Lecture 2 Flashcards
(31 cards)
What are nucleic acids made of?
Polymers made of nucleotides
What is the primary function of Deoxyribonucleic acid (DNA)?
Stores all the hereditary info within the cell and carries that from generation to generation
What percentage of DNA sequences are coding sequences?
1%
What are the building blocks of nucleic acids?
Nitrogen base, deoxyribose pentose sugar, glycosidic bond and phosphate group
What are the two types of nitrogenous bases in nucleic acids?
- Purines * Pyrimidines
According to Chargaff’s rule, what is true about purines and pyrimidines?
Total purines = total pyrimidines
Which bases pair together in DNA?
- G=C * A=T
What connects opposite bases within the DNA double helix?
Hydrogen bond
What is the structure of DNA?
Double-stranded helix
What is the significance of the 5’ and 3’ ends in DNA?
The first base is the 5’ end, the last base is the 3’ end
What is the role of DNA polymerase in DNA replication?
Catalyzes the addition of a deoxyribonucleotide to the 3ʹ end of a polynucleotide chain
What is the melting temperature (Tm) of DNA influenced by?
Nucleotide composition - those DNAs with a larger proportion of G–C base pairs exhibit a higher Tm
This is because three hydrogen bonds hold a G–C base pair together, compared with only two for the A–T base pair.
What is a replication fork?
Y-shaped structure where DNA replication occurs
What is the difference between the leading strand and the lagging strand in DNA replication?
Leading strand grows continuously; lagging strand is synthesized in chunks
What type of sugar is found in DNA?
Deoxyribose
What are in vitro studies?
Laboratory-based systems studying biological molecules outside their natural environment
What is necessary for DNA analysis regarding homogenization techniques?
Techniques depend on different organisms - large organisms require breakdown of tissue
What is the maximum absorbance wavelength for nucleic acids?
260 nm
What does the Beer-Lambert law relate to?
Absorbance and concentration of a solution
What is the equation for the Beer-Lambert law?
A = ε * c * l
A = Absorbance (no units)
𝜀
ε = Molar extinction coefficient (L·mol⁻¹·cm⁻¹)
𝑐
c = Concentration of DNA (mol/L)
𝑙
l = Path length of the cuvette (usually 1 cm)
What causes DNA to migrate in electrophoresis?
Negative charge from the phosphate sugar backbone
Smaller molecules move faster and farther through the gel pores.
What is the first step in preparing agarose gel for electrophoresis?
Dissolve 0.5-2% agarose in buffer
Lower % agarose (e.g., 0.7%) → larger pores → good for large DNA fragments
Higher % agarose (e.g., 2%) → smaller pores → good for small DNA fragments
What is added to the gel preparation to visualize DNA?
Ethidium bromide (EtBr)
What does a calibration ladder in gel electrophoresis indicate?
Presence of DNA in one line - it is a mixture of DNA, RNA, or protein fragments of known sizes. It serves as a reference standard to estimate the size of unknown biomolecules in a gel.
