Tag: bio-chemistry

Quizzes (82) Questions (1918)

Questions Related to bio-chemistry

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

In a 3.2K bp long piece of DNA, 820 adenine bases were found. What would be the number of cytosine bases

  1. 1480

  2. 740

  3. 560

  4. 780
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In double-stranded DNA, A pairs with T and G pairs with C. If there are 820 adenine bases, there must be 820 thymine bases, totaling 1640 bases. The remaining bases are 3200 - 1640 = 1560, which are split equally between G and C, so 1560 / 2 = 780 cytosine bases.

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

Teminious central dogma of protein synthesis is

  1. DNA DNA mRNA protein

  2. mRNA gRNA DNA Protein

  3. gRNA DNA mRNA Protein

  4. DNA gRNA mRNA Protein
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This represents the flow in retroviruses: genomic RNA (gRNA) is reverse transcribed to DNA, which is then transcribed to mRNA and translated to protein. Option A is standard replication, B is incorrect (gRNA to DNA requires reverse transcription), and D has incorrect flow order.

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

Central dogma of molecular biology was modified with the discovery of

  1. Ligase

  2. RNA polymerase

  3. DNA polymerase

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

The central dogma originally stated DNA to RNA to protein. The discovery of reverse transcriptase showed that RNA can serve as a template for DNA synthesis, requiring a modification to the dogma.

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

Enzyme responsible for replication of HIV in macrophages is 

  1. RNA polymerase

  2. DNA ligase

  3. DNA polymerase

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

Once inside a CD$ _4$ cell ( helper T cell ), HIV releases and uses reverse transcriptase  to convert its genetic material—HIV RNA—into HIV DNA. The conversion of HIV RNA to HIV DNA allows HIV to enter the CD$ _4$ cell nucleus and combine with the cell’s genetic material—cell DNA.

So, the correct answer is 'Reverse transcriptase'

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

Which of the following information transfers is catalyzed the reverse transcriptase?

  1. RNA $\rightarrow$ RNA
  2. RNA $\rightarrow$ DNA
  3. DNA $\rightarrow$ DNA

  4. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Reverse transcriptase is an enzyme used to generate complementary DNA (cDNA) from an RNA template, a process termed reverse transcription. A retrovirus is a type of RNA virus that inserts a copy of its genome into the DNA of a host cell that it invades thus changing the genome of that cell. Once inside the host cell cytoplasm, the virus uses its own reverse transcriptase enzyme to produce DNA from its RNA genome, the reverse of the usual pattern and thus retro (backward).

So, the correct option is ' RNA $\rightarrow$ DNA'.

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

Teminism is

  1. Central dogma reverse

  2. Central dogma of molecular biology

  3. Circular flow of hereditary information

  4. Effect of cytoplasm on functioning of DNA
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Teminism refers to the reverse of the central dogma - the flow of information from RNA back to DNA via reverse transcription. Howard Temin's work on retroviruses showed that the dogma was not unidirectional. Option B is the standard central dogma, C refers to something else, and D is unrelated.

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

Some RNA viruses carry a gene or an enzyme that uses viral RNA as a template in the synthesis of DNA. This enzyme is 

  1. RNA replicase

  2. Reverse transcriptase

  3. Viral nuclease

  4. RNA polymerase
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Reverse transcriptase catalyzes the formation of double-stranded deoxyribonucleic acid (DNA) from a single-stranded ribonucleic acid (RNA) genome. It is called "reverse" transcriptase because it reverses the usual direction of information flow, from DNA to RNA. Reverse transcriptase enzymes can be found in viruses, which use reverse transcriptase to make more viruses.

So, the correct option is 'Reverse transcriptase'.

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

In cloning experiments, cDNA molecules can be obtained from an mRNA copy by

  1. Polymerase chain reaction

  2. Reverse transcriptase

  3. Ribozyme

  4. DNA-RNA hybridization
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Complementary DNA (cDNA) is a DNA copy of a messenger RNA (mRNA) molecule produced by reverse transcriptase. cDNA is often used to clone eukaryotic genes in prokaryotes.  cDNA is also produced naturally by retroviruses (such as HIV) for integration into the host's genome.

So, the correct option is 'Reverse transcriptase'.

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

Choose the correct answers from the alternatives given :
The central dogma of molecular biology

  1. states that DNA is a template for all RNA production

  2. pertains only to prokaryotes because humans are unique

  3. states that translation precedes transcription

  4. states that DNA is a template only for DNA replication
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

During the transcription phase of the central dogma, DNA acts as the template for RNA synthesis. The RNA polymerase enzyme identifies the base on the DNA strand and adds a complementary base to the sequence. After transcription, translation of mRNA occurs that leads to the formation of the polypeptide sequence.

So, the correct option is 'states that DNA is a template for all RNA production'.