Tag: biology

Questions Related to biology

Initiating codon in eukaryotes is

expression of gene inherited changes biology

  1. AUG

  2. GUG

  3. UGA

  4. UAG

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Correct Option: A

Inheritance of a character is also affected by the promoter and regulatory sequences of a structural gene. Hence, sometimes the regulatory sequences are loosely defined as 

expression of gene inherited changes biology

  1. Structural gene 

  2. Regulatory gene

  3. Promoter gene

  4. None of the above

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Correct Option: B
Explanation:
A regulatory gene is a gene involved in controlling the expression of one or more other genes. Regulatory sequences encode regulatory genes. Sometimes the regulatory sequences are loosely defined as regulatory genes because the regulatory sequences of a structural gene affect the inheritance of a character.
So, the correct answer is 'Regulatory gene'.

Functioning of structural genes is controlled by

expression of gene inherited changes biology

  1. Operator

  2. Ligase

  3. Regulator gene

  4. Polymerase

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Correct Option: C
Explanation:

Operon can be defined as DNA segment having a cluster of genes which are controlled by single promoter. It consists of operator gene and structural genes. The operator gene regulates the expression of structural genes by providing a binding site to transcription factor which in turn regulate the gene expression by altering the binding of RNA polymerase to the promoter region. A promoter is a DNA segment where transcription of a particular gene starts. The regulator genes code for transcription factor/repressor proteins that binds to operators or promoters and prevent RNA polymerase from transcribing RNA. The alteration in repressor proteins by inducers make them unable to bind DNA and allow RNA polymerase to carry out transcription. Thus regulator gene control the functioning of structural genes via operator gene. Option C is correct answer.

Gene which is responsible for the synthesis of a polypeptide chain is called as

expression of gene inherited changes biology

  1. Promotor gene

  2. Structural gene

  3. Regulator gene

  4. Operator gene

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Correct Option: B
Explanation:

Promoter is a DNA segment that serves to initiate transcription of a particular gene. They are present upstream near the transcription start sites of genes. Regulator gene regulates the expression of structural genes by its protein product that are mostly transcription factors. These transcription factors bind to the operator region which is located just upstream the binding site of the RNA polymerase and hence, prevent the binding and transcription. Operator is a DNA sequence present between the promoter region and the first coding gene. This operator region serves as repressor protein binding site. The gene that codes for any RNA / protein product which do not serve as regulatory protein are known as structural genes. The lac Z lac Y and lac A genes in lac operon are the structural genes. Option B is the correct answer.

Functioning of structural genes is controlled by

expression of gene inherited changes biology

  1. Operator

  2. Promoter

  3. Ligase

  4. Regulator gene

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Correct Option: D
Explanation:

Operon can be defined as DNA segment having a cluster of genes which are controlled by single promoter. It consists of operator gene and structural genes. The operator gene regulates the expression of structural genes by providing a binding site to transcription factor which in turn regulate the gene expression by altering the binding of RNA polymerase to the promoter region. A promoter is a DNA segment where transcription of a particular gene starts. Ligase enzymes facilitate the joining of two DNA strand together by phosphodiester bonds. The regulator genes code for transcription factor/repressor proteins that binds to operators or promoters and prevent RNA polymerase from transcribing RNA. The alteration in repressor proteins by inducers make them unable to bind DNA and allow RNA polymerase to carry out transcription. Thus regulator gene control the functioning of structural genes via operator gene. Option D is correct answer.

Which of the following hormones control gene expression?

expression of gene inherited changes biology

  1. growth hormone

  2. prolactin

  3. oxytocin

  4. thyroxine

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Correct Option: A
Explanation:

  • Growth hormone helps in amino acid uptake in all the tissues and also help in the transcription process in which DNA is converted into mRNA.
  • GH also help in synthesis of protein hormone.
  • It also helps to decrease protein catabolism.
Hence, the correct answer is 'Growth hormone'

A co-ordinated unit which controls the genetic expression is called as a/an

expression of gene inherited changes biology

  1. Cistron

  2. Recon

  3. Operon

  4. Muton

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Correct Option: C
Explanation:
Cistron: Is a section of a DNA or RNA molecule that codes for a specific polypeptide in a protein synthesis.
Recon: In a cistron, the recombinational units may be more than one. Thus, the smallest unit capable of undergoing recombination is called as a recon.
Muton: It may be defined as, "the smallest unit of DNA which may be changed is the nucleotide''. Therefore, cistron is the largest unit in size followed by recon and muton. This can be explained that a gene consists of several cistron, a cistron contains many recons and a recon contains a number of mutons. 
Operon: It is a unit of genetic material that functions in a co-ordinated manner by means of an operator, a promoter and one or more structural genes that are transcribed together.
Thus, the correct answer is option C.

Operon contains

expression of gene inherited changes biology

  1. Operator and regulator genes

  2. Operator and structural genes

  3. Operator, regulator genes and repressor

  4. Operator gene, regulator gene, repressor gene, structural genes and promoter gene

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Correct Option: D
Explanation:

  • Operator gene is a segment of DNA present between the promoter and the genes of the operon. It helps in transcribing the genes of the operon.
  • Regulator gene often codes for repressor proteins which bind with the operator and checks the operon.
  • Repressor gene physically obstructs the RNA polymerase from transcribing the genes by binding with the operator gene.
  • Structural genes are the genes that undergo translation to produce enzymes and are co-regulated by the operon.
  • Promoter gene is a nucleotide sequence that enables a gene to be transcribed. It is recognized by RNA polymerase, which then initiates transcription.
So, the correct option is 'Operator gene, regulator gene, repressor gene, structural genes and promoter gene'.

Which of the following is an example of positive gene regulation?

expression of gene inherited changes biology

  1. The tryptophan gene, in which the presence of tryptophan functions as a corepressor to prevent its own transcription.

  2. The lac gene, in which the repressor preventing the synthesis of the enzymes that degrade lactose is deactivated by the presence of lactose.

  3. CAP, which acts as a required transcription factor for the enzymes that degrade lactose.

  4. All of the above.

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Correct Option: A
Explanation:

Regulation of functioning of the expression of genes is known as the regulation of gene expression. It is basically of three types- inducible, constitutive and repressible.

The repressible kind of control is when the product of regulatory gene initiates the expression of the gene under its control.
The tryptophan consists of repressible Operon model in which when the end product tryptophan is present in sufficient amount it's molecules act as corepressor and the structural genes become switched this is also known as feedback repression or positive regulation.

So, the correct option is 'The tryptophan gene, in which the presence of tryptophan functions as a corepressor to prevent its own transcription.'

RNA polymerase which is on the promoter, moves to the structural genes to transcribe them. However, it happens when

expression of gene inherited changes biology

  1. RNA polymerase shifts first to regulator gene.

  2. Inducer binds to structural genes.

  3. There is repressor on the operator.

  4. There is no repressor on the operator.

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Correct Option: D
Explanation:

The promoter is a DNA segment that serves to initiate transcription of a particular gene. They are present upstream near the transcription start sites of genes. Regulator gene regulates the expression of structural genes by its protein product that is mostly transcription factors, also termed as the repressor. The operator is a DNA sequence present between the promoter region and the first coding gene. This operator region serves as a repressor protein binding site. The repressor binds to operator region which is located just upstream the binding site of the RNA polymerase and hence, prevent the binding and transcription; this makes option C incorrect. Regulator gene serves to regulate the expression of structural genes via repressor; it does not provide the binding site for RNA polymerase; option A is wrong. The inducer is a molecule that binds to repressor to prevent its binding to operator region and thereby, facilitates gene expression; option B is incorrect.