Biology

Molecular Biology and Genetics

717 Questions

Molecular biology and genetics explore the structure and function of DNA, RNA, genetic mutations, and heredity. Understanding these building blocks of life is essential for most biology examinations. Review these practice questions to test your molecular genetics knowledge.

DNA structure and basesGenetic mutationsNucleic acids compositionDNA sequencing and replication

Molecular Biology and Genetics Questions

Multiple choice

Genetic material in prokaryotes comprises

  1. circular DNA and histones

  2. linear DNA and histones

  3. circular DNA, but no histones

  4. linear DNA, but no histones
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Prokaryotes have circular DNA, but lack in proteins called histones.

Multiple choice

Which among the following BLAST programs are used to study the sequence-structure-function relationship of nucleotide sequences?

  1. Blastp
  2. MEGABLAST
  3. Blastn
  4. PSI-BLAST

  1. 1 and 2

  2. 1 and 3

  3. 2 and 3

  4. 2 and 4

  5. 3 and 4
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Comparative sequence analysis is the first step to study sequence-structure-function relationship in protein and nucleotide sequences. E.g:  Protein sequences: Blastp, PSI-BLAST and PHI-BLAST Nucleotide sequences: MEGABLAST, Discontigous-megablast and Blastn

Multiple choice

What is the sequence of nucleotides in Pribnow box?

  1. ATATTA

  2. TATAAT

  3. UAUAAT

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

The Pribnow box (also known as the Pribnow-Schaller box) is the sequence TATAAT of six nucleotides (thymine-adenine-thymine-etc.) that are essential parts of a promoter site on DNA for transcription to occur in bacteria.

Multiple choice

Which of the following characteristics differentiates DNA from RNA?

  1. Occurence of 3' deoxyribose in DNA, ribose in RNA.

  2. Occurence of uracil in RNA instead of thymidine in DNA.

  3. Existence of base pairing in DNA but not RNA.

  4. Existence of 5' phosphate in DNA but not RNA.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

It is the only correct statement. In RNA, uracil is present instead of thymidine in DNA.

Multiple choice

Which is the genetic material in living organisms?

  1. DNA

  2. ADP

  3. ATP

  4. NADP
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

DNA (Deoxyribonucleic Acid) is the primary genetic material in all cellular organisms, carrying the hereditary information in its sequence of nucleotides. While some viruses use RNA as their genetic material, DNA is the universal genetic material for all living organisms.

Multiple choice

Cytocine and guanine are held together by

  1. single hydrogen bond

  2. double hydrogen bond

  3. triple hydrogen bond

  4. None of these

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Cytosine and guanine form three hydrogen bonds between their complementary bases in DNA. This triple bonding makes the C-G pair more stable and harder to separate than the A-T pair, which has only two hydrogen bonds. This difference in bonding strength affects DNA melting temperature and stability.

Multiple choice

Which of the following statements is/are false?

a. Nucleoid has a covering of double membrane envelop. b. The DNA content in a nucleoid is equal to a single DNA molecule. c. The DNA of a nucleus is associated with histone proteins to form cromatin.

  1. Only a

  2. Only a and b

  3. Only b

  4. Only b and c

  5. Only c
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This is the correct option as this statement is false. In a nucleoid, a covering membrane is absent. It lies free in the cytoplasm.

Multiple choice

When DNA fragments with significantly different base compositions are separated and monitored by absorption spectra of UV-light, the highest peak observed is of

  1. genomic DNA

  2. satellite DNA

  3. proteins associated with DNA

  4. telomereic DNA
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When DNA fragments with significantly different base compositions are separated and monitored by absorption spectra of UV-light, the highest peak observed is of genomic DNA or bulk DNA, which is around 99% of the total DNA.

Multiple choice

Which histone molecule is found with linker DNA?

  1. H2A

  2. H2B

  3. H1

  4. H3
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

H1 histone is found with linker DNA. It is involved in chromatin compaction and sit at the base of the nucleosome near the DNA entry and exit binding to the linker region of the DNA.

Multiple choice

What is the modern concept of a gene?

  1. It is a segment of DNA capable of crossing over.

  2. It is a functional unit of DNA.

  3. It is a segment of DNA.

  4. It is a segment of chromosome.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

According to the modern concept, gene is a functional unit of DNA.

Multiple choice

Assertion (A): Under alkaline conditions, DNA is more stable than RNA. Reason (R): RNA is more susceptible to base-catalysed hydrolysis than DNA.

Directions: In the following question there are two statements, Assertion (A) and Reason (R), consider both the statements independently and mark your answers as under:

1. If A and R both are correct and R is the correct explanation of A.
2. If A and R both are correct and R is not the correct explanation of A.
3. If A is correct and R is incorrect.
4. If A is incorrect and R is correct.
5. If A and R both are incorrect.

  1. 1

  2. 2

  3. 3

  4. 4

  5. 5
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This is the correct answer.

Multiple choice

How many Protein coding genes might be present in the Human Genome?

  1. 10, 000

  2. 40, 000

  3. 80, 000

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

The Human Genome Project initially estimated approximately 30,000-40,000 protein-coding genes, with more refined current estimates placing the number around 20,000-25,000. Option B (40,000) represents an older but widely cited estimate from the early genomic era. The question uses 'might be' suggesting approximation rather than precision, making 40,000 a reasonable answer choice in the context of ongoing scientific discovery and gene identification methods.

Multiple choice

Nucleotides are building blocks of nucleic acids. Each nucleotide is a composite molecule formed by

  1. base-sugar-OH

  2. base-sugar-phosphate

  3. sugar-phosphate

  4. (base-sugar-phosphate)n
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

 A nucleotide is one of the structural components or building blocks of DNA and RNA. A nucleotide consists of a base (one of four chemicals: adenine, thymine, guanine, and cytosine) plus a molecule of sugar and one of phosphoric acid.