic diesters of the mononucleotides
RNA
Copies genetic info from DNA
serves as template for protein synthesis
mRNA
mRNA structure in eukaryotes
Methylguanosine cap at 5’ 3end
Poly(A) tail at the 3’ end
Contributes to formation of ribosomes which act as the site for protein synthesis
rRNA
Adapter molecule that translates the nucleotide sequence if mRNA into specific AA
TRNA
Contains anticodons
TRNA
Cloverleaf appearance in 2D
Trna
Acceptor arm of TRNA terminates at what nucleotide
tRNA
Involved in rRNA and mRNA processing and gene regulation (eg removal of introns)
Small nuclear RNA
Micro RNA
Silencing RNA
Noncoding regulatiry RNA
DNA replication occurs in what phase of cell cycle
S phase
Each strand becomes part of daughter strand
Ech stand serves as template for complementary daughter strand
Semi conservative process
Steps in DNA replication
Origin of replication is recognized by ___
ORC origin recognition complex
DNAa protein in E coli
Steps in DNA replication
Unwinds double helix in a process driven by ATP
Helicase
Steps in DNA replication
Maintains separatikn of parent strands
Single stranded DNA binding proteins
Relieves torsio al strain that result from helicase-induced unwinding
Topoisomerase
Swivelase
Topoisomerase type I
Gyrase
Type II topoisomerase
Topoisomerase inh by fluoroquinolones
Type II (Gyrase)
Synthesizes short segments of complementary RNA primers
Primase
Steps in DNA replication
Elongates DNA strand by adding new deoxyribonucleotides
DNA polymerase III
Direction of synthesis
5’ to 3’
Strand that is synthesized continuously
Leading stand
Strand that consists of okazaki fragments
Lagging
Direction for proof reading by exonucleases
5’ to 3’
Fills tha gap with deoxyribonucleotides
DNA pol I
Seals the nick by catalizing the formation of the last phosphodiester bond
Requiring hydrolysis of ATP
DNA ligase
DNA polymerase
Gap filling following DNA replication
Repair and recombination
I
DNA polymerase
Proof reading and repair
E coli
II
DNA polymerase
DNA repair
Eukaryotes
Beta
DNA polymerase
Mitochondrial synthesis
Eukaryotes
Gamma
DNA polymerase
Processive, leading strand synthesis
III or epsilon
Primase
DNAG or alpha
Processive
Lagging stand synthesis
DNA polymerase
Delta
DNA lesion
Errors that escaped proof reading
Mismatched strand
DNA lesion
Exposure to UV light
Pyrimidine dimers
Usually thymine
DNA lesion
Spontaneous or deaminating compounds
Base alterations
Eg cytosine to uracil or guanine to xanthine
DNA lesion
Ionizing radiation
Free radicals
Anti-tumor drugs
Double strand breaks
DNA lesion
HNPCC (Lynch syndrome)
Mismatched strand
DNA lesion
Xeroderma pigmentosum
Pyrimidine dimers
DNA lesion
MUTYH-associated polyposis
Base alterations
DNA lesion
SCID
Breast CA susceptibility 1 and 2
Double strand breaks
Repair mechanism
Mismatched strand
Mismatch repair
DNA lesion
Pyrimidine dimers
Nucleotide excision repair
DNA lesion
Base alteration
Base excision repair
DNA lesion
Double stand breaks
Homologous recombination
Synthesis of RNA usinf DNA as template
Transcription
Enzyme for transcription
DNA-dependent RNA polymerase
rRNA
Pol I
tRNA, 5S rRNA
III
mRNA, lncRNA, miRNA, SnRNA
II
RNA binds to DNA promoter sequence
Initiation
Prmoter squence in prokaryotes
-35 sequence TTGACA Pribnow box (TATAAT), about -10 bp
Promoter sequence in eukaryotes
TATA or Hogness box, about -25 bp
CAAT box, about -70 to 80 bp
Occurs to create a transcriptionbubble in eukaryote initiation of transcriptiom
Unwinding of DNA
Local unwinding of the DNA continues in what direction
5’ to 3’
Step in transciption
RNA ploymerase synthesizes RNA using nucleoside monophosphates releasing pyrophosphate each time
Elongation
Termination signal that requires formation if hairpin loop
p-independent
Termination signal that requires p-protein to release RNA from DNA
P-dependent
Post transcriptional modifications
___ are removed
____ are spliced together
Introns
Extrons
Post transcriptional modifications (4)
Additin of 7-methylgunaosine cap
Addition of poly(A) tail
Addition of -CCA tail
Methylation
Reduction
Deamination
And rearrangements of glycosidic bonds to create unual bases
Encodes Beta galactosidase
Z gene
Encodes galactosidase permease, a transport protein required for entry of lactise into the cell
Y gene
Encodes thiogalactoside transacetylase, whose function is unknown
A gene
Encodes thiogalactoside transacetylase, whose functions is unkown
A gene
Encodes a lac repressor protein that is constitutively expressed and located at a distant site in DNA
i Gene
Template for translation aka protein synthesis
mRNA
Adapter molecule in translation
tRNA
Total codons
64
Total codons that code for AA
61
Stop codons
UAG
UAA
UGA
Start of initiating codon for methionine in eukaryotes or formylmethionine in prokaryotes
AUG
Characteristics of the genetic code
Multiple codons may code for the same AA
Degenerate
Characteristics of the genetic code
A specific codon always codes for the same AA
Unambiguous
Characteristics of the genetic code
The codons are read in a continuing sequence of nucleotide triplets until a translation stop codon is reached
Nonovelapping
Characteristics of the genetic code
It has beed conserved from very early stages of evolution with only slight difference in the manner in which the code translated
Universal
Contains the first codon for translation
tRNA
Before initiation, aminoacyl-tRNA synthetases attach AA to their respective tRNAs
Charging
Translation
Site of incoming aminoacyl tRNA
A site
Translation initiation
Occupied by peptidyl-tRNA
P site
Translation initiation
Occupied by the empty tRNA
E site
A cyclic proces on the ribosome in which one AA at a time is added to the growing peptide chain
Elongation
Translation
Elongation Steps
Aminoacyl tRNA binds to _____ site except in the first aminoacyl-tRNA which binds to ____site
A site
P site
Peptide bond formation is catalyzed by
Peptidyltransferase
Translation
Elongation Steps
Translocation of the ribosome on the ____
mRNA
Translation
Elongation Steps
Expulsion of the deacylated tRNA from
P and E site
Step in translation
Occurs when one of the three termination codons moved into the A site
Termination
Step in translation
Results in the release of the newly synthesized protein and dissociation of the ribosomes and mRNA
Termination
Addition of single AA to the polypeptide chain requires cleavage of four high energy bonds from ____ and ____
ATP and GTP
tRNA aminoacylation (ATP)
Loading of tRNA onto ribosome (GTP)
Translocation (GTP)
Post-translational modifications
Removal of excess AA
Phosphorylatiom
Glycosylation
Hydroxylation
Marks defective proteins for destructiom
Ubiquitin
Degrades defective proteins
Proteasomes
Peptide toxid alpha aminitin inhibits ______
RNA POL II
Diphtheria toxin inhibits ——- preventing translocation
Results in local tissue translocation and pseudomembrane formation
Elongation Factor 2
2 Inhibitors of transcription
Rifampicin
Dactinomycin
Inhibitors of transcription
Binds to beta subunit of bacterial DNA-dependent RNA polymerase
Rifampicin
Inhibitors of transcription
Binds to the DNA template and interferes with the movement of RNA polymerase during transcription
Dactinomycin
Protein synthesis inh
Binds to 30s subunit and interferes with initiation
Streptomycin
Aminoglycosides
Protein synthesis inh
Prevents binding of aminoacyl tRNA to the A site
Tetracycline
Protein synthesis inh
Inhibits prokaryotic peptidyltransferase
Chloramphenicol
Protein synthesis inh
Bind to the 50s subunit and inhibits translocation
Clindamycin and macrolides
Types of point mutations
Transition
Transversion
Purine to purine
Pyr to pyr
Transition
Pur to pyr or
Pyr to pur
Transversion
New codon codes for same AA
No effect on protein
Silent mutation
New codon codes for diff AA
Variable effects on protein
Missense
New codon is stop codon
Nonsense mutation
Deletion or addition of bases that should not bemmultiples 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
Tay Sachs
Gaucher
B thalassemia
Splice donor or acceptor
Variable effects ranging from addition or deletion of a new AA to deletion of entire exon
Splice donor or acceptor
Huntingtong dse
Fragile X syndrome
Myotonic dystrophy
Triple repeat expansion
Diseases show anticipation in pedigree
Expansions in coding regiond cause protein product to be longer than normal and unstable
Triple repeat expansion