Questions

Case study (4 Marks)

Take a timed test

2 questions · self-marked practice — reveal the answer and mark yourself.

Question 14 Marks
Read the following text carefully and answer the questions that follow:
Transgenic animals can serve as factories that in some cases, may produce large amounts of proteins more efficiently. Transgenic mice have been engineered to express human antibodies by introducing a large segment of human DNA encoding human immunoglobulin genes. In transgenic large animals such as cows or sheep proteins of pharmaceutical value can be produced in large quantities in milk which is later purified. Transgenes can be used to alter many phenotypic properties including growth rate, fat composition, milk production, hair texture, etc.
i. In transgenic animals, i.e. cow and sheep proteins of pharmaceutical value are produced in large quantities in which gland. (1)
ii. Why is mouse the most preferred animal for studies on gene transfer? (1)
iii. Why does the production of transgenic animals take place? (2)
OR
Assertion (A): Transgenic mice have been engineered to express human antibodies. (2)
Reason (R): Large segments of human DNA encoding human immunoglobulin have been transferred to mice.
a. Both A and R are true and R is the correct explanation of A.
b. Both A and R are true but R is not the correct explanation of A.
c. A is true but R is false.
d. A is false but R is true.
Answer
i. Mammary gland
ii. Short oestrus cycle.
iii. a. All of these Identification and separation of desired gene.
b. Combining the desired gene with appropriate vector.
c. Introduction of vector in cells, tissues or embryos.
OR
(a) Both A and R are true and R is the correct explanation of A.
View full question & answer
Question 24 Marks
Read the following text carefully and answer the questions that follow:
Gene regulation is the mechanism of switching off and switching on of the genes depending upon the requirement of cells and the state of development. Gene regulation is of two types: negative and positive. In negative gene regulation, the genes continue expressing their effect till their activity is suppressed. Positive gene regulation is the one in which the genes remain non-expressed unless and until they are induced to do it. Operon model is a co-ordinated group of genes such as structural gene, operator gene, promoter gene, regulator gene which function together and regulate a metabolic pathway as a unit, e.g., lac operon, trp operon, ara operon, etc.
Image
i. Regulation of gene expression occurs at which the level? (1)
ii. What is complementary to an mRNA molecule transcribed from the lac operon contains nucleotide sequences? (1)
iii. Describes the control of transcription of the genes involved in the breakdown of lactose in Escherichia coli?
(2)
OR
What is the function of catabolic activator protein in lac operon? (2)
Answer
i. Regulation of gene expression can be exerted at four levels: transcriptional level during formation of primary transcript, processing like splicing, terminal additions or modifications, transport of mRNAs from nucleus to the cytoplasm and translational level.
ii. Only the structural genes of an operon are transcribed into mRNA molecule. Structural gene is a region of DNA that codes for a protein or RNA molecule that forms part of a structure or has an enzymatic function. In the case of lac operon, the structural genes are lac Z, lac Y, lac A which codes for $\beta$-galactosidase, lac permease and $\beta$-galactoside transacetylase respectively.
iii. The lac operon consists of:
Promoter: binding site of RNA polymerase
Operator: binding site of the lac repressor protein
CAP Binding Site: binding site of catabolite activator protein.
3 structural genes: lac Z, lac Y and lac A. When lac repressor protein is synthesised in its active conformation, it binds to the operator and the operon is switched off, so there is no transcription.
OR
The function of catabolic activator protein in lac operon is to activates lac gene when glucose is absent.
View full question & answer