Flashcards
Molecular biology
Cards in this deck (44)
- 1What are the requirements for performing the PCR reaction?Template DNA, deoxynucleotide triphosphates, a heat stable DNA polymerase (e.g. taq DNA polymerase) and primers
- 2What is the difference between northern and southern blotting?Northern blotting is used to fractionate RNA and southern blotting is used for DNA
- 3Give an example where you might use the northern blotting techniqueWhen analysing the expression of follicle stimulating hormone-β in different tissue types
- 4Why is PCR the preferred molecular diagnostic method of choice?It is cheaper, faster and more sensitive than southern blotting (although southern blotting is still used for diagnosing some disorders e.g. Fragile X syndrome)
- 5After 30 cycles of PCR, how many times will the target fragment be amplified?Approximately 2³⁰ fold
(as after n cycles of PCR there will be approximately 2^n copies of the fragment) - 6What 3 reactions are constantly repeated in the elongation cycle?Binding of aminoacyl-tRNA (needs GTP), the peptidyl transferase reaction and translocation (movement of the ribosome one codon along the mRNA-also needs GTP)
- 7What is the name of the initiating amino acid in prokaryote translation?N-formyl-methonine (instead of methonine in eukaryotes)
- 8How many ATP molecules are used for each amino acid incorporated into the protein?3x ATP
- 9How many molecules of GTP are used during the addition of one amino acid to the peptide chain?6 x GTP (one molecule for everytime an aminoacyl tRNA binds to the ribosome and one for everytime the ribosome moves one codon along the mRNA)
- 10In eukaryotes, what delivers aminoacyl tRNAs to the ribosome?EF-1a
- 11Name two groups of drugs active against prokaryotic ribosomes.Any two from;
Aminoglycosides, macrolides, tetracyclines and chloramphenicol - 12Name two drugs or toxins active against eukaryotic ribosomesRicin and diptheria toxin
- 13What are restriction enzymes?They are enzymes that recognise and cleave DNA at specific sequences. These are usually 4-6 base-pairs long
- 14What does palindromic mean in terms of restriction enzyme cutting sites?Both the top and the bottom strands have the same sequence
- 15Give an example of a restriction enzyme that cleaves to give blunt endsHae III
- 16Give an example of a restriction enzyme that cleaves DNA to give sticky endsEco RI
- 17What is the average size of a DNA fragment generated by Eco RI digestion?4,096 bp
- 18How many different fragments of DNA are generated if human DNA is digested with Eco RI?750,000 fragments (because the human genome contains 3x10⁹ base pairs of DNA and there is a recognition site for Eco RI every 4,096 bp therefore 3x10⁹ ÷4096 = 750,000)
- 19What material is used to make the gel for gel electrophoresis?Agarose or polyacrylamide
- 20In southern blotting, why do we treat the gel with sodium hydroxide?To denature the DNA- it breaks down the hydrogen bonds between the strands and allows us to "blot" DNA onto the nylon membrane
- 21Give an example of a genetic mutation that can be identified via southern blottingSickle cell disease- it is a recessive genetic disorder caused by a single mutation in the β-globin gene. Can detect the mutation via the restriction enzyme Mst II
- 22What base sequence is the initiator codon?AUG- codes for methionine
- 23Give two examples of stop codons.Any two from...
UGA, UAA and UAG - 24The genetic code is generally universal, however there are some minor variations. Give an example of where these may be seen.In some mycoplasma (primitive bacteria) or in the mitochondria
- 25How big are tRNAs?75-95 nucleotides long
- 26What is the effect of a nonsense mutation?A nonsense mutation will code for a stop codon therefore the production of that protein will be stopped prematurely normally leading to the production of an unfunctional protein
- 27What occurs to the DNA sequence in a frameshift mutation?There is a deletion of one or several nucleotides changing the way the codons are read. It may change all the codons downstream to the deletion
- 28Name two unusual bases tRNA's may contain?Any two from;
Thymine, dihydrouracil, pseudouracil and methylguanine - 29What sequence do all tRNA's have at their 3' end?CCA
- 30What is an aminoacyl tRNA?A tRNA that is attached to its amino acid
- 31What are the 5 arms of a tRNA molecule?They are the amino acid arm, the T arm, the D arm and the anticodon arm. (The variable arm may or may not be present)
- 32What are the enzymes called that link tRNA's to amino acids called?Aminoacyl-tRNA synthetases
- 33Once the pre-initiator complex has been formed, what activates RNAP II?TFIIE and TFIIH
- 34What phosphorylates RNAPII?TFIIH kinase
- 35What phosphorylates Ser-5?TFIIH, this triggers the release of RNAPII from the promoter
- 36What does chromatin packing determine?Whether or not DNA is accessible for transcription
- 37What are the two types of heterochromatin?Constitutive and facultative
- 38What type of chromatin is permanently silenced?Constitutive heterochromatin
- 39What is the function of TBP (TATA binding protein)?It binds at the TATA box and bends the DNA more than 80 degrees
- 40What do TATA-driven promoters contain?An initiator sequence (inr) and a TATA box
- 41What do TATA-driven promoters contain?An initiator sequence (inr) and a TATA box
- 42What do additional upstream control elements like the CAAT and GC box do to the promoter?They improve its efficiency
- 43What are the two subunits of TFIIDTBP (TATA binding protein) and TAF (TBP associated factors)
- 44What does the binding of TFIID to DNA initiate to form?The pre-initiation complex
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- Flashcards on Molecular biology, created by reynoldslaura on 30/04/2013.
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