Question

15. Which one represents the correct DNA molecule based on the double helix model?

A. 5'-GAATTC-3'

     5'-GAATTC-3'

B. 5'-GAATTC-3'

     3'-GAATTC-5'

C. 5'-GAATTC-3'

     5'-CTTAAG-3'

D. 5'-GAATTC-3'

     3'-CTTAAG-5'

E. 5'-GAAUUC-3'

     3'-CUUAAG-5'

16. In the flow of genetic information (often called the Central Dogma), which of the following best represents the expression of genes?  

A. Protein—>RNA—>DNA 


B. DNA—>RNA—>Protein 


C. RNA—>DNA—>Protein 


D. DNA—>Protein—>RNA

E. RNA—>Protein—>DNA

17. Which of the following double-stranded nucleic acid represents the double helix model that is based on the two main concepts, antiparallel orientation and base-pairing rule, suggested by Watson and Crick?

A. 5'-AAGGCCT-3'

      5'-CCTTAAG-3'

B. 5'-AAGGCCT-3'

      3'-CCTTAAG-5'

C. 5'-AAGGCCT-3'

      5'-TTCCGGA-3'

D. 5'-AAGGCCT-3'

      3'-TTCCGGA-5'

E. 5'-AAGGCCT-3'

     3'-UUCCGGA-3'

Answer 1

Ans:-15) option d.

Double helix model of DNA was given by watson and crick in 1953.

This model was based on chargaff rule. Acc to this rule adenine always pairs with thymine and linked by 2 hydrogen bonds.

Guanine always pairs with cytosine with three hydrogen bonds.

According to this model:-

(i) dna is double stranded molecule with two strands having opposite polarity i. e both strands run antiparallely.

One strand goes from 5' to 3' while other strand goes from 3' to 5'.

ii) dna consists of 4 base pairs... Adenine, thymine, Guanine, cytosine.

Adenine pairs with thymine and Guanine pairs with cytosine.

iii) the two strands are coiled in right handed fashion.

I think it is enough for explaining the the question properly.

Now comes to question.

Option d is correct as here both strands are antiparellel and adenine is paired with thymine and guanine is paired with cytosine.

In option a, both strands are parallel and also pairing of base pairs is not correct. (guanine paired with guanine, thymine paired with thymine, adenine paired with adenine and cytosine paired with cytosine).

In option b, although both strands are antiparellel but pairing of base pairs don't occur accurately.

In option c, pairing of base pairs is accurate but both strands are parallel.

In option e, uracil is present instead of thymine. But in dna thymine is found. Uracil is found in rna.

Ans:-16) option b.

Central dogma is 2 step process where information flow from dna to proteins through rna. This by process of transcription and translation.

Dna - - - - - - >Rna - - - - - - >proteins

Dna is converted to rna through transcription and rna is converted to proteins through translation.

This occurs both in prokaryotes and eukaryotes.

Now comes to question, the sequence of central dogma is given correctly only in option b.

So option b is correct answer.

Ans:-17) option d.

This question is similar to question 15. So, i think there is no need to explain it again.

In option a, both strand are parallel and also pairing is not according to rule. So this option is incorrect.

In option b, although both strands are antiparallel but pairing is not accurate. So this option is incorrect.

In option c, although pairing is accurate but both strands are parallel. So this option is incorrect.

In option d, both strands are antiparallel and pairing is accurate. So this option is correct.

In option e, adenine is paired with uracil which is not possible in case of dna. So this option is incorrect.

Answer 2

1. the DNA molecules codes in the pallindromic sequence where two strand runs opposite to each other like 5'-3' to 3'-5' so the answer will be 1 because the above example is of E-coli which is extensively used in genetic research. last option is incorrect because it contain Uracil which is absent in DNA

2. Central Dogma follows a sequence DNA-RNA-Protein.

3. D is correct because it follows pallindromic and Antiparallel sequence where Adenine pairs with thymine and cytosine pairs with guanine.in 5'-3' to 3'-5' manner