Tag: expression of gene

Questions Related to expression of gene

In eukaryotes, which of the following genes synthesise heterogeneous nuclear RNA 

expression of gene inherited changes biology

  1. Holandric genes

  2. Split genes

  3. A-genes

  4. Z-genes

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Correct Option: B

Which one of the following is NOT a component of lactose operon in bacteria?

expression of gene inherited changes biology

  1. Operator

  2. Repressor

  3. Regulator

  4. Structural gene

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Correct Option: A

The smallest unit of DNA capable of coding for the synthesis of a polypeptide is the ___________.

expression of gene inherited changes biology

  1. Operon

  2. Promoter

  3. Cistron

  4. Replicon

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Correct Option: A

In eukaryotes, removal of RNA polymerase III from nucleoplasm will affect transcription of  

expression of gene inherited changes biology

  1. mRNA

  2. hnRNA

  3. tRNA

  4. 5.8 S rRNA

  5. 18 S rRNA

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Correct Option: C

In Negative operon : -

expression of gene inherited changes biology

  1. Inducer binds with repressor

  2. Co-repressor does not binds with repressor

  3. Corepressor binds with inducer

  4. CAMP have negative effect on lac operon

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Correct Option: A
Explanation:
The inducer is a molecule that regulates gene expression. An inducer can bind to protein repressors or activators. The lac operon is a negatively controlled inducible operon, where the inducer molecule is Lactose. If the inducer molecule is present, it binds to the repressor and changes its conformation so that it is unable to bind to the operator and thus gene expression is controlled.
So, the correct answer is 'Inducer binds with repressor'.

The function of a repressor protein in an operon system is to prevent protein synthesis by binding to ________________.

expression of gene inherited changes biology

  1. The ribosome

  2. The RNA polymerase, thus blocking transcription

  3. A specify region of the mRNA, preventing translation to protein

  4. A specific region of the operon, preventing transcription of structural genes

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Correct Option: A

How many of the following statements are correct
(A) In prokaryotes, control of the rate of transcriptional initiation is the predominant site for control of gene expression
(B) Lac operon is under negative regulation of CAP.
(C) Presence of intron is reminiscent of antiquity.
(D) Inheritance of a character is also affected by promoter and regulatory sequence of a structural gene.

expression of gene inherited changes biology

  1. $2$

  2. $3$

  3. $4$

  4. $5$

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Correct Option: B

Regulator gene controls chemical synthesis(Operon concept) by.

expression of gene inherited changes biology

  1. Inhibiting transcription

  2. Inhibiting enzymes

  3. Inhibiting passage of mRNA

  4. Inhibiting substrate enzyme reaction

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Correct Option: A

Read the following four statements (A-D) :
(A) In transcription, adenine pairs with uracil.
(B) Regulation of lac operon by repressor is referred to as positive regulation.
(C) The human genome has approximately 50,000 genes.
(D) Haemophilia is a sex-linked recessive disease.
How many of the above statements are correct?

expression of gene inherited changes biology

  1. Three

  2. Four

  3. One

  4. Two

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Correct Option: D
Explanation:
A. Transcription is the process of synthesis of RNA from a template DNA by the replicative enzyme RNA polymerase. As we know, purine bases pair with pyrimidine bases i.e. Adenine pairs with Thymine or vice versa and Guanosine pairs with Cytosine or vice versa. Since RNA has Uracil instead of Thymine, Adenine pairs with Uracil in transcription. Hence, statement A is correct.
B. The regulation of lac operon by repressor is negative regulation as in the presence of repressor (lactose in case of E. coli), the transcription of the structural gene doesn't occur because repressor binds to the operator region and due to this, RNA polymerase can't proceed transcription. Hence, statement B is incorrect.
C. Human genome has approximately 30,000-40,000 genes. Hence, statement C is incorrect. 
D. Haemophilia is a sex linked disorder. It is a X-linked recessive disease which is caused by a recessive gene located on X chromosome. Hence, statement D is correct.
So, out of all statements given in the question, statements A and D are correct.
So, the correct answer is 'Two'. 

Which one of the following is wrong:

expression of gene inherited changes biology

  1. $Y$ in Lac Operon is responsible for $\beta$ galactoside permease

  2. In Lac-operon the repressor becomes inactive if it binds with lactose

  3. In repressible control of gene action the repressor cannot bind to promotor if co repressor is present

  4. Tryptophan operon consists of five structural genes

  5. The mRNA produced from a bacterium is usually polycistronic

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Correct Option: A