All questions of Gene Regulation and Mutation for Grade 9 Exam
In E. coli, the lac operon gets switched on when- a)Lactose is present and it binds to the repressor
- b)RNA polymerase binds to the operator
- c)Lactose is present and it binds to RNA polymerase
- d)Repressor binds to operator
Correct answer is 'A'. Can you explain this answer?
In E. coli, the lac operon gets switched on when
a)
Lactose is present and it binds to the repressor
b)
RNA polymerase binds to the operator
c)
Lactose is present and it binds to RNA polymerase
d)
Repressor binds to operator
|
Geetika Shah answered |
In case of lactose presence
(i) Lactose acts as an inducer which binds to the repressor and forms an inactive repressor.
(ii) The repressor fails to bind to the operator region.
(iii) The RNA polymerase binds to the operator and transcript lac mRNA.
(iv) lac mRNA is polycistronic, i.e., produces all three enzymes, β -galactosidase, permeaseand transacetylase.
(v) The lac operon is switched on.
In case of lactose absence
(i) When lactose is absent, i gene regulates and produces repressor mRNA which translate repression.
(ii) The repressor protein binds to the operator region of the operon and as a resultprevents RNA polymerase to bind to the operon.
(iii) The operon is switched off.
During splicing, the exons are joined and the enzyme which catalyses this reaction is- a)RNA ligase
- b)RNA polymerase
- c)RNA catalase
- d)RNA permease
Correct answer is option 'A'. Can you explain this answer?
During splicing, the exons are joined and the enzyme which catalyses this reaction is
a)
RNA ligase
b)
RNA polymerase
c)
RNA catalase
d)
RNA permease
|
Ved Patidar answered |
Joint joining of nucleotide in RNA and DNA is done by DNA/RNA ligase.
Can you explain the answer of this question below:Repressor protein is produced by
- A:
Operator gene
- B:
Promotor gene
- C:
Structural gene
- D:
Regulator gene
The answer is d.
Repressor protein is produced by
Operator gene
Promotor gene
Structural gene
Regulator gene
|
Rajat Kapoor answered |
In prokaryotes, regulator genes often code for repressor proteins. Repressor proteins bind to operators or promoters, preventing RNA polymerase from transcribing RNA. They are usually constantly expressed so the cell always has a supply of repressor molecules on hand.
Repressor protein is produced by- a)Operator gene
- b)Promotor gene
- c)Structural gene
- d)Regulator gene
Correct answer is 'D'. Can you explain this answer?
Repressor protein is produced by
a)
Operator gene
b)
Promotor gene
c)
Structural gene
d)
Regulator gene
|
Nidhi Nambiar answered |
Regulator gene controls the expression of operon and produces a small protein molecule known as repressor. It is a DNA or RNA binding protein that inhibits the expression of one or more genes by binding to the operator or associated silencers. It blocks the attachment of RNA polymerase to the promoter.hence, it prevents translation of mRNA into protein and this entire process is known as repression.
In the Lac operon system, β-galactosidase is coded by- a)y-gene
- b)I-gene
- c)z-gene
- d)a-gene
Correct answer is option 'C'. Can you explain this answer?
In the Lac operon system, β-galactosidase is coded by
a)
y-gene
b)
I-gene
c)
z-gene
d)
a-gene
|
Jatin Chakraborty answered |
The gene product of lacZ is beta-galactosidase which cleaves lactose, a disaccharide, into glucose and galactose. LacY encodes Beta-galactoside permease, a membrane protein that becomes embedded in the cytoplasmic membrane to enable the cellular transport of lactose into the cell.
The lac operon consists of- a)One regulatory gene and three structural genes
- b)Two regulatory genes and two structural genes
- c)Three regulatory genes and three structural genes
- d)Four regulatory genes only
Correct answer is option 'A'. Can you explain this answer?
The lac operon consists of
a)
One regulatory gene and three structural genes
b)
Two regulatory genes and two structural genes
c)
Three regulatory genes and three structural genes
d)
Four regulatory genes only
|
Syed Hussain answered |
It consists of three adjacent structural genes, a promoter, a terminator, and anoperator. The lac operon is regulated by several factors including the availability of glucose and lactose. It can be activated by allolactose. Lactose binds to the repressor protein and prevents it from repressinggene transcription.
The diagram shows an important concept in the genetic implication of DNA. Fill in the blanks A to C.
- a)A – transcription B – translation C – Francis Crick
- b)A – translation B – extension C – Rosalind Franklin
- c)A – transcription B – replication C – James Watson
- d)A – translation B – transcription C – Erwin Chargaff
Correct answer is option 'A'. Can you explain this answer?
The diagram shows an important concept in the genetic implication of DNA. Fill in the blanks A to C.
a)
A – transcription B – translation C – Francis Crick
b)
A – translation B – extension C – Rosalind Franklin
c)
A – transcription B – replication C – James Watson
d)
A – translation B – transcription C – Erwin Chargaff
|
Maitri Mukherjee answered |
The process by which RNA is synthesised from DNA is transcription. Hence, A is transcription.
The process by which proteins are made from mRNA is translation. Hence, B is translation.
This scheme represents Central dogma of molecular biology which was proposed by Francis Crick.
So, the correct answer is 'A-transcription, B-translation, C-Francis Crick'
Which one of the following enzyme brings about hydrolysis of lactose to glucose and galactose?- a)Transacetylase
- b)Amylase
- c)β-galactosidase
- d)Permease
Correct answer is option 'C'. Can you explain this answer?
Which one of the following enzyme brings about hydrolysis of lactose to glucose and galactose?
a)
Transacetylase
b)
Amylase
c)
β-galactosidase
d)
Permease
|
Stepway Academy answered |
The lac operon consists of the following parts:
- Structural Gene - It consists of 3 genes:
- z - codes for β-galactosidase
- y - codes for permease
- a - codes for transacetylase
- Operator -
- It is present adjacent to the structural gene.
- It is the site for the binding of repressor protein.
- Regulator -
- It comprises of the i-gene, which codes for the repressor protein.
- The repressor protein is synthesized all the time constitutively.
- Promoter -
- It is the transcription initiation site where RNA polymerase binds.
- Inducer -
- It is the molecule that determines whether the repressor will bind to the operator or not.
- Hence, it regulates the operon.
- Example - Lactose in lac operon.
Select the correct match- a)Alec Jeffreys - Streptococcus pneumoniae
- b)Francois Jacob and Jacques Monod - Lac operon
- c)Alfred Hershey and Martha Chase - TMV
- d)Matthew Meselson and F. Stahl - Pisum sativum
Correct answer is option 'B'. Can you explain this answer?
Select the correct match
a)
Alec Jeffreys - Streptococcus pneumoniae
b)
Francois Jacob and Jacques Monod - Lac operon
c)
Alfred Hershey and Martha Chase - TMV
d)
Matthew Meselson and F. Stahl - Pisum sativum
|
|
Stepway Academy answered |
Option 1:
- Alec Jeffreys discovered a technique known as DNA fingerprinting. It is used for the identification of organisms based on their DNA profiles.
- Streptococcus pneumoniae is a gram-positive anaerobic bacterium that causes pneumonia. It also causes middle ear infections in children.
Option 2:
- Francois Jacob and Jacques Monod discovered the lac operon.
- Lac operon or lactose operon is found in E. coli for the metabolism of lactose and its utilization and uptake.
- Genes in lac operon code for a protein that allow them to use lactose as a source of energy.
Option 3:
- Hershey and Chase experimented to prove that DNA is the genetic material. They used bacteriophages to perform this experiment. Bacteriophages are viruses that infect bacteria.
- TMV stands for tobacco mosaic virus. It contains a single-stranded RNA virus that causes mosaic disease in tobacco. This virus affects tomatoes also.
Option 4:
- Mathew Meselson and F. Stahl discovered the semi-conservative nature of DNA replication. It means that during DNA replication, one new strand and one old strand are synthesized.
- Pisum sativum, a pea plant was used by Mendel to carry out his genetic experiments. He took seven contrasting characters of Pisum sativum and carried out crossing experiments for several generations to understand the inheritance pattern of genes.
So, the correct answer is option 2.
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