Dna Double Helix
High-Yield Trend
Questions 10 MCQs
One turn of the helix in a B-form DNA is approximately:
| 1. | 20 nm | 2. | 0.34 nm |
| 3. | 3.4 nm | 4. | 2 nm |
Antiparallel strands of a DNA molecule mean that:
| 1. | one strand turns anti-clockwise |
| 2. | the phosphate groups of two DNA strands, at their ends, share the same position |
| 3. | the phosphate groups at the start of two DNA strands are in opposite positions (pole) |
| 4. | one strand turns clockwise |
The length of the DNA molecule greatly exceeds the dimensions of the nucleus in eukaryotic cells. How is this DNA accommodated?
1. Deletion of non-essential genes
2. Super-coiling in nucleosomes
3. DNAse digestion
4. Through the elimination of repetitive DNA
The two polynucleotide chains in DNA are:
1. parallel
2. discontinuous
3. antiparallel
4. semiconservative
| 1. | The total amount of purine nucleotides and pyrimidine nucleotides is not always equal |
| 2. | There are two strands, which run parallel in the 5' → 3’ direction |
| 3. | The proportion of adenine in relation to thymine varies with the organism |
| 4. | There are two strands, which run antiparallel - one in 5' → 3’ direction and the other in 3’→ 5’ |
The diagram shows an important concept in the genetic implication of DNA. Fill in the blanks A to C.
| 1. | A - translation B - transcription C - Erwin Chargaff |
| 2. | A -transcription B - translation C - Francis Crick |
| 3. | A - translation B - extension C - Rosalind Franklin |
| 4. | A - transcription B - replication C - James Watson |
Which one of the following is not applicable to RNA?
1. Complementary base pairing
2. 5' phosphoryl and 3' hydroxyl ends
3. Heterocyclic nitrogenous bases
4. Chargaff's rule
In the polynucleotide chain of DNA, a nitrogenous base is linked to the –OH of:
| 1. | 2'C pentose sugar | 2. | 3'C pentose sugar |
| 3. | 5'C pentose sugar | 4. | 1'C pentose sugar |
If Adenine makes 30% of the DNA molecule, what will be the percentage of Thymine, Guanine and Cytosine in it?
| 1. | T:30 ; G:20 ; C:20 | 2. | T:20 ; G:25 ; C:25 |
| 3. | T:20 ; G:30 ; C:20 | 4. | T:20 ; G:20 ; C:30 |
| (a) | Euchromatin is loosely packed chromatin. |
| (b) | Heterochromatin is transcriptionally active. |
| (c) | Histone octomer is wrapped by negatively charged DNA in nucleosome. |
| (d) | Histones are rich in lysine and arginine. |
| (e) | A typical nucleosome contains 400 bp of DNA helix. |
| 1. | (a), (c), (e) only | 2. | (b), (d), (e) only |
| 3. | (a), (c), (d) only | 4. | (b), (e) only |