Chapter 2-Nucleic Acids Flashcards
Define purines
9-member double ring with 4N and 5C
- adenine and guanine
Define pyrimidines
6 member ring with 2N and 4C
- cytosine, thymine, uracil
How many nucleotides to make a complete turn of dna double helix?
10 nucleotids, 3.4nm (34 angstroms)
What is the diameter of DNA double helix?
1nm
Significance of DNA supercoiling (2)
- Compaction of DNA in nucleus
2. Easier strand separation for replication and transcription
List the types of coiled dna in increasing order in terms of distance travelled during agarose gel electrophoresis.
Nicked, linear, supercoiled, circular and ss
Describe the hairpin loop of RNA
2 regions of the same strand that are complementary in nucleotide sequence base pair to form a helix but ends in an unpaired stem/loop
Name 5 secondary structures of RNA
- Helix
- Hairpin Loop
- Bulge loop
- Interior loop
- Multi-branched loop
Describe what is a tRNA
- associated with 1 aa and carries a specific anticodon which will pair with codon sequence of mRNA in protein synthesis (translation)
- has an anticodon region that can base pair with the codon region on mRNA
- small chain of around 80 nucleotides
- 5 arms; 3 arms are hairpin loops, 1 arm is bulge loop
Describe micro RNA (miRNA)
- class of cellular RNAs that regulate protein expression at the translational level
- bind to complementary sequences of mRNA to inhibit translation (gene silencing)
Describe Long non-coding RNA (lncRna)
- > 200 nucleotides in length
- not translated into proteins
- found to alter mrna splicing and interact with splicing factors
- modify epigenetic state by recruiting chromatin remodelling proteins
- recruit/block transcription factors to affect gene expression
- often have little homology between species
Define splicing
Precursor mrna transcript is transformed into a mature mrna transcript where introns are excised and exons are splices together by spliceosomes
Benefits of studying nucleic acids
- New treatments and biomarkers for gene therapy, vaccines and personalised medicine
- New ways of manipulating cells by using siRNA and CRISPR
Difficulties in studying nucleic acids
Many methods require further development before they can reach the clinic
Describe alkylating agents (used in chemotherapy)
- induce covalent modifications of DNA, creating adducts not readily removed by the cell’s repair machinery
- cell either repairs or undergoes apoptosis—> results in cell cycle arrest and stops proliferation
- eg cisplatin
Describe anti-metabolites (used in chemotherapy)
- interfere with normal cell metabolism of nucleic acids or the enzymes that produce them
- some are purine/pyrimidine analogues that prevent biosynthesis or become incorporated into DNA
- eg methotrexate
Define biomarkers
A characteristic that is objectively measured and evaluated as an indicator of normal biologic processes, pathogenic processes or pharmacological responses to therapeutic intervention.
Describe short interfering RNA (siRNA)
- short SYNTHETIC RNA designed to specifically target an RNA for degradation
- same mechanism of action as miRNA (but r synthetic)
- can be introduces to cell via transfection, electroporation or chemical modifications
Define gene therapy
Experimental technique that uses genetic principles to treat disorders
Define gene therapy
Experimental technique that uses genetic principles to treat disorders
Advantages of mRNA vaccines
- Less time-consuming bc mRNA molecules are easier to produce than non-infectious viruses
At what wavelength does DNA and RNA most efficiently absorb UV light?
260nm
What concentration of DNA and RNA give 1 ABS?
In 1cm cuvette, 50ug/ml dsDNA or 40ug/ml ssRNA
Define the Tm of DNA
- temperature at which half of DNA are dsDNA and half are ssDNA
