Chargaff's Rule

Q.

If a double stranded DNA has 20% of cytosine, calculate the per cent of adenine in the DNA.

Q.

What is Chargaffs rule?

Q. In a DNA fragment, there are 8 turns with 40% of the bases are cytosine. What would be the total no. of hydrogen bonds present in this DNA fragments? 1. 184 2. 244 3. 192 4. 300

Q. The percentage of human genome which encodes proteins is approximately

1. 25%
2. Less than 2%
3. 5%
4. 99%

Q. In sea urchin DNA, which is double stranded, $17\%$ of the bases were shown to be cytosine. The percentages of the other three bases expected to be present in this DNA are:

1. G - 34 %, A - 24.5 %, T - 24.5 %
2. G - 17 %, A - 33 %, T - 33 %
3. G - 17 %, A - 16.5 %, T - 32.5 %
4. G - 8.5 %, A - 50 %, T - 24.5 %

Q. The following ratio is generally constant for a given species:

1. A+G/T+C
2. G+C/A+T
3. A+C/T+G
4. None of the above

Q.

The two strands of DNA are antiparallel and complementary.

1. True
2. False

Q. In DNA of certain organisms, guanine constitutes $20\%$ of the bases. What percentage of the bases would be adenine?

1. $10\%$
2. $30\%$
3. $40\%$
4. $20\%$

Q. In sea urchin DNA, which is double stranded, 17 % of the bases were shown to be cytosine (C). The percentages of the other three bases (G, A and T) expected to be present in this DNA are:

1. $G-8.5\%,A-50\%,T-24.5\%$
2. $G-34\%,A-24.5\%,T-24.5\%$
3. $G-17\%,A-16.5\%,T-32.5\%$
4. $G-17\%,A-33\%,T-33\%$

Q. What are purines?

Q. What does the image below represent?
5’--------GAATTC---------3’
3’--------CTTAAG---------5’
a) Replication
b) Deletion mutation
c) Start codon at 5’ end
d) Palindromic sequence
[1 mark]

Q.

If a double stranded DNA has 20% of cytosine, calculate the percent of adenine in the DNA?

Q.

In a 3.2 Kbp long piece of DNA, 820 adenine bases were found. What would be the number cytosine bases?

1. 1560

2. 1480

3. 780

4. 740

Q. If a double stranded DNA has 20 percent of cytosine, calculate the percent of adenine in the DNA.

Q. Which of the following is NOT true with regard to Chargaff’s rules?

1. A:T = 1:1
2. G:C =1:1
3. A+T : G+C = 1:1
4. A+G : T+C = 1:1

Q. Percentage of (G + C) is

1. $\frac{G+C}{A+T+G+C}\times 100$
2. $\frac{100}{A+T}\times G+C$
3. $\frac{G+C}{A+T+G+C}$
4. $\frac{(G+C)\times (A+T)}{100}$

Q. Elucidate the importance of Chargaffs rule in the structure of DNA molecules.

Q. Which is not correct according to Chargaff's rule?

1. $\frac{A+G}{T+C}=1$
2. $A+T=C+G$
3. $A+G=C+T$
4. Purines = Pyrimidines

Q. DNA has equal number of adenine and thymine residues $(A=T)$ and equal number of guanine and cytosine $(G=C)$. These relationships are known as

1. Coulomb's law
2. Le-Chatelier's principle
3. Van't Hoff plot
4. Chargaff's rule

Q. In DNA of certain organisms, guanine constitutes $20\%$ of the bases. What percentage of the bases would be adenine?

1. $10\%$
2. $20\%$
3. $30\%$
4. $40\%$

Q. If the total amount of adenine and thymine in a double-stranded DNA is 45%, the amount of guanine in this DNA will be

1. 22.5%
2. 27.5%
3. 45%
4. 55%

Q. If there is 20% adenine in DNA, the percentage of guanine will be

1. 20%
2. 10%
3. 40%
4. None of the above

Q.

In the DNA molecule

1. The total amount of purine nucleotides and pyrimidine nucleotides is not always equal.

2. Proportion of adenine in relation to thymine varies with the organism

3. There are two strands which run parallel in the 5'-3' direction.

4. There are two strands which run antiparallel - one in 5'-3' direction and other in 3'-5' direction

Q. If the total amount of adenine and thymine in a double- stranded DNA is 45%, what will be the amount of guanine in this DNA?

1. 27.5%
2. 22.5%
3. 45%
4. 55%

Q. Which of following is not correct according to Chargaff's rule?

1. $\frac{A}{T}=1$
2. $G+A=T+C$
3. $A+T=G+C$
4. $\frac{C}{G}=1$

Q. Tyrosine is a precursor of which of the following?

1. Melanin
2. Epinephrine
3. Norepinephrine
4. All of the above

Q. When $DNA$ was extracted from cells of $E.$ coli and analysed for composition of bases, it was found that $38\%$ of the bases were cytosine. What percentage of bases would be adenine?

1. $12$
2. $24$
3. $38$
4. $82$

Q. In a DNA percentage of thymine is 20% then what is the percentage of guanine : -

1. 20%
2. 40%
3. 30%
4. 60%

Q. What would be the percentage of thymine in a double stranded DNA sample, which contains 20% cytosine of the total bases?

1. 20%
2. 10%
3. 30%
4. 40%

Q. If a double stranded DNA has 20% of cytosine, what will be the percentage of adenine in it?

1. 20%
2. 30%
3. 40%
4. 60%