D B 0 1 4 | C H A P 5

1 | P a g e

CHAPTER 5: EXPRESSION OF BIOLOGICAL INFORMATION

Subtopic 5.1 DNA and genetic information

Learning

Outcomes

a) State the concept of Central Dogma.

Definition of Central Dogma:_________________________________________________________

__________________________________________________________

State the concept of Central Dogma: State the process involve.

Subtopic 5.2 DNA replication

Learning

Outcomes

a) Describe semi-conservative replication of DNA.

b) State the enzymes and proteins involved in DNA replication.

c) Describe the mechanism of DNA replication and the enzyme

involved.

Semi-conservative model replication of DNA

BIOLOGY WORKSHEET

D B 0 1 4 | C H A P 5

2 | P a g e

Semi-conservative replication:

_______________________________________

_______________________________________

_______________________________________

_______________________________________

Enzymes and proteins involved in DNA replication:

No. Enzyme/Protein Function

1 Helicases

2 Topoisomerase

3 Primase Catalysed the synthesis of short RNA primer (using DNA strand as a

template), generally 5-10 nucleotides long.

4 DNA polymerase I

5 DNA polymerase III

D B 0 1 4 | C H A P 5

3 | P a g e

6 Cataysed the joining of Okazaki fragments of lagging strand; on

leading strand, catalyzed the joining of 3’ end of DNA that replaces

primer to rest of leading strand DNA.

7 Single-strand binding

proteins

Steps in DNA replication:

1. ________________ of DNA strands by DNA helicase by breaking the __________________.

2. _____________________________________ bind to single DNA strand and _______________ it.

• Prevents the __________________________________ until the strand are replicated.

3. Each parent strand acts as ______________ used to synthesize the ___________________ strand.

4. Both strand require _____________________ for initiation of DNA replication.

5. ______________________ catalyzed the addition of free nucleotides to pre-existing DNA strands only

from their ______________.

6. Formation of 2 identical copies of original DNA.

Explain the mechanism of DNA replication and the enzyme involved.

D B 0 1 4 | C H A P 5

4 | P a g e

1. FIGURE 1 shows DNA replication according to the semi conservative model.

FIGURE 1

a) Explain what is meant by semi conservative. [2 marks]

________________________________________________________________________

________________________________________________________________________

b) List TWO enzymes involved in DNA replication and state their functions. [4 marks]

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

c) Describe the first process in DNA replication? [2 marks]

________________________________________________________________________

________________________________________________________________________

d) Differentiate between the synthesis of leading and lagging strand during DNA

replication. [2 marks]

________________________________________________________________________

________________________________________________________________________

D B 0 1 4 | C H A P 5

5 | P a g e

2. FIGURE 2 shows a part of DNA replication.

FIGURE 2

(a) Identify strands X and Y. [2 marks]

__________________________________________________________________

________________________________________________________________

(b) Name the protein that maintains the DNA structure in FIGURE 2 to allow its

replication. [1 mark]

__________________________________________________________________

(c) Suggest the DNA replication model shown in FIGURE 2. [1 mark]

__________________________________________________________________

(d) Give TWO rules that must be obeyed for DNA replication shown in FIGURE 2.

[2 marks]

__________________________________________________________________

__________________________________________________________________

(e) Name TWO enzymes involved in the formation of strand Y. [2 marks]

__________________________________________________________________

__________________________________________________________________

(f) State the direction for formation of: [2 marks]

Leading strand: _____________________________________________________

Lagging strand: ____________________________________________________

D B 0 1 4 | C H A P 5

6 | P a g e

3. FIGURE 3 shows part of DNA replication in a eukaryotic cell

FIGURE 3

(a) Identify enzymes A and B. [2 marks]

__________________________________________________________________

__________________________________________________________________

(b) What is the function of enzymes A and B? [2 marks]

__________________________________________________________________

__________________________________________________________________

(c) What happens if enzyme A is absent in a cell? [2 marks]

__________________________________________________________________

__________________________________________________________________

(d) In FIGURE 3, label 3' end and 5' end of the lagging strand. [1 mark]

(e) How does helicase form single stranded DNA? [1 mark]

__________________________________________________________________

(f) Why is DNA replication important? [1 mark]

__________________________________________________________________

(g) State the role of C1 and C2 in DNA replication. [1 mark]

__________________________________________________________________

D B 0 1 4 | C H A P 5

7 | P a g e

Subtopic 5.3 Protein Synthesis: Transcription and Translation

Learning

Outcomes

a) Give an overview of the relationship between DNA and protein

synthesis.

b) Explain transcription which involves RNA polymerase to form

mRNA.

c) Show the relationship between codon on mRNA with sequence

of amino acid using genetic code table.

d) Explain translation of mRNA forming polypeptide chain.

Overview of the relationship between DNA and protein synthesis

D B 0 1 4 | C H A P 5

8 | P a g e

Explain transcription which involves RNA polymerase to form mRNA

Transcription:

Occur in ____________________.

The only enzyme involve is ______________________________.

Definition: __________________________________________________________________________

__________________________________________________________________________

Translation:

Occur in ____________________.

Definition: __________________________________________________________________________

__________________________________________________________________________

Characteristic of codon:

1 codon consists of ________________ nucleotide combination.

There are _______ codons in genetic code table

Only _______ codon specify amino acids

One start codon, AUG : Encodes for _________________

3 stop codons: _______________________: Termination codons

Non-overlapping

E.g : Codon 5’ AUGUCUAGU 3’ read as

________________________________________________________________________

One codon specify for ________ amino acid

One amino acid encoded by ________________________ codon(s)

D B 0 1 4 | C H A P 5

9 | P a g e

1. FIGURE 4 shows protein synthesis that occurs in eukaryotic cell.

FIGURE 4

(a) (i) Name strand C. [1 mark]

__________________________________________________________________

(ii) Other than strand C, state TWO nucleic acids that are involved in process E.

[2 marks]

__________________________________________________________________

__________________________________________________________________

(b) (i) Name processes D and E. [2 marks]

__________________________________________________________________

__________________________________________________________________

(ii) Where do processes D and E take place in cell? [2 marks]

__________________________________________________________________

__________________________________________________________________

(iii) State THREE differences between processes D and E. [3 marks]

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

D B 0 1 4 | C H A P 5

10 | P a g e

2. FIGURE 5 shows processes that take place in eukaryotic cell.

FIGURE 5

(a) Name the Process P and Q in FIGURE 5. [2 marks]

__________________________________________________________________

__________________________________________________________________

3’ – T A C G G T C A A G A C C T A – 5’

(b) Based on the above DNA sequence,

(ii) Write the mRNA sequence. [1 mark]

____________________________________________________________

(iii) How many genetic codes are found? [1 mark]

____________________________________________________________

Codon CAG CCA CUG AUG GAU GGA GUU

Amino acid Glu Pro Leu Met Asp Gly Val

(iv) Write the amino acid sequence using the genetic code given in table above.

[1 mark]

__________________________________________________________

D B 0 1 4 | C H A P 5

11 | P a g e

(c) (i) Give the function for each of the following types of RNA. [3 marks]

Types of

RNA Function

rRNA

mRNA

tRNA

(ii) What would happen if more than one ribosome are attached to a strand of

mRNA? [2 marks]

_____________________________________________________________

_____________________________________________________________

3. The table below shows the base sequence of a particular gene and amino acids coded by

the genes to form a polypeptide. [4 marks]

a) Complete the table below.

DNA sense strand TAC GCA ATC

non-template strand GGA

mRNA GUU

tRNA CGA

Amino acid Start

codon/met

gly val ala arg Stop

codon

b) Give the meaning of translation. [3 marks]

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

D B 0 1 4 | C H A P 5

12 | P a g e

c) How are aminoacyl-tRNA formed? [1 mark]

__________________________________________________________________

d) Which end of tRNA act as the amino acid binding site? [1 mark]

__________________________________________________________________

e) What are the two stages involved in protein synthesis? [1 mark]

(i) __________________________ (ii) _______________________

4. FIGURE 6 below summarizes the process of translation.

FIGURE 6

a) Name the stage of translation process shown in FIGURE 6. [1 mark]

_________________________________________________________________

b) What is meant by a codon? [1 mark]

_________________________________________________________________

A

3’ 5’

D B 0 1 4 | C H A P 5

13 | P a g e

c) Which is the first codon used in protein synthesis from this mRNA? [1 mark]

_________________________________________________________________

d) What is the anti-codon sequence in tRNA 1? [1 mark]

_________________________________________________________________

e) tRNA 1 has a 5’ – phosphate end and a 3’ – hydroxyl end. What is the function of

3’OH end in tRNA 1? [1 mark]

_________________________________________________________________

f) According to the diagram, explain what will occur to allow codon 6 to be translated.

[3 marks]

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

g) What is a polyribosome and state its importance. [2 marks]

__________________________________________________________________

__________________________________________________________________

D B 0 1 4 | C H A P 5

14 | P a g e

REVIEW QUESTIONS - Multiple Choice Questions

1. The information that is needed in the production of an enzyme is located in __________

A. DNA molecule

B. ribosome

C. nucleus

D. polysome

Use the following diagram to answer question 2

2. Where in the cell does this process take place?

A. in the nucleus

B. in the ribosome

C. in the Golgi body

D. in the rough endoplasmic reticulum.

3. What type of chemical bond is broken during the first step of replication?

A. Ionic

B. Peptide

C. Covalent

D. Hydrogen

4. The synthesis of polynucleotide chain of mRNA is catalyzed by the enzyme _____________

A. RNA helicase

B. RNA polymerase

C. DNA polymerase

D. DNA helicase

D B 0 1 4 | C H A P 5

15 | P a g e

5. In order to initiate transcription in eukaryotes

A. a core promoter sequence must be present

B. RNA strand must be present

C. RNA polymerase must be present

D. none of above

Use the following diagram to answer question 6

6. Where is structure X produced?

A. in the nucleus

B. in the nucleolus

C. in the ribosomes

D. in the endoplasmic reticulum

Use the following diagram to answer question 7, 8 and 9.

7. What process produces molecule P?

A. translation

B. replication

C. denaturation

D. transcription

molecule P

Q R

D B 0 1 4 | C H A P 5

16 | P a g e

8. What type of bond joins the structure in box Q with the structure in box R?

A. ionic

B. peptide

C. covalent

D. hydrogen

9. Name the two components which are parts of the structure shown in box Q?

A. ribose and guanine

B. ribose and cytosine

C. deoxyribose and uracil

D. deoxyribose and adenine

10. Cells of the capsulated bacteria Streptococcus pneumoniae (S strain) were crushed. Different

chemical substances were extracted from the cells and added to a nutrient medium containing

living non-capsulated bacteria (R strain). Which of the cells A, B, C or D would be

Transformed to the S strain?

S cells are crushed and chemicals are extracted

Polysaccharide Protein DNA RNA

A B C D

11. The following events occur in the replication of DNA:

1 bonds between complementary bases form

2 DNA molecule uncoils

3 opposite strands separate

4 sugar-phosphate bonds form in the new strands

5 free nucleotides align with complementary nucleotides on each strand

In which order do these events take place?

A. 2 5 3 1 4

B. 2 3 5 1 4

C. 2 5 3 4 1

D. 3 2 5 4 1

Added into culture containing living R cells

D B 0 1 4 | C H A P 5

17 | P a g e

12. What is produced during translation?

A. messenger RNA

B. steroid hormones

C. a polypeptide chain

D. new DNA molecules

13. A hormone molecule M is made up of two polypeptide chains: one chain contains 20 amino

acids and the other chain contains 31 amino acids. What is the minimum number of

nitrogenous bases in DNA required to code this molecule?

A. 51

B. 102

C. 153

D. 306

14. Which diagram shows the pairing of an RNA nucleotide with a DNA nucleotide

transcription?

A.

B.

C.

D.

D B 0 1 4 | C H A P 5

18 | P a g e

15. The table shows the anti-codon for several tRNA which are attached to a particular kind of

amino acids as given below.

Anti-codon Amino acid

3’ AGG 5’ ser

3’ AUG 5’ tyr

3’ CGC 5’ ala

3’ CGU 5’ ala

3’ GCA 5’ arg

3’ GCG 5’ arg

3’ UAC 5’ met

3’ UCC 5’ arg

3’ UGG 5’ thr

Part of the mRNA sequence produced, following transcription of the gene for a particular

polypeptide is shown.

5’ GCA GCG UAC UCC 3’

What is the correct sequence of amino acids produced when this mRNA is translated?

A. ala-ala-tyr-ser

B. ala-ala-tyr-thr

C. arg-arg-met-arg

D. arg-arg-met-thr

Use the following diagram to answer question 16, 17 and 18.

D B 0 1 4 | C H A P 5

19 | P a g e

16. Where does the synthesis of structure X occur?

A. DNA

B. Cytoplasm

C. Nucleus

D. mRNA

17. Name the amino acid that is transferred to match codon CAC.

A. Valine

B. Histidine

C. Proline

D. Leucine

18. Name the bond that joins Methionine and Phenyl-alanine.

A. Glycosidic bond

B. Hydrogen bond

C. Peptide bond

D. Phosphodiester bond

19. Which of the following is a characteristic of translation?

A. Sugar joins to phosphate groups, producing new DNA.

B. Anticodons bond to codons by complementary base pairing, producing polypeptide

chains.

C. Adenine bonds with thymine and cytosine bonds with guanine, producing mRNA.

D. Adenine bonds with uracil and cytosine bonds with guanine, producing new DNA.