Tag: bio-chemistry

Questions Related to bio-chemistry

During transcription, the site of DNA molecule at which RNA polymerase binds is called

bio-chemistry nucleic acids central dogma transcription and gene expression molecular biology

  1. promoter

  2. regulator

  3. receptor

  4. enhancer

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Correct Option: A
Explanation:

The RNA polymerase enzyme binds to a specific site called promoter and initiates transcription. The promoter region determines which DNA strand is to be transcribed. Thus, a promoter region has RNA polymerase recognition site and RNA polymerase binding site.

The molecule needed to allow a cell to transfer genetic information from RNA to DNA, is

bio-chemistry nucleic acids central dogma transcription and gene expression molecular biology

  1. DNA polymerase

  2. RNA polymerase

  3. reverse transcriptase

  4. chlorophyll

Show answer
Correct Option: C
Explanation:

Reverse transcriptase is an enzyme used to generate complementary DNA from an RNA template, a process termed reverse transcription. Reverse transcriptase enzymes can be found in viruses, which use reverse transcriptase to make more viruses. 

So, the correct option is 'reverse transcriptase'.

Silencing of a gene could be achieved through the use of

bio-chemistry nucleic acids central dogma transcription and gene expression molecular biology

  1. RNAI only

  2. Antisense RNA only

  3. Both RNAi and antisense RNA

  4. None of the above

Show answer
Correct Option: C
Explanation:
RNAi takes place in all eukaryotic organisms as a method of cellular defense. This method involves silencing of a specific mRNA due to a complementary dsRNA molecule that binds to and prevents translation of the mRNA (silencing). The source of this complementary RNA could be from an infection by viruses having RNA genomes or mobile genetic elements (transposons) that replicate via an RNA intermediate.
So, the correct answer is 'Both RNAi and antisense RNA'.

Which of the following is correct match of phenomenon and its explanation?

bio-chemistry nucleic acids central dogma transcription and gene expression molecular biology

  1. Central dogma$\rightarrow$ RNA$\rightarrow$ DNA $\rightarrow$ Protein$\rightarrow$ RNA

  2. Reverse transcription$\rightarrow$ PCR$\rightarrow$ DNA amplification

  3. Transcription$\rightarrow$ Formation of RNA and proteins

  4. RNA silencing$\rightarrow$ Use of dsRNA

Show answer
Correct Option: B
Explanation:
Reverse transcription polymerase chain reaction (RT-PCR) uses mRNA rather than DNA as the starting template. First, the enzyme reverse transcriptase uses the mRNA template to produce a complementary single-stranded DNA strand called cDNA in a process known as reverse transcription. Next, DNA polymerase is used to convert the single-stranded cDNA into double-stranded DNA. These DNA molecules can now be used as templates for a polymerase chain reaction ( PCR ) for DNA amplification.

Central dogma can be correctly represented as DNA→ DNA→ RNA → Protein. 
Transcription is the formation of RNA from DNA. 

So, the correct option is 'Reverse transcription→ PCR→ DNA amplification'.

In reverse transcription.......... is assembled on ..........

bio-chemistry nucleic acids central dogma transcription and gene expression molecular biology

  1. mRNA, DNA

  2. DNA, agar

  3. cDNA, mRNA

  4. DNA, enzymes

Show answer
Correct Option: C
Explanation:

Complementary DNA is DNA synthesized from a single-stranded mRNA template in a reaction catalyzed by the enzyme reverse transcriptase. This process is known as reverse transcription. cDNA is often used to clone eukaryotic genes in prokaryotes. Hence it can be said that in reverse transcription cDNA is assembled on mRNA. 

So, the correct option is 'cDNA, mRNA'.

All RNA except .......... is made from DNA.

bio-chemistry nucleic acids central dogma transcription and gene expression molecular biology

  1. tRNA

  2. mRNA

  3. rRNA

  4. cDNA

Show answer
Correct Option: D
Explanation:

cDNA or complementary DNA is the DNA synthesized from a single-stranded RNA template in a reaction catalysed by reverse transcriptase enzyme. This cDNA is naturally produced by retroviruses where RNA acts as the genetic material. It is also used to clone eukaryotic genes in prokaryotes.

Remaining tRNA, mRNA and rRNA are synthesised from DNA through the process of transcription using RNA polymerase enzyme.
So, the correct option is 'cDNA'.

Which part of the cell is wrongly matched with its function?

bio-chemistry cell biology cytoplasm the components in a cell component of the cell

  1. Nucleus controls the activities of the cell

  2. Cytoplasm makes chlorophyll in green plants

  3. Cell wall protects a plant cell

  4. Cell membrane lets water and gas in and out of the cell

Show answer
Correct Option: B
Explanation:

The nucleus contains the genetic material of the cell and thus regulates all the activities of the cell.

Cytoplasm is the fluid present in the cell. It is present between plasma membrane and nucleus. it helps to maintain the shape of the cell and helps in distribution of cellular materials inside the cell.
Cell wall is a rigid covering mainly present in plant and bacterial cell and provides protection to the plant cell.
Cell membrane is a semipermeable membrane and it regulates the entry and exit of the molecules.
So, the correct answer is option B.

Which of the following is a part of protoplasm present between the nuclear membrane and cell organelle?

bio-chemistry cell biology cytoplasm the components in a cell component of the cell

  1. Leucoplast

  2. Nucleoplasm

  3. Cytoplasm

  4. None of the above

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Correct Option: C
Explanation:

Cytoplasm is a semi-fluid jelly like substance which contains various organelles and inclusions. It also contains a number of inorganic substances forming a clear true solution as well as organic substances like lipids, proteins and carbohydrates. It is homogenous and colourless in nature.

The peripheral zone of cytoplasm is thick and jelly like substance known as 

bio-chemistry cell biology cytoplasm the components in a cell component of the cell

  1. Plasmosol

  2. Nucleoid

  3. Plasmogel

  4. Plastid

Show answer
Correct Option: C
Explanation:

The peripheral zone of cytoplasm is a thick and jelly-like substance known as plasmogel. The neighbouring area of the nuclear region is thin and watery and is called as the plasmosol. It helps to regulate the amount of water needed by the cell in the cytoplasm.

So, the correct answer is option C.

A protoplast is

bio-chemistry cell biology cytoplasm the components in a cell component of the cell

  1. A cell organelle

  2. A cell with a wall

  3. A single wall-less cell

  4. Cell without nucleus

Show answer
Correct Option: C
Explanation:

Let's say, that we took a plant cell and used specific digestive enzymes to digest it's cell wall. 

After removing the cell wall, we call that cell as 'Protoplast'.
The protoplast typically consists of cytoplasm and plasma membrane but no cell wall.

Where, Cytoplasm is a fluid like substance present inside the plasma membrane and consisting of nutrients, biomolecules and all the cell organelles.
These cell organelles are such as mitochondria, ribosomes, endoplasmic reticulum, Golgi complex, Nucleus etc.

In the eukaryotic organisms such as plants and animals, nucleus is considered as the largest cell organelle.
Hence, the above explanation justifies the answer as option C  i.e., Protoplast is a single wall-less cell.