1.3 - Review of DNA and RNA Flashcards
1
Q
What is the composition of a nucleotide?
A
- Nitrogenous base
- A sugar
- One or more phosphates
2
Q
What is a nitrogenous base composed of and what is the bond?
A
- Purine or pyrimidine ring
- Base is linked to the 1’ carbon on a pentose sugar by a glycosidic bond from the N1 of the pyrimidines or the N9 of the purines
3
Q
What is the sugar of DNA?
A
- Has a 2’-deoxyribose
4
Q
What is the sugar of RNA and why is it different to that of DNA?
A
- Has ribose
- Difference is that RNA has hydroxyl group on 2’ carbon of the pentose
5
Q
What is a nucleotide?
A
- A nucleoside linked to a phosphate of a 5’ carbon
6
Q
What is a polynucleotide?
A
- Compound composed of several nucleotides
7
Q
What are the 4 nitrogenous bases of nucleic acids?
A
In DNA and RNA:
1. Adenine
2. Guanine
In DNA only:
3. Cytosine
4. Thymine
In RNA only:
5. Uracil
8
Q
What direction is nucleic acids written in?
A
5’ to 3’
9
Q
What is the structure of DNA?
A
- Forms a double helix consisting of two polynucleotide chains that are antiparallel
10
Q
How does DNA maintain a constant width?
A
- The double helix maintains a constant width because purines always face pyrimidines in the complementary A-T and G-C base pairs.
11
Q
What is the minor groove?
A
- Twisting of double strands around each other form a minor groove of 1.2nm (12 A)
12
Q
What is the major groove?
A
- 22A or 2.2 nm
13
Q
How much is one helical turn?
A
- 34A in length (3.4 nm) and is approx. 10.5 base pairs
14
Q
What is the double helix composed of?
A
- Sugar phosphate backbone (negative charge) and hydrogen bonds holding strand together
15
Q
What is the difference between B-DAN, A-DNA and Z-DNA?
A
- B-DNA is right-handed and turns clockwise
- A-DNA is the same as B-DNA but just shorter and thicker
- Z-DNA is longer and more narrow than B-DNA and is left-handed
