WORKSHEET 1
CLASS:- 12
1.
BIOLOGY
Name the enzyme involved in the continuous replication of DNA Strand. Mention the polarity of the template strand?
-(1)
Ans. DNA polymerase is involved in continuous replication of DNA strand------- 1/2.
The polarity of template strand is 3’
2.
3.
4.
5.
MAX :-10 MARKS
5’------1/2
Are flippers of penguin and dolphin homologous or analogous? What type of evolution has brought such a similarity
in them?
-(1)
Ans .They are analogous. ---1/2
Convergent evolution brought similarity in them ---1/2
Mention the role of codons and AUG and UGA during protein synthesis?
-(1)
Ans. The codon AUG initiate protein synthesis----1/2
Whereas the codon UGA stops protein synthesis----1/2
How do you consider tendrils of cucurbita and thorns of Bougainvillea as
-(2)
Homologous structure?
Ans. Both of them are stem modification and thus are structurally similar but both have different functions-----1
Thus they are homologous----1
Answer the following questions based on meselson and Stahl’s experiment:
-(2)
(a) Write the name of the chemical substance used as a source of nitrogen in the
Experiment by them.
(b) Why did the scientist synthesize the light and the heavy DNA molecules in the organisms in the experiment?
(c) How did the scientist make it possible to distinguish the heavy DNA molecules from the light DNA molecule?
Explain?
(d) Write the conclusion the scientist arrive at after completing the experiment.
Ans.
6.
(a) Ammonium chloride (NH4Cl)----1/2
(b) To check if DNA replication was semi-conservative----1/2
(c) The heavy and light DNA molecules were distinguish by the centrifugation in a cesium chloride density gradient---1/2
(d) The scientist concluded that DNA replicates semi-conservatively----1/2
The base sequence in one of the strand of DNA is TAGCATGAT.
(3)
(a)Give the base sequence of its complementary strand?
(b) How are these base pairs held together in a DNA molecule?
(c)Explain the base complementarity rules. Name the scientist who framed this rule.
Ans.
(a) The complementary strand is ATCGTACTA ----1
(b) The base pairs are held together by hydrogen bonds in a DNA molecule. A and T are held by two hydrogen bonds
while G and C are held by three hydrogen bonds-----1
(c) Watson and Crick frame the base complementarity rule. The rule states that the ratios between Adenine and
Thymine , and Guanine and Cytosine are constant and equal one---1