Tag: bio-chemistry

Questions Related to bio-chemistry

The classical pathway of complement is activated by?

bio-chemistry diseases and immunity antibodies antibodies and antitoxin antigen and antibody

  1. Only antibody

  2. Only antigen

  3. Ag-antibody complex

  4. None of these

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Correct Option: C

Cells which actually release the antibodies are 

bio-chemistry diseases and immunity antibodies antibodies and antitoxin antigen and antibody

  1. Helper T-cells

  2. Cytotoxic T-cells

  3. Suppressor T-cells

  4. Plasma cells

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Correct Option: D
Explanation:

Antibodies are secreted by cells of the adaptive immune system; B cells, which are formed by the differentiation of the plasma cells. B lymphocytes have antibodies attached to them. Once they detect an antigen, they transform into plasma cells and secrete antibodies until the immune response is over. 

Monoclonal antibodies are

bio-chemistry diseases and immunity antibodies antibodies and antitoxin antigen and antibody

  1. Single parent type that attack many antigens

  2. Single parent type and attack specific antigen

  3. Various parent type and attack many antigens

  4. Various parent type and attack single antigen

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Correct Option: B
Explanation:

If the identical antibodies are produced by the single clone of cells such antibodies are called as monoclonal antibodies. They are clones or single type but they are target specific. Each monoclonal antibody recognizes one particular protein (antigen). They work in different ways depending on the protein they are targeting. Thus, the correct answer is option B.

Antibodies combine with antigens

bio-chemistry diseases and immunity antibodies antibodies and antitoxin antigen and antibody

  1. at variable regions

  2. at constant regions

  3. only if macrophages are present

  4. both (a) and (C)

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Correct Option: A
Explanation:

In the blood, the antigens are specifically and with high affinity bound by antibodies to form an antigen-antibody complex. The antigenic determinant or epitope is recognized by the paratope of an antibody, situated at the variable region of the polypeptide chain.

So, the correct option is 'At variable regions'.

Which one of the following statements is correct with respect to immunity?

bio-chemistry diseases and immunity antibodies antibodies and antitoxin antigen and antibody

  1. Preformed antibodies need to be injected to treat the bite by a viper snake

  2. The antibodies against small pox pathogen are produced by T-lymphocytes

  3. Antibodies are protein molecules, each of which has four light chains

  4. Rejection of a kidney graft is the function of B-lymphocytes

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Correct Option: A
Explanation:

A. Anti-snake venom is made by collecting venom from the snake and injecting small amounts of it usually into a horse. The antibodies that form in the horse blood are then collected and used to treat a snake bite case by injecting directly to the affected person.
B. Antibodies against smallpox are produced by B-lymphocytes.
C. Antibodies contain 2 light chains and 2 heavy chains.
D. Rejection of a kidney graft is a function of T-lymphocytes.

So, the correct answer is, 'Preformed antibodies need to be injected to treat the bite by a viper snake'.

Process of reverse transcription was discovered by

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

  1. Garrod

  2. Temin and Baltimore

  3. Beadle and Tatum

  4. Marshall and Nirenberg

  5. Holley and Grover

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Correct Option: B
Explanation:

Temin and Baltimore discovered reverse transcriptase or RNA dependent DNA polymerase at the same time but independently of each other. For their discovery of the viral enzyme reverse transcriptase, Howard Temin and David Baltimore shared the 1975 Nobel Prize for Physiology or Medicine. Temin discovered reverse transcriptase in Rous sarcoma virus. Baltimore arrived at the same discovery through his studies on replication of RNA containing viruses starting with poliovirus and then moving to vesicular stomatitis virus where he discovered a virion RNA polymerase. 

So, the correct answer is 'Temin and Baltimore'.

Which of the following statements is correct?

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

  1. The product of transcription is DNA

  2. The product of transcription is mRNA

  3. The product of transcription is a protein

  4. The product of translation is mRNA

  5. The product of translation is DNA

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Correct Option: B

Choose the correct answer from the alternatives given :
In some viruses, DNA is synthesised by using RNA as template. Such a DNA is called

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

  1. A-DNA

  2. B-DNA

  3. cDNA

  4. rDNA

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Correct Option: C
Explanation:

Complimentary DNA( cDNA) is DNA synthesized from a single-stranded RNA template in a reaction catalyzed by the enzyme reverse transcriptase. RNA of viruses first synthesizes complementary DNA (cDNA) through reverse transcription. DNA then transfers information to RNA which takes part in the translation of coded information to form a polypeptide. 

So, the correct answer is 'cDNA'.

The viral enzyme _________ causes the host cell to synthesize a double strand of DNA complementary to the viral RNA.

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

  1. Zymase

  2. Reverse transcriptase

  3. Enterokinase

  4. None of the above

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Correct Option: B
Explanation:

Unlike other DNA polymerases, reverse transcriptase (RT) is unique in that it is able to make a complimentary DNA strand from an RNA template. Reverse transciptases are usually found in retroviruses, which use RT to make a DNA copy of their own RNA genome, which is then incorporated into the host cell's genome. 

Zymase is an enzyme complex in yeasts that catalyzes the breakdown of sugar into alcohol and carbon dioxide.
Enterokinase is an enzyme produced by the mucosa of the small intestine. Its sole function is to activate trypsinogen to trypsin.

Therefore, the correct answer is option B.

What is a codon?

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

  1. A group of three nucleotide sequences.

  2. The nucleotide units between the start and stop codes.

  3. The nucleotide sequence that serves as the instructions for a protein.

  4. A single nucleotide in an mRNA sequence.

  5. The sequence of nucleotide that signals the start or shop of protein synthesis.

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Correct Option: A
Explanation:

A codon is defined as a sequence of three nucleotides which together form a unit of genetic code in a DNA or RNA molecule. These codon translates to form protein sequences.