| what are nucleotide; nucleoside; nucleobase ? | Nucleotide =
– Nitrogeneous base – Pentose
– Phosphate
• Nucleoside =
– Nitrogeneous base – Pentose
• Nucleobase =
– Nitrogeneous base |
| what are Functions of Nucleotide ? | – Energy for metabolism (ATP)
– Enzyme cofactors (NAD+)
– Signal transduction (cAMP) |
| what's Chargaff's rules? | 1) the nucleotide composition of DNA varies among species. In other words, the same nucleotides do not repeat in the same order, as proposed by Levene.
2) almost all DNA--no matter what organism or tissue type it comes from--maintains certain properties, even as its composition varies. In particular, the amount of adenine (A) is usually similar to the amount of thymine (T), and the amount of guanine (G) usually approximates the amount of cytosine (C). In other words, the total amount of purines (A + G) and the total amount of pyrimidines (C + T) are usually nearly equal.
(This second major conclusion is now known as "Chargaff's rule.") |
| What are Palindromes and what structures they form? | Palindromic DNA (or RNA) sequences can form alternative structures with intrastrand base pairing.
they form :
-hairpin : which is when only a single DNA (or RNA) strand is involved.
-cruciform: when both strands of a duplex DNA are involved. |
| why the experiment of Avery, MacLeod, and McCarty significant? | Studies on the Chemical Nature of the Substance Inducing Transformation of Pneumococcal Types: Induction of Transformation by a Desoxyribonucleic Acid Fraction Isolated from Pneumococcus Type III.
which demonstrated that hereditary units, or genes, are composed of DNA,
and that DNA as the "transforming principle". |
| What type of chemical bonds determine the most of the stability of the helix in double-stranded B-form DNA? | The B form is the most stable structure for a random-sequence DNA molecule under physiological conditions its Antiparallel. Multitude of hydrogen and hydrophobic bonds between the polynucleotide strands provide stability |
| what are the dimensions of DNA double helix in angstroms? | 3.4 A between bases, 36A per turn, 20A wide. |
| how does ionic strength of a solution influence stability of DNA? | in low salt, a given DNA will melt at a lower temperature than in a higher salt concentration.
This is because DNA is a polyanionic molecule. The salt "shields" the negative charges on each phosphate.
-Melting temperature depends on C-G content |
| why it is advantageous for DNA to contain thymine, not uracil? | Deamination of cytosine (in DNA) to uracil occurs in about one of every 107 cytidine residues. its almost certainly the reason why DNA contains thymine rather than uracil. The product of cytosine deamination (uracil) is readily recognized as foreign in DNA and is removed by a repair system. |
| what's the role of DNA methylation in regulating gene expression, why DNA methylation is important? | it alters the expression of genes in cells as cells divide and differentiate from embryonic stem cells into specific tissues. changes are usually permanent and unidirectional, preventing differentiated cell from reverting to a stem cell or converting into another type of tissue. DNA methylation suppresses the expression of endogenous retroviral genes and other harmful stretches of DNA that have been incorporated into the genome of the host over time. |
| why DNA is more stable than RNA? | deoxyribose sugar, which contains one less oxygen-containing hydroxyl group, DNA is a more stable,RNA containing a ribose sugar, is more reactive than DNA and is not stable |
| how did how Meselson–Stahl experiment confirmed the hypothesis of Nikolai Koltsov? | he proposed that inherited traits would be inherited via a "giant hereditary molecule" made up of "two mirror strands that would replicate in a semi-conservative fashion using each strand as a template”,the replication mechanism that was implied by the double-helical structure through the Meselson–Stahl experiment. |
| what's the central dogma of molecular biology ? | the relationship between DNA, RNA, and proteins. DNA contains instructions for making a protein, which are copied by RNA. RNA then uses the instructions to make a protein. In short: DNA → RNA → Protein, or DNA to RNA to Protein. |
| what's Meselson–Stahl experiment ? | to long to explain here slide 36,37 |
