Tag: inherited changes

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Questions Related to inherited changes

Multiple choice expression of gene inherited changes biology

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

  1. Cistron

  2. Recon

  3. Operon

  4. Muton
Reveal answer Fill a bubble to check yourself
C Correct answer
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.
Multiple choice expression of gene inherited changes biology

Operon contains

  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
Reveal answer Fill a bubble to check yourself
D Correct answer
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'.

Multiple choice expression of gene inherited changes biology

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

  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.
Reveal answer Fill a bubble to check yourself
A Correct answer
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.'

Multiple choice expression of gene inherited changes biology

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

  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.
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

Multiple choice expression of gene inherited changes biology

Genes that are involved in turning on or off the transcription of a set of structural genes are called as

  1. Polymorphic genes

  2. Operator genes

  3. Redundant genes

  4. Regulatory genes
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Regulator gene regulates the expression of structural genes by its protein products 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; option D is correct. Operator is a DNA sequence present between the promoter region and the first coding gene. This operator region serves as repressor protein binding site; option B is wrong. Genes which govern more or less same trait or perform same role are called redundant genes; presence of these genes confers advantage of diluting the effect of point mutation on organisms; option C is wrong. Presence of more than one allele on a genetic locus is called gene polymorphism provided that the allele is present with more than 5% frequency in the population; option A is wrong. 

Multiple choice expression of gene inherited changes biology

A specific nucleotide sequence to which RNA polymerase attaches to initiate transcription of mRNA, is the sequence of which gene?

  1. Promoter gene

  2. Structural gene

  3. Operon

  4. Regulator gene
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In genetics, a promoter is a region of DNA that initiates transcription of a particular gene. Promoters are located near the transcription start sites of genes, on the same strand and upstream on the DNA (towards the 5' region of the sense strand).

Multiple choice expression of gene inherited changes biology

According to the operon concept, the regulatory gene regulates the chemical reactions of the cell by

  1. Inactivating enzymes in the reaction

  2. Inhibiting transcription of mRNA

  3. Inhibiting migration of mRNA into cytoplasm

  4. Inhibiting the substrate in the reaction
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

An operon is a functioning unit of genomic DNA containing a cluster of genes under the control of a single promoter. The genes are transcribed together into an mRNA strand and either translated together in the cytoplasm, or undergo trans-splicing to create monocistronic mRNAs that are translated separately. Regulator gene regulates inhibiting transcription of mRNA.

Multiple choice expression of gene inherited changes biology

Regulated unit of genetic material is termed as

  1. Operon

  2. Regulator gene

  3. Operator gene

  4. Okazaki segment
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

An operon is a cluster of genes under the control of a single promoter, functioning as a regulated unit of genetic material in prokaryotes.

Multiple choice expression of gene inherited changes biology

Tryptophan operon of Escherichia coli is

  1. Monocistronic

  2. Inducible

  3. Unregulated

  4. Repressible
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The tryptophan operon is a repressible operon, meaning it is normally active and is turned off when the end product (tryptophan) is present in sufficient quantities.

Multiple choice expression of gene inherited changes biology

Which is correct

  1. Both animal and plant cells have a well defined cell wall

  2. Cells are formed de novo from abiotic materials

  3. Cells of all living organisms have a nucleus

  4. In prokaryotes there are no membrane bound cell organelles.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Prokaryotic cells lack membrane-bound organelles like the nucleus, mitochondria, or chloroplasts, which is a defining characteristic distinguishing them from eukaryotic cells.