Download Cardiff International School Dhaka (CISD) Lost Class Make Up

Cardiff International School Dhaka (CISD)
Lost Class Make Up Assignment
Class: A3
Subject: Chemistry
Date: 1st (Sunday)-7th (Saturday) March 2015
Total Mark- 20
Instructions: All of your assignment must be done in A4 size paper. Mention your Name,
Class, Roll and Section clearly on the top sheet of your assignment.
Submission Deadline: Saturday 7th March 10.00 AM to the respective subject teacher. The
deadline is strict.
Name:.................................................................................................................................................
Class: .........................Roll: ........................ Sec: .................. Teacher: ......................................
Sunday-Saturday
1-7 March 2015
Lesson:
28.6 Nucleic Acids
Task:
Study –
i. The structure of DNA
ii. How DNA replicates
iii. The structure of RNA
Worksheet/Exercise:
Q1. The diagram below represents the basic chemical unit from which the nucleic acid DNA is
formed.
(a) State the name of:
[3]
(i) the whole chemical unit shown;
(ii) the component labelled X;
(iii) the component labelled Y.
(b) Name the four nitrogen-containing bases present in DNA.
[1]
Q2. (a) Representing the nitrogen-containing bases by B, sugars by S and the phosphate
groups by P, and using no other symbols, draw a diagram to show how these are linked in a
short length of double-stranded DNA.
Use full lines ( ________ ) for normal covalent bonds and dotted lines ( - - - - - - ) for hydrogen
bonds.
[2]
(b) Your sketch makes the two strands look identical. Ignoring the difference between the
bases explain:
(i) how the two strands differ;
[2]
(ii) give the technical term which describes this difference;
[1]
(iii) state how it is indicated on diagrams of DNA.
[1]
Q3.(a) An analysis of the bases in a sample of double-stranded DNA gave the partial result
below.
Adenine 23 mole %
Guanine 27 mole %
What would you expect the rest of the analysis to show? Explain your answer.
[1]
(b) What role do hydrogen bonds play in the accurate replication of DNA?
[1]
(c) DNA is replicated semi-conservatively. What is meant by the term in bold type?
[1]
Q4. (a) State three ways in which the structure of DNA differs from that of RNA.
[3]
(b) Describe the structure of tRNA.
[2]
(c) Describe the role of rRNA in protein synthesis.
[2]
Text Book/Reference Book:
Chemistry Coursebook, Page No. 421 - 424, Chapter – 28
Answer Keys:
Q1. Round shape denotes phosphate group and the other one is sugar unit.
Q2. (a) Opposite direction, Composition of nitrogen bases
(b) Complementary base pairs
(c) By using diagrams of different shapes
Q3. (a) adenine pairs with thymine and guanine pairs with cytosine
(b) Hydrogen bonding is a special type of bond. These hydrogen bonds are what allow for DNA
to have their unique structure. Hydrogen bonds occur between base pairs which link
complementary strands and enable replication.
(c) Semiconservative replication would produce two copies that each contained one of the
original strands and one new strand.
Q4. (a) For example: RNA contains the base uracil instead of thymine present in DNA.
(b) tRNA has got cloverleaf structure.
(c) Ribosomal RNA (rRNA) associates with a set of proteins to form ribosomes. These complex
structures, which physically move along an mRNA molecule, catalyze the assembly of amino
acids into protein chains. They also bind tRNAs and various accessory molecules necessary for
protein synthesis.
Help Lines:
For any assistance, please contact
Chemistry Teacher:
Jobaida Akther, [email protected]
Principal Head of School: G.M.Nizam Uddin, +88-01622181818, [email protected]