A1.2.6 DNA as a double helix linked by hydrogen bonding between complementary base pairs Flashcards
How do G-C base pairs connect?
By 3 hydrogen bonds.
What forms the ‘rungs’ of the DNA ladder?
Pairs of nitrogenous bases held together by hydrogen bonds.
What do Chargaff’s Rules state about base pairing?
The amount of A equals T, and the amount of G equals C.
What is the directionality of the two DNA strands?
One strand runs 5’ → 3’ and the other runs 3’ → 5’.
What are the two distinct features created by the double helix structure?
Major groove and minor groove.
What is the minor groove in DNA?
Narrower and shallower, less accessible.
What do the terms 5’ and 3’ refer to?
The carbon atoms in the sugar molecule where the phosphate groups attach.
What is base stacking in DNA?
Hydrophobic interactions between adjacent base pairs that add to structural stability.
What are the key components of the DNA double helix?
Sugar-phosphate backbone and nitrogenous bases.
What are the four types of nitrogenous bases in DNA?
Adenine (A), Thymine (T), Guanine (G), and Cytosine (C).
If a DNA molecule contains 30% adenine, what percentage of thymine does it contain?
30% thymine.
Why are G-C pairs more stable than A-T pairs?
Because G-C pairs have an extra hydrogen bond.
How do A-T base pairs connect?
By 2 hydrogen bonds.
What factors contribute to the stability of the DNA double helix?
Hydrogen bonds and base stacking.
Why is the cumulative effect of many hydrogen bonds important?
While individual hydrogen bonds are weak, their cumulative effect makes the DNA structure very stable.
What role do hydrogen bonds play in DNA structure?
They provide specific base pairing and contribute to overall stability.
What is the major groove in DNA?
Wider and deeper, more accessible to proteins.
What is the sugar-phosphate backbone made of?
Alternating deoxyribose sugar and phosphate groups.
What is the structure of DNA described as?
A twisted ladder, where the sides are made of alternating sugar and phosphate molecules.
