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Biochemistry

Description: Basics of Biochemistry
Number of Questions: 15
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Tags: Biochemistry Questions Bio-informatics/Bio-chemistry
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What does the term 'gene' mean?

  1. DNA region which codes for a single RNA

  2. DNA region which codes for protein

  3. DNA region that codes for a single RNA or protein

  4. Fragment of chromosomes

  5. None of these

Show answer
Correct Option: C
Explanation:

It is most appropriate answer that gene is the region of DNA that codes for a single RNA or protein. Hence, this option is the correct answer.

What does the term 'genome' stand for?

  1. The complete set of genes in a cell

  2. A single gene

  3. A part of chromosome

  4. Double stranded DNA

  5. None of these

Show answer
Correct Option: A
Explanation:

Genome stands for an entire set of genes in a cell or an organelle. Hence, this option is the correct answer.

Define Chromosomal DNA.

  1. Genomic DNA of prokaryotic organisms complexed with protein

  2. Genomic DNA of eukaryotic organisms complexed with protein

  3. Genomic DNA of nearly all prokaryotic and eukaryotic organisms is complexed with protein to form chromosomal DNA

  4. Single stranded RNA

  5. A fragment of DNA

Show answer
Correct Option: C
Explanation:

It is the complete definition for chromosomal DNA.

What is the melting temperature (Tm) of DNA?

  1. The temperature at which 50% of the DNA is melted is termed the melting temperature or Tm.

  2. The temperature at which 100% of the DNA is melted is termed the melting temperature or Tm.

  3. The temperature at which DNA starts melting is termed the melting temperature or Tm.

  4. The temperature at which DNA is denatured is termed the melting temperature or Tm.

  5. All of the above

Show answer
Correct Option: A
Explanation:

This option is the correct answer. At this temperature, 50% of the DNA is melted.

Explain renaturation of DNA.

  1. Formation of a stable double-stranded DNA molecule

  2. Pairing of complementary single strands of DNA in order to form a stable double stranded DNA

  3. Separation of strands of a double stranded DNA

  4. Pairing of chromosomes

  5. All of the above

Show answer
Correct Option: B
Explanation:

Renaturation is the process in which two complementary DNA strands pair with each other to form a stable double stranded DNA. This process occurs when the melted DNA is cooled. So, the given option is true and it is the correct answer.

Explain denaturation of DNA.

  1. Separation of strands of DNA into single strands

  2. Denaturation is the separation of strands of DNA into single strands when heated to 90 degrees or above

  3. Denaturation or separation of RNA strands

  4. Denaturation or separation of DNA strands when heated to 50 degrees

  5. None of these

Show answer
Correct Option: B
Explanation:

When a DNA solution is heated to 90°C or above, there will be enough kinetic energy to denature the DNA completely, causing it to separate into single strands. So, this option is true.

Why is the value of Tm (melting temperature) more for some DNAs as compared with other DNAs?

  1. DNA which contains more adenine (A) and thymine (T) content will have more Tm value compared with other DNAs.

  2. Tm value increases with the cytosine and guanine content in the DNA.

  3. Greater the number of C-G pairs in the DNA, more will be its Tm value than the others which have more A-T pairs.

  4. Options (2) & (3) are correct

  5. None of these

Show answer
Correct Option: D
Explanation:

Yes, both the options (2) and (3) actually describe the increased Tm value for some DNAs compared with others.Hence, this option is the correct answer.

What is hybridisation of nucleic acids?

  1. The pairing of radioactively labelled RNA or DNA with the complementary strand of denatured DNA

  2. Pairing of RNA with complementary denatured DNA

  3. Pairing of radioactively labelled DNA with denatured DNA

  4. Options (1), (2) and (3) are true

  5. Pairing of chromosomes

Show answer
Correct Option: D
Explanation:

A strand of radioactively labelled RNA or DNA, when added to a denatured DNA preparation will act as a probe for DNA molecules to which it is complementary. This hybridisation of complementary strands of nucleic acid is very useful for isolating a specific fragment of DNA from a complex mixture. Hence, this option is the correct answer.

How many types of nitrogenous bases are there in nucleic acids?

  1. One

  2. Two

  3. Four

  4. Three

  5. Nitrogenous bases are not present

Show answer
Correct Option: B
Explanation:

Yes, there are two types of nitrogenous bases, purines and pyrimidines. Hence, this option is the correct answer.

What is Hyperchromic effect of DNA?

  1. Increase in the absorption of light at 260 nm as the DNA becomes denatured is known as Hyperchromic effect.

  2. Absorption of light at 260 nm by DNA is known as hyperchromic effect.

  3. DNA denaturation with the increase in temperature is known as hyperchromic effect.

  4. Both the options (1) and (2)

  5. None of these

Show answer
Correct Option: A
Explanation:

Denatured DNA have less constrained bases compared to stacked bases of double stranded DNA. So, the denatured DNA will show more absorption of light. Hence, this option is the correct answer.

Nucleoside is composed of

  1. one pentose carbon sugar and a nitogenous base

  2. a hexose sugar and a nitogenous base

  3. one pentose carbon sugar and two nitrogenous bases

  4. two pentose sugars and one base

  5. None of these

Show answer
Correct Option: A
Explanation:

Nucleosides are composed of a five membered pentose carbon sugar (2-deoxyribose sugar in DNA and ribose in RNA) and a nitrogenous base. Hence, this option is the correct answer.

What is a nucleotide?

  1. A nucleoside with a phosphate group attached at the five prime position

  2. A pentose sugar with one phosphate group

  3. A nucleoside phosphate

  4. Options (1) and (3) are true

  5. A nitrogenous base with a phosphate group

Show answer
Correct Option: D
Explanation:

A nucleoside phosphate or a nucleoside with a phosphate group attached at the 5 prime position is called a nucleotide. Hence, this option is the correct answer.

What are the names of purine and pyrimidine bases?

  1. Purines-Adenine and Cytosine; Pyrimidines-Uracil and thymine

  2. Purines-Thymine and Cytosine; Pyrimidines-Uracil and Adenine

  3. Purines-Uracil and Cytosine; Pyrimidines-Thymine

  4. Purines-Guanine and Cytosine; Pyrimidines-Uracil and Thymine

  5. Purines-Adenine and Guanine; Pyrimidines-Cytosine,Uracil and Thymine

Show answer
Correct Option: E
Explanation:

The purine bases are Adenine and Guanine while Cytosine, Uracil and Thymine are pyrimidines. Hence, this option is the correct answer.

Each strand of DNA has

  1. a free 5 prime NH2 group and a free 3 prime OH group

  2. a free 5 prime CH2 group and a free 3 prime OH group

  3. a free 5 prime OH group and a free 3 prime NH2 group

  4. a free 5 prime CO group and a free 3 prime OH group

  5. a free 5 prime OH group and a free 3 prime OH group

Show answer
Correct Option: E
Explanation:

Each strand of DNA has both a free 5 prime hydroxyl (OH) group and a free 3 prime OH group at the other end. Hence, this option is the correct answer.

RNA and DNA can be distinguished on the basis of

  1. ribose and uracil in RNA, and deoxyribose and thymine in DNA

  2. deoxyribose and uracil in RNA, and ribose and thymine in DNA

  3. ribose and thymine in RNA, and deoxyribose and uracil in DNA

  4. ribose and uracil in RNA, and deoxyribose and adenine in DNA

  5. ribose and cytosne in RNA, and deoxyribose and thymine in DNA

Show answer
Correct Option: A
Explanation:

RNA and DNA can be distinguished on the basis of the presence of ribose and uracil in RNA, and deoxyribose and thymine in DNA. Hence, this option is the correct answer.

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